Talk:Global Positioning System/Archive 2

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Postings last commented on in January 2007

Dates and Year Links

Does every date and year need to be linked? I find the over-use of links to be distracting and unnecesary. Do I really need to read an article about February 14th or 1989 to understand this sentence: "The first of 24 satellites that form the current GPS constellation (Block II) was placed into orbit on February 14, 1989." 66.75.48.79

When I looked at the article, I found the February 14 reference had already been changed to just "February", but there was a similar reference for the most recently launched satelite, September 25. When I checked the link, there was no reference on that page to the satelite launch event, so I unlinked the date. If anything, the date of the first satelite launch is probably more link-worthy than the most recent one. Michaelfavor 17:38, 17 January 2006 (UTC)

Linking years alone, such as 2006, or months alone, such as November 8 is pointless and violates Wikipedia style guidelines. However, linking a complete date, such as November 11 2006 has an entirely different purpose: The Wikipedia engine uses it to automatically format the date for presentation according to the reader's preferences. By default, the given example would produce "November 11, 2006". In my preferences I selected [day month year] format, so I would see "11 November 2006" when reading the same article. The entire article could be written with a variety of legal date formats, and as long as they were wikified in every instance, I would see all dates in my preferred format.
That said, I've written a macro for my word processor that I regularly use to quickly strip out year links in articles and I tag the edit summary with the following boilerplate for date overlinking:

removed [[WP:MOSDATE#Date_formatting|date overlinking]]

—Quicksilver^{T @} 19:14, 8 November 2006 (UTC)

Relativity correction performed by the receiver

While I was looking into the various ways that relativity is accounted for in the Global Positioning System, I came across one correction which should probably be mentioned here. Nearly all of the relativity effects are accounted for at the control station and in the clock frequencies, but there is a small correction which takes place in the receiver.

The satellite orbits are slightly elliptical (e=0.02) which causes the velocity of the satellites and their positions relative to earth to change over their complete orbits. It is my understanding that the relativity effect arising from the elliptical orbit is slight (it could lead to a ranging error of ~14 meters out of more than 20,000 km). It is also regular and easily predictable. I read a few sources which state that a correction factor is included in the satellite message and these corrections are performed in the receiver software. As a result, they're invisible in most user applications. Search for "eccentricity" in these sources: [1], [2] (see The Eccentricity Correction section), and [3]. - Justin 18:26, 26 October 2006 (UTC)

I'm sad to say it, but my predictions are coming true: more bullshit is creeping back into this article. From the "Relativity" section, I read:

GPS receivers typically do not need to make any relativistic corrections because the errors introduced by relativistic effects on the recievers are negligible--less than one centimeter, for receivers on or near the earth's surface.[15]

The cited reference connects the claim not to receivers, but to the elements of the control segment of the GPS system. As you have correctly pointed out (and I mentioned a few weeks ago, see above), the receivers do apply a by-the-book relativistic eccentric correction, amounting to some 15 metres. I am asking the author of the above sentence to re-write it to reflect the contents of the source he is quoting, or, in the alternative, simply remove it altogether. mdf 20:18, 26 October 2006 (UTC)

It seems that one of the problems is that, AFAIK, the sentence you cite from the article is halfway correct: the GPS system ,more specifically the GPS recievers, does not do any corrections for the relativistic effects on the recievers themselves. What some people seems to have a hard time understanding is that this does not imply that there is no correction being done for relativistic effects on the satellites: In reality compensation for this is done both in the satellites and in the recievers.Mossig 20:48, 26 October 2006 (UTC)

I wrote the sentence.. You understand it, you fix it.  :) Pfalstad 21:13, 26 October 2006 (UTC)

OK. Please check so it is acceptable. Mossig 21:17, 26 October 2006 (UTC)

I think it was still wrong according to the above. I fixed it. mdf, if you see bullshit in the article, please fix it, don't just complain about it on the talk page.. You understand it better than I do. Pfalstad 17:00, 1 November 2006 (UTC)

Reality...

Folks - whatever corrections are needed to keep the GPS satellite broadcast information on track are handled by ground stations that monitor the difference between what's broadcast and a know, surveyed position. Clock and position corrections are fed to the satellites as required so that the signals received on the ground by normal GPS receivers remain fairly tight. That's just the way the system works. The receivers themselves don't do any additional complex calculations. Rather, they rely on the GPS system's internal integrity checks. In addition, WAAS is available across nearly all of North America, and further refines position accuracy by means of a number of additional ground stations and two additional satellites which feed correction data back to WAAS-enabled receivers. The primary benefit of WAAS is an increase in the accuracy of the altitude, and not necessarily the 2D positional accuracy (although some benefit is gained there, as well). Bottom line, please report the facts, cite verifiable references, and UNLOCK this account. I will monitor regularly (it's now on my watchlist) to ensure that what's reported actually pertains to reality within the GPS world. I'm sure quite a few others here will be doing the same. Thanks. Mugaliens 16:26, 6 October 2006 (UTC)

You underestimate the presence level and consequently the power of the Einstein trolls on the Internet and in other media.

Just for the sake of what I'm sure will be an interesting response, what are your scientific credentials, and how did you come to arrive at the truth about Einstein and his "Theory" of Relativity? Enlighten the trolls, please. Justin 04:00, 8 October 2006 (UTC)

I'm an engineer who helped design WAAS, am working on [LAAS] and am a consultant for the Joint Precision Approach and Landing System. I have seventeen and a half years of experience designed and using GPS systems and equipment. I'm also a pilot. Mugaliens 13:23, 1 November 2006 (UTC)

This is my first exposure to anti-Einstein trolls. They're clearly nuts. Anyone who uses the phrase "only a theory" must be unaware of the nature of theories. Theories do not earn that name until they are strongly supported by observation. It might be reasonable to say that an idea is "only a hypothesis", but when one says "only a theory", as the Intelligent Design folks are fond of doing with respect to Evolution, one only displays one's own ignorance. Einstein's theories of Special and General Relativity are as carefully tested (and completely verified), as anything in Physics. Every prediction made by the theories has been verified, from the earliest ones that predated any method of verifying them, right up to the recent work on the cosmic background microwave radiation by George Smoot, which earned him this year's Nobel prize. The theories work to the last available decimal place. The predictions made by Relativity that did not match the experimental evidence number exactly zero. This is bedrock stuff. The other evidence of the trolls' unscientific thinking is their confusion of the term "theory" and "law". They apparently suffer from the junior-high-school notion that when theories grow up, and gain support, they metamorphose into laws. Theories never become laws; they are different things. Laws describe the way the universe behaves, with no attempt to explain the reason. The Law of Gravity says, among other things, that apples fall--first time, every time. It does not say why. Theories offer coherent and verified explanations for the natural phenomena that are summarized by laws. Newton's theory of Universal Gravitation explained the workings of the law of gravity by explaining how and why apples fall. Anyone who appears to believe that the theory is some sort of "wannabe law" is giving more evidence of scientific unsophistication. Jeepien

"Clearly"? Don't say, mister? What in the world (and heavens alike) does Smoot's work or ID loonies have to do with the definition hierarchy, or with whether GPS proves the Einstein's relativity or not? You suffer from a serious bias when it comes to the upholding of definition hierarchy in science. For instance, you say "the theories work to the last available decimal place" but then, according to your own criterion, the Einstein's GR is not even a theory (a hypothesis, perhaps?) since it obviously does not work practically AT ALL as the current model based on GR cannot account for 98% of the mass of the Universe. Wow, how's that for the "last available digit"! Your distorted view on truth is boundless indeed -- look at your own ill logics: first you say that physical laws do not explain but only describe. Then you say that laws are actually parts of theories that do explain. Unless you deny completely (which you cannot, you just said one is a part of the other!) that laws serve the purpose of explaining, then by all means man, do show us those laws that are incorporated in the Einstein's theories and that DO WORK IN 100% OF CASES AND 100% OF TIME because Mr. Einstein (and his trolls) claimed universality of his ideas so at least SOME PARTS OF HIS THEORIES MUST BE SUPPORTED BY SOME LAWS! Relativistic physicists have indeed conveniently assumed that NO DATA are needed in order for a theory to be proven. "If the data don't fit the theory, change the data" -- said their guru Einstein. Amazing, how far some will go in order to get their undeserved fame and that damn funding money (for His followers). Funny to learn that Einstein’s trolls now are prepared to get into even deeper mud however: by reversing the order of definition hierarchy in science. Do the mankind a big favour -- go back to sleep. And take your Mickey Mouse theories with you. Uknewthat 17:35, 11 October 2006 (UTC)

I am sorry, but both Jeepien and Uknewthat are confused. According to the most common intrepretation of scitific theory, there is no qualitative difference between what is named a "law" and a "theory". There is a historical one: discoveries made befor 1800 seems more often to get the name "law", the ones that are of a later date get the (more correct) name "theory". There is no point where a "theory" gets promoted to a "law", there is no committe that decides which is what. For more in depth knowledge, read the articles in Wikipedia about scientific theory, or read the book by Chalmers.Mossig 17:54, 11 October 2006 (UTC)

It's been a week since I protected this page, and I was wondering whether enough progess had been made for me to unprotect. SlimVirgin ^(talk) 19:59, 12 October 2006 (UTC)

EVERYONE: Please note that, in an agreement with SlimVirgin, I have only added a paragraph to the GPS page, without doing any edits to the rest of the page. The added paragraph is based in part on the discussion that can be found here, on the GPS page. I did not know how to properly reference Mr. Deines's paper, so I just added this reference as text; can someone please make it look nice like the rest of the reference list? Thanks. Uknewthat 01:39, 15 October 2006 (UTC)

Since SlimVirgin lied (as expected) about the "deal", I requested arbitration at http://en.wikipedia.org/wiki/Wikipedia:Requests_for_arbitration . Uknewthat 13:10, 19 October 2006 (UTC)

Reverted October 29, 2005 because WP:EL#Links normally to be avoided "6. Links to bookstore sites. Instead, use the "ISBN" linking format, giving an opportunity to search a wide variety of free and non-free book sources." Also, I believe the discussion above states that you are misrepresenting Alfred Leick's book. --Dual Freq 14:55, 29 October 2006 (UTC)

Uknewthat completely misrepresents Leick's material. The specific misrepresentation is this quote: "Likewise, in relative positioning, most of the relativistic effects cancel or become negligible." Leick's book is on GPS surveying. When GPS is used in surveying one stationary receiver is situated at a well-known point and another receiver is placed over the point being surveyed. Since the base station knows exactly where it is and where the GPS satellites are telling it where it is, it knows what corrections need to be made in order to tell the rover exactly where it is. This is the "relative positioning" that Leick mentions. It is capable of removing nearly all of the error factors in GPS. It's what allowed people to get centimeter accuracy even when Selective Availability was turned on. Uknewthat uses this quote because he thinks it is saying that relativity does not need to be applied in GPS as a system, when actually, Leick addresses relativity directly in that same book on page 75: "The atomic clocks in the satellites are affected by both special relativity (the satellite’s velocity) and general relativity (the difference in the gravitational potential at the satellite’s position relative to the potential at the earth’s surface)." - Justin 19:47, 29 October 2006 (UTC)

Einstein's groupies completely misrepresent Leick's material. There is nothing special about relative surveying, contrary to what they are trying to portray. It is completely irrelevant to this discussion what GPS surveying is. On the other hand: Leick does not say that the effect of relativity on atomic clocks on board satellites is crucial (critical) for the GPS operation. Furthermore, look at the order of magnitude of such effects, to grasp why it is irrelevant to the GPS. Finally, if it were critical, corrections to account for such an effect would have been applied from the day one in the GPS. Deines teaches us that this was not the case prior to 1990-ies. Since the adding of apples to a basket of oranges generally will not affect the oranges, feel free to remove the apples. Uknewthat 17:13, 30 October 2006 (UTC)

What is an "Einstein groupie"? - Justin 17:59, 30 October 2006 (UTC)

The mirror will tell you. Uknewthat 16:15, 1 November 2006 (UTC)

Deines does not say that at all. You seems to continously misrepresent yor sources. Have you at all read the articles, and not only the abstracts? See for example: Deines, "Uncompensated relativity effects for a ground-based GPSA receiver", Position Location and Navigation Symposium, 1992. Record. '500 Years After Columbus - Navigation Challenges of Tomorrow'. IEEE PLANS '92. Your grasp of the workings of the GPS system seems also to be a bit fuzzy, especially when you say that relative positioning, as used in surveying, and absolute, as used in navigation, does not differ. Which is plain worng, and should be evident from reading Leicks book. Mossig 19:56, 30 October 2006 (UTC)

"You seems"(sic) like you should start with some easier reading, such as Grammar, prior to moving on to scientific papers... Uknewthat 16:15, 1 November 2006 (UTC)

I asked for advice about this situation at the physics Wikiproject, and was advised that anything that cannot be backed by this review — Ashby, Neil. "Relativity in the Global Positioning System" — can probably be deleted on sight. Are people in agreement with that? SlimVirgin ^(talk) 20:12, 30 October 2006 (UTC)

What an arrogant individual you are (besides being a proven liar; see above). Let’s see, "the physics Wikiproject" is competent in GPS – how? You (anonymous) being advised by someone (also anonymous) gives legitimacy to your OBVIOUS violation of Wiki regulations – how? "Advice" by anonymous visitors to anonymous administrators are regulated NOWHERE in the Wiki regulations, precisely in order to save the Wiki from VANDALS like you. Hence Wiki has so many useful regulations, EXCEPT the one you just made up. And so he shot himself in the foot… So, you have just created a whole new IMAGINARY (unregulated) world for yourself and the "people" (more anonymous ones…) that you farcically are asking if they "agree" with you… Admit it – you are just as ignorant as the rest of your "people" when it comes to Einstein's relativity and GPS (otherwise you would not be invoking “advice” from Men in Black), even with help from MOSSAD directed by a rapist-President… What a funny bunch you and your ignorant “people” are. Oh, man, am I having a good laugh here. Pretty soon, this same arrogance with which you so preposterously defend the indefensible theory of a lunatic patent clerk will result in your losing the Capitol Hill, the White House, then the US, then the West, and then… will there be a change of continent once again... Uknewthat 16:15, 1 November 2006 (UTC)

After just a quick look I agree. Which is the physics wiki, BTW? Seems interesting. Mossig 20:18, 30 October 2006 (UTC)

This one agrees WITHOUT EVEN KNOWING what it is that he agrees with... Monty Python at its best... Uknewthat 16:15, 1 November 2006 (UTC)

It's at Wikipedia:WikiProject Physics. SlimVirgin ^(talk) 20:39, 30 October 2006 (UTC)

I also support deleting anything on sight which can't be backed in that paper. That article has been cited in discussions here numerous times in the past weeks. It seems to be the most authoritative summary of relativity in GPS. The book on GPS surveying by Leick (the same "classical book" referred to by Uknewthat) cites that exact article (pg 75). However, Uknewthat has previously dismissed it without proof or explanation: "Ashby has an agenda". - Justin 20:34, 30 October 2006 (UTC)

Oh, man, this one even supports it, too. No matter that Wiki regulations have no regulation that allows them to take justice in their own hands. I so hope John Cleese will read this (some day). I am positive he will exclaim: I KNEW THAT! Uknewthat 16:15, 1 November 2006 (UTC)

Okay thanks, guys, that's a big help. SlimVirgin ^(talk) 20:39, 30 October 2006 (UTC)

And this one, like, encouraged by all the support he received (poor Wiki -- what became of it), prepares to proclaim his sovereignty over the “GPSland” on the planet Wiki. Turn on that Warp, and do beam yourself up... Well, let me tell you son, you exhibit some unbelievable arrogance. But still, it cannot save you (or your "people") from having to offer (here and now) an actual and understandable EXPLANATION on what Time is, which according to the worshiped patent clerk A.Einstein can "stretch" or "shrink", resulting in a whole slew of magical terms and concepts all of which remain unproven after one hundred years… Then, while at it, do explain to us why you and your “people” are so persistent in virtual BURNING OF A SCIENTIFIC REFERENCE? Bad dreams? Uknewthat 16:15, 1 November 2006 (UTC)

Plain English

This article seems a good technical explanation. Wikipedia though is an encyclopedia for everyone and the article needs, in addition, a plain English overview explanation for intelligent and interested entry level newcomers. Unfortuanately I dont have the knowledge to write this. Lumos3 09:43, 25 September 2006 (UTC)

Number of Satellites

I was going to revert the 29 sats back to 24 as well until I checked the satellite almanac at USCG navcen[4]. Health code 000 means the satellite is healthy and I count 29 satellites. Am I counting wrong or is there something that says 24 somewhere else? --Dual Freq 23:49, 26 April 2006 (UTC)

Number of sats question again - I'm counting 29 active satellites, and 1 inactive with health code 063 (PRN 15).[5] [6] See also this warning about more than 30 PRNs indicates a 31st will be launched soon. I changed the page to 24 and noted it is the min required. Active PRNs change often enough it doesn't make sense to maintain a current number in orbit. Dual Freq 12:12, 1 November 2006 (UTC)

Seems like the number should be the number of satellites, not the minimum that they want to keep active at one time. The article / paragraph is about the GPS, not a position system. Davandron | Talk 14:16, 1 November 2006 (UTC)

Miniature Atomic Clocks

There is a presentation from the Sept 2006 GPS meeting which discusses how new miniature atomics could improve GPS: PPT of Presentation. Think it might be good to integrate into the article, especially in a future improvements section?Davandron | Talk 19:19, 13 November 2006 (UTC)

What is the relationship between GPS and WGS84?

The WGS84 article claims that "WGS 84 ... is currently the reference system being used by the Global Positioning System."

Perhaps this GPS article should mention WGS 84.

If the D.O.D. wanted to convert the entire GPS system to some reference system *other* than WGS84, would that require sending up a completely new constellation, or is it "merely" a matter of reprogramming the ground recievers?

--DavidCary 05:29, 21 October 2005 (UTC)

According to what I know of the Global Positioning System, the locations of the satellites are set according to some fixed reference point in the WGS-84 system. This (current) location of the satellite as well as the orbital information is sent to the satellite from ground stations. Along with the time code, each satellite broadcasts this position information. The GPS receiver (GPSr) uses this information to synchronize its clock and update its internal database of satellite location and orbital information. Everything is calibrated according to WGS-84, but the GPSr could perform its calculations and render the results in some other Earth model. Val42 15:12, 21 October 2005 (UTC)

To say it shortly: A coordinate is useless as long as you don't have a reference system. Maps have a reference system, too, the most common is WGS84. All GPS-coordinates are natively WGS84-coodinates. If you have another (like ED50), you cannot plot your coordinate directly in the map, but you have to calculate the ED50-coordinate (It will make a difference of a few meters, but in some areas it can become up to 200 meters). --Lowfly 09:08, 2 December 2006 (UTC)

Selective Availablility

Selective availability has not been discontinued - as the GPS entry has been re-edited to say. It has been set to zero, which, while effectively the same thing to the average user, has an obviously much different meaning. 2SOPS did not discontinue SA (like its some kind of an iPod or something). Would it make sense that they would take that capability out of the system when simply setting it to zero produces the same effect? The article should reflect the correct information. the_other_steve_jobs 15:51 7 Nov 2006 (UTC)

As you can see by the Presidential Directive, what i am saying is exactly what has happened. "The decision to discontinue SA is coupled with our continuing efforts to upgrade the military utility of our systems that use GPS, and is supported by threat assessments which conclude ***that setting SA to zero*** at this time would have minimal impact on national security." That should be reflected in the article. Based upon the Presidential Statement and the fact that there is no logical argument for why going thru the hassle of removing the capability from the system, and that it would actually take time and cost money taking out a capability from the system - i think its clear that the article should read that SA is now set to zero. the_other_steve_jobs 15:56 7 Nov 2006 (UTC)

The Presidential Directive uses the phrase "discontinue SA" (or some variant of that) five times, and "discontinuing the use of SA" once. It doesn't imply that the capability has been removed, just that its use has been discontinued. "Setting SA to zero" doesn't make any sense to me. "Discontinue SA" is much clearer. Pfalstad 17:06, 7 November 2006 (UTC)

The point of the PD was to obfuscate. It says both "discontinued" and "set to zero". The fact is: it is _actually_ set to zero, and not discontinued. If something is discontinued, that means its gone, never to return. But that is not the case, SA is not gone. Setting SA to Zero vs. Discontinue is the difference between the volume knob on your car stereo being turned all the way down vs. your car stereo unplugged and sitting on a shelf. SA has not been unplugged. SA is, in fact, turned on right now. I just saw the screen this morning. The amount of error put into the NAV uploads at this time is "0" Circular Probable Error. This means that the system is processing SA, its just that the error is "set to zero". Hopefully, its obvious and clear that that distinction is quite important: If its not unplugged - the knob can be turned. the_other_steve_jobs 19:45 7 Nov 2006 (UTC)

I don't think "discontinued" implies it's gone forever. For the history section, I think we should say "discontinued" or "turned off". "Discontinued" because that's what the PD says. (Do you have a source for the claim that obfuscation was the goal?) "Turned off" because that clearly implies that it is now off but could be turned on. The details of how it was turned off are not of historical interest. It doesn't matter if SA is still bring processed but the result multiplied by zero. The result is still the same as if it were not being processed. Saying SA was "set to zero" is too much technical detail, esp. for the history section.

For the selective availability section, if you want to supply the exact details of how SA was turned off, be my guest. You clearly know what you're talking about. But don't just say that "SA was set to zero", because it's not clear what that means. Try to make this article as accessible as possible.. [7] Pfalstad 20:38, 7 November 2006 (UTC)

Not to sound critical.. but the fact that this is confusing at all proves my point that there has been obfuscation around the whole issue... the PD used two different terms that could lead someone to come up with different understanding of what exactly happened. That's the definition of obfuscation. The technical _fact_ is that SA is neither turned off nor is it discontinued. Selective Availability is currently turned on, and it is being processed each day across the quad from me. "Discontinued", to me, implies much more permanance than it does for you. For example, i've tried to buy a discontinued iPod mini, and it was a bitch because they don't make them any more. This is different than "being turned down to zero", a la a volume knob. That is to say, its much harder to get a "discontinued" iPod than it is to turn the volume up on an iPod which is plugged in and turned on and right in front of me. For the history section - i would simply say "state the facts" and add some dialogue to make it abundantly clear. For example, something to the effect of

"As of 2000, a PD states that the US is no longer putting intentional errors into the GPS signal. All public users are able to process GPS signals without any induced error. However, the SA capability to insert error remains completely in tact and has not been removed."

I think its also clear that a section needs to be put in about SA to technically discuss what SA is and how it works, as well as its current status... that SA is actually *on* and that its error radius is set to 0m, and that it can be adjusted at a moment's notice, etc. I think that a history section is a bad place to discuss this - you're right. But i don't think that its too hard to understand what being "turned down to zero" means... you're car stereo has a mute button, and iPods have a volume adjustment that can be turned to zero - and SA is the "volume knob" for error. the_other_steve_jobs 21:45 7 Nov 2006 (UTC)

It's not hard to understand if you explain it, sure. Which you now have done. Pfalstad 22:51, 7 November 2006 (UTC)

btw: i just remembered where i first saw the term "SA set to zero". it was on this page - [8] in the Constellation Status message. "4. Selective Availablility (SA) levels set to zero. On May 2, 2000 at 0400 UT, SA levels were set to zero. For more details, check the Interagency GPS Executive Board (IGEB) web site at http://www.igeb.gov." I should have referenced that at the extreme beginning of this whole change. My bad. the_other_steve_jobs 02:10 10 Dec 2006 (UTC)

Bicycle Application

The bicycle application section added by 222.2.104.196 appears to be original research and needs sources. Without additional info, I'm not sure how the bicycle application is any different than navigating in an automobile. Davandron | Talk 01:05, 1 December 2006 (UTC)

Main Article Length

The main article is now 64k in size, double the recommended size, so this maybe a good time for a split. It looks like there is enough information to break away the Applications section into its own article. What does everyone think? - Davandron | Talk 14:24, 1 December 2006 (UTC)

The Applications section is going to continue to grow. I would support a separate article for Applications of GPS at this stage. We should probably spin off a few of the specific applications into separate articles of their own as well. I'm thinking that GPS Surveying and Location Based Services could be expanded into individual articles. - Justin 16:15, 1 December 2006 (UTC)

I'm working on splitting it right now, and leaving short but usable prose in its place. One thing that is clear is the technical discussion currently in the application should migrate elsewhere in the main article. The sections I'm thinking of right now are L1 & L2 comparisons for surveying and how "GPS time" is composed. For the moment, they are moved into the split but that will be fixed by myself or others.

In addition to the split, I'm moving the (now stubby) application section further down. Since the wiki is an encyclopedia, my understanding is the article should be arranged "What it is, How it works, When it came to be, How its used."

BTW, it looks like this split will lead to a sizeable reduction; approximately 20% - Davandron | Talk 14:55, 7 December 2006 (UTC)

Please don't split Applications from the GPS article. I think the article can be shorteded significantly with a little careful editing, which I already started. If there must be be a split, I think it would be better if the Technical section was set on its own, not Applications, for two reasons. First, the article has been flagged already as being too technical, and splitting the more technical part off on it's own would help with that. And second, the Technical section is longer than Applications, so it splits the article more evenly in length. --Michaelfavor 15:41, 7 December 2006 (UTC)

Michael, I'd like to hear your arguements on why the applications section should not be split. I know you've been working on length-edits as well, which is great. Unfortunately, even with a full split on applications the article is still way above the recommended limit.

I wish you had added your input earlier. At this time we've got 2 in favor and 1 opposing an applications split. I'm going to restore the split because that will generate more discussion, and because a period for comment was given prior to the split occuring. - Davandron | Talk 18:49, 7 December 2006 (UTC)

Davandron, I offered what I thought were two good arguments above. Below, Reswobslc suggests that more people are interested in GPS Receivers (Applications) than are interested in the technical details of how the system works. I happen to think both topics are interesting, but I see his point. It seems reasonable to me that if any part of the article is going to be split off, it should be the more detailed information, not the more popular Applications section. At the very least, I would say that makes the vote tied 2-2 in favor of not removing the Applications section. As I mentioned above, the article has been flagged as being too technical. If the Applications section is removed, it tips that balance even further in the wrong direction.

I appologize for not responding to your proposal sooner, but frankly, there had been a lot of discussion on this page recently that I had stopped following. It is also customary to add new topics at the bottom of the page. Now that I am aware of your suggestion, I don't think my previous lack of a reply should be held against me. At no point did you say, "I'm going to make a major change to this article in X number of days unless anybody objects." If you had, I think it's likely that somebody would have objected. In my own way, I'm taking the opportunity to object now. Although the article is larger than recommended, it is a more complicated topic than most. I believe the article is too long mainly due to a lack of focus, redundant information, extraneous and off-topic details. As you noticed by the article history and our edit conflict this morning, I was in the middle of trimming out some of that fluff when you made your big move. My position is that although the article is too big, it can get a lot smaller without breaking it up, and if that is possible, it is better not to break it up. First of all, I ask you to give me a week or two to edit for length. If you still feel the article is too long, maybe we can compromise and separate the Technical Description section rather than the Applications section. In the meantime, since is is clear that we do not have a consensus, I humbly request that you leave the article in once piece until a few more people have a chance to offer their opinions. Thanks for your consideration. --Michaelfavor 20:08, 7 December 2006 (UTC)

OK, lets try to edit it down without the split. The article was shortened from 64kbytes to 50kbytes via the split; if we can accomplish 75% of the benefit without a split I'd say its worthwhile. - Davandron | Talk 20:21, 7 December 2006 (UTC)

Thanks, Davandron, that sounds reasonable to me. If it doesn't work out, I'm open to a different solution down the road. --Michaelfavor 20:32, 7 December 2006 (UTC)

The page is now at 52kbytes. --Michaelfavor 02:45, 9 December 2006 (UTC)

I recently had the "good fortune" to be editing this article on very old machine with little memory, running on a dialup connection; it was a pain in the ass. While this size is ok for viewing, some contributors are probably going to face the same difficulties I did and I can understand why the 32 kbyte size is suggested. Even at 52kb, I think we as editors need to explore how to refractor the article so that is manageable to all users. —Preceding unsigned comment added by Davandron (talk • contribs) 16:18, 12 December 2006

How it works - availability of at least four satellites

Hi, basically there should be at least four satellites on the horizon. But I heard in special cases the positions of the satellites can be changed be the Military to provide a better coverage of selected areas, but I never found a reference for this. Does someone know more? --Lowfly 09:17, 2 December 2006 (UTC)

I know quite a bit - but only because of my job, not because i'm really smart. The satellites are in more or less fixed in their positions per the way the constellation must be laid out. There are 6 orbital planes, and 4 nominal slots per plane. Obviously, when a bird dies, we have the ability to move a new bird into a slot, and we have a number of birds sitting nearby a current bird ready to take over their slot when they get too old and die. Also, routinely, the birds are very gently scooted if their orbit has moved outside of a nominal constraint - but its not by a lot... its just a scootch. Bear in mind, however, the there is only so much fuel on board each bird. If you used up fuel on the bird to move the bird around, you'd end up "killing" the bird very fast. So to directly answer your question - no - massive moves of birds for a particular coverage area are not done. Its easier for the military to work around GPS, instead of the other way around. They can simulate the constellation and look ahead and see when coverage is going to be optimal or sub-optimal. Bear in mind that at its worst, GPS can still put a bomb on any reasonable target without much issue.the_other_steve_jobs 02:20 10 Dec 2006 (UTC)

Older discussion topics moved to Archive 1

I moved a lot of older discussion topics to /Archive 1 as suggested by WP:ARCHIVE --Michaelfavor 16:30, 7 December 2006 (UTC)

A small sidebar: I remain concerned about the archiving, which is only a "technical how to" in the guidelines, and make the simple proposal that all moves err on the side of caution; waiting until its definately too big and the things being moved are definately old. - Davandron | Talk 17:52, 13 December 2006 (UTC)

Michaelfavor, please do not edit my comments, even if you feel it would make more sense. The talk page guidelines (which you recently linked) discourages editing of anyone's comments, including your own, and marks it as unacceptable behavior. - Davandron | Talk 18:56, 14 December 2006 (UTC)

I appologize if this upset you, that was not my intention. I did not remove any of your words, or mis-represent your meaning, only refactored your comment slightly. Since this seems somewhat off-topic for this page, I have posted a full reply at User_talk:Michaelfavor#Editing of comments. --Michaelfavor 20:43, 15 December 2006 (UTC)

I also understand your lingering concerns. If our positions were reversed, I would probably have concerns, too. I will try to answer those as time permits. For now, I can only reassure you that my goal is to continually improve the article in a thoughtful, intelligent way. It seems to me that most issues that appear on the talk page have a natural life-cycle, eventually they are addressed in the article and/or reach some other natural final conclusion. It seems reasonable to me to archive inactive topics somewhere on the order of once a year, possibly as often as quarterly depending on the level of traffic, but probably not more often than that except in special cases. When the size of the talk page reaches the size limit of an article, I think it's time to start looking at archiving. The amount I moved to the first archive was roughly twice the size of the article. I ask you to trust me on this, and don't worry too much about something that hasn't happened yet. There are plenty of actual defects in currently existing articles that are more worthy of your time and attention. --Michaelfavor 16:06, 14 December 2006 (UTC)

After reviewing the archive, I found a couple of small topics relating to the currently ongoing discussion of the overall structure of the article, and a couple of small topics with recent comments which have not been addressed yet in the article. I have moved these back to the main talk page. Archive 1 is about 125k, and this talk page is now about 33k. --Michaelfavor 16:45, 14 December 2006 (UTC)

GPS vs. GNSS

This article is too US specific, covering generic GNSS functionality under the more specific GPS term. To make the article more international and generic, GNSS items should be in a GNSS article, and the GPS article should focus on the unique features of GPS that distinguish it from other GNSS. The applications split was a good first step down this road, and I was going to propose changing "GPS Applications" to "GNSS Applications", before it was reverted. (See the GNSS article for links establishing GNSS as the correct generic term.) Dhaluza 05:05, 8 December 2006 (UTC)

It looks to me like the GNSS article is actually little more than a stub, and should probably be merged with satellite navigation systems. It's easy to imagine how anyone who searched for "GNSS" might be dissapointed with the result. I think a redirect to satellite navigation systems would be better. --Michaelfavor 16:29, 8 December 2006 (UTC)

No, GNSS is the accepted generic term for GPS and its peers. GPS is essentially a brand name of GNSS. The taxonomy is as follows:

• SNS
  • Obsolete systems
  • GNSS
    • GPS
    • Glonass
    • Galileo, etc....

It is OK to keep SNS as a separate overview article that covers the history up to GPS. All the generic content from the GPS article, such as applications, belongs in the GNSS article, since it is similar for Glonass, Galileo, etc. The GPS article should contain GPS specific information like GPS program history, and technical differences like SA, C/A, P(Y) etc.

Until now, GPS has been the dominant GNSS, so there is some conflation of the two, kind of like the US brand name "Kleenex" being used instead of the generic term tissue. This needs to be corrected since it is not in line with Wikipedia MoS formality requirements, especially now that Galileo is scheduled to enter service in 2008.

See also: Talk:Satellite navigation system —The preceding unsigned comment was added by 70.198.253.77 (talk) 18:02, 8 December 2006 (UTC).

Are you saying GPS should be renamed/replaced with GNSS? If so, I don't agree with that. GPS is a specific system and implementation. The applications section could definately move, as thats related more to GNSS than GPS, but the technical content is specific to the US DoD's NAVSTAR / GPS. - Davandron | Talk 20:17, 8 December 2006 (UTC)

GPS should stay, but should focus on GPS specific topics. GNSS general topics belong together. Dhaluza 23:59, 8 December 2006 (UTC)

Applications

As you mentioned a lot of the apps section is fluff / redundant / "me too!" It seems that the GPS boils down to three functions/services usable by applications, so how about this structure for the reformated content:

1. Location Determination <- what's a better way of saying this?
   1. Navigation and Guidance (covers navigating for all topics; sentences not subsections. Conceice is the goal; no need for redundant "me toos")
   2. Surveying & Mapping (Quick blurb about how gps is used for surveying and mapping)
2. Time Transfer (covers use of GPS to synchronize regardless of distance)
3. Nuclear Detection (short and sweet blurb)

Yes, the article is long, and there are some redundancies. However, all this editing is getting out of control, and is very hard to follow. Also we are losing content, and this is no good. For example, the whole Precise time reference section seems to have been deleted, and this is no good. It should have been moved somewhere, not erased. I'm trying to go through all the revisions, but there have been over 250 in the last month. This makes it very tedious to check on what has changed. Dhaluza 00:06, 9 December 2006 (UTC)

Dhaluzu, I would like to reassure you that I have tried to be careful not to lose any important content. The 'precision time reference' section you mentioned is definitely not missing, it's still in the 'applications' section, under 'other'. Perhaps I should have used the sandbox method to reduce the number of edits, but it seems to me that due to the limitations of the Wikipedia 'version/difference' system, that would actually make it harder for people to check my work. Also, it seems to me that Wikipedia lets you bundle together as many changes as you like. If you want to lump together all of my edits, or even compare the version you are familiar with from last month with the current version, I think Wikipedia makes it pretty easy for you to do that. My goal today was not offend anyone, only to try to increase the signal-to-noise ratio of the article in the most transparent way possible. It occurs that although I am responsible for a large number of edits, your experience of 'missing' content may have actually been due to an edit by someone other than me, but since you didn't mention any particular version, it's hard to tell. Best regards, --Michaelfavor 00:57, 9 December 2006 (UTC)

Michaelfavor, the problem is you are both moving and changing content, and this completely breaks the version comparison. Most of the changes you are making are helpful, but it is difficult to check your work, and the work of others that has been mixed in. Dhaluza 01:33, 9 December 2006 (UTC)

(original comment withdrawn) I incorrectly stating the timing section had been removed; it had been relocated, and I missed it with all the edits. My apologies to Michaelfavor and my thanks to TiCPU for the correction - Davandron | Talk 16:12, 12 December 2006 (UTC)

I would agree that the Applications section should be shorted and the more fluffy bits should be removed. All of those thigns smack of poorly produced Discovery Channel blurbs to fill time in a 60 minute special. I will keep out of the editing seeing as how it appears that there are already too many cooks. I will, however, put in my technical 2 cents here in the Talk section when i see something that needs to be corrected from the space and control segments (user segment being the 3rd and final other segment of GPS). I would assume, without knowing full names here, that i most likely have the best vantage point to those segments, unless there's someone else that can throw paper airplanes and have them land in a 2 SOPS operator's cubicle that's doing editing around here. I think that if this is going to be a "GPS" article (vs. a GNNS article) - which it should be - i think it would be pretty interesting to put in data about the consetellation - like status and other intersting NANUs. ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt is a great page and i think that kind of constellation details wouldn't hurt to replace the "you can put a GPS on your bike!" type fluff. That's just my opinion, and like i said, i see there are a lot of guys hacking on the article, so i'll stay well away. The Other Steve Jobs 2040 9 Dec 2006 (MST)

Older topics have been archived

Please start new topics at the bottom of the page. Older discussion topics have been moved to /Archive 1.

Topics sorted by date

I propose to sort the topics on this page by the date the topic was started. I hope no one will be offended by this gentle refactoring, and if so, this entry should provide a convenient revert point. I'll move just one topic at a time, to try to make the sort as transparent as possible in the page history.

Adding new topics to the bottom of the page will make it somewhat easier to archive in the future, if necessary. --Michaelfavor 14:58, 13 December 2006 (UTC)

If you propose something, don't you think its appriopriate to give time for a reply? I've reverted so that that discussion can take place.

Some questions and thoughts.

• To my mind, if we are archiving off old topics, it makes more sense and is a better use of page-space to have new topics be added to the top with old topics rolling off the bottom. Besides the "+" button functionality, is there any reason to have new topics be appended?
• (addressed in original post, sorry!) As for how they are chronologically organized, is it by first post or most recent post? I assume its by first post date, as recent post doesn't make much sense to me (since it will quickly "breakdown"). But what is the advantage?
• What is the indentifier for something moving to archive? The relativity war here has continued for a long time and might get started again if the lengthy discussion is missing (due to it being archived since it has no new edits).

- Davandron | Talk 15:36, 13 December 2006 (UTC)

Davandron, Wikipedia guidelines suggest, in bold, start new topics at the bottom of the page. This is an established Wikipedia convention, lets not reinvent the wheel here. Likewise, the Wikipedia guidelines for archiving talk pages suggest answers to your other questions. Briefly, the plan is to wait until the page is obviously bloated, and not to move topics that are actively being discussed, which seems reasonable to me. Regarding the other debate you mentioned, as Grandad would have said, let's let sleeping dogs lay. If it does flare up, I'm prepared to argue that this is not the proper forum for that discussion. --Michaelfavor 16:36, 13 December 2006 (UTC)

Thank you for the link to the guideline regarding ammending discussions to the end. It seems we could all benefit from reviewing that once more.

Since that addresses my main point of discussion, I will not oppose the re-org if it helps in the archiving. I do request it be done without creating a flood in the history. I don't mean it as a personal attack but the two pages of consecutive edits on the main article is very annoying. Please use the preview button, review your work, then hit save. (I also just learned there is a {{inuse}} tag, explained here).

Davandron, thanks for your thoughtful reconsideration of this and other issues over the last few days. Both of your appologies are accepted without malice. And I'm sorry if the briefness of my comments caused any concerns. Sometimes I have a tendency to want to skip over the explanation of detailed steps, and jump straight to the conclusion. This was a constant complaint of my first Algebra teacher ("show your work!"), and I'm afraid I sometimes fall prey to the same habit today. I actually intended my opening phrase "I propose to sort..." in the sense that I wanted to imply "...beginning immediately after I save this comment, and continuing indefinitely into the future. If a new topic is started at the top of the page in the future, I may move it to the bottom of the page, in accordance with the wikipedia talk page guidelines and refactoring policy, and possibly without further comment other than an edit summary." I used the word "propose" because I didn't want to state flatly that I will do it, in the sense of a promise to do it, but if I happen to be reading this page and something strikes me as out of order, I may change it. My comment was intended to be, as briefly as possible, my explanation in advance. It probably would have been better if I had cited both of the relevant guidelines in the very beginning. --Michaelfavor 16:06, 14 December 2006 (UTC)

Rewrite of Techniques to improve accuracy

I've re-written the section labeled "Techniques to improve accuracy" in order to improve that section and the whole article. A major goal was to convert the list to prose (per guidelines), and I ended up also migrating specific examples which had their own article into a link-through approach.

The sections on Precise Monitoring are specific to GPS so they were left mostly intact. I didn't re-write the RPK section since I wasn't familiar enough with it. Can someone help there.

My edits left two things on the cutting floor, which need to find a home in the wikipedia:

1. Wide Area GPS Enhancement (WAGE) is an attempt to improve GPS accuracy by providing more accurate satellite clock and ephemeris (orbital) data to specially-equipped receivers.
2. Exploitation of DGPS for Guidance Enhancement (EDGE) is an effort to integrate DGPS into precision guided munitions such as the Joint Direct Attack Munition (JDAM).

Please help these orphan snippets by either linking them into the GNSS Augmentation article. - Davandron | Talk 23:33, 14 December 2006 (UTC)

Modernization Section to be added

I'd like to add a modernization section which explains the new signals being added to GPS over the next few years. I'm going to develop the work in a personal sandbox and present it for integration in the future. If you would like to collaborate prior to integration, just use my talk page to leave me a note (i'm completely open to collaborating).

I'll be making the new section in a sandbox in part because I feel I should take a break from editing GPS to allow the community some time to review my recent copy-edits and generate feedback (if its needed). Thanks everyone - Davandron | Talk 05:42, 16 December 2006 (UTC)

New entry for gps receiver

I am going to start a separate entry for GPS Receivers. If anyone sees a link to _GPS_ receiver, please replace it with _GPS reciever_ --Omnicog 20:46, 12 September 2006 (UTC)

What on earth is the "please replace ..." request above - it reads as nonsense. I have converted GPS receiver back to a redirect. I think there should be consensus here before a fork is started. -- RHaworth 11:26, 13 September 2006 (UTC)

What fork? The GPS is a system of satellites, the GPS Reciever is a electronic device. You erased the entire entry? --Omnicog 15:47, 26 September 2006 (UTC)

I think GPS receiver could be a stand alone article, there is probably enough to talk about. —Preceding unsigned comment added by Davandron (talk • contribs)

I have always believed GPS receiver should be a standalone article. A person who has never heard of "a GPS" wants to first learn about that gadget he saw in his friend's fishing boat, not about coarse acquisition codes and what frequency WAAS uses. Further, GPS should be a disambiguation page that lists GPS receiver and Global Positioning System as its first two entries, instead of being a redirect to Global Positioning System. Reswobslc 21:29, 16 December 2006 (UTC)

The GPS redirect page

Hello,

I would like to propose that the page named GPS, which is currently a redirect to Global Positioning System, become the disambiguation page. The main reason I suggest is that a GPS receiver is frequently referred to as "a GPS", and the person looking up GPS is highly likely to want to learn about a GPS receiver rather than the actual satellite system that runs it. I believe that as many or more people looking up "GPS" want to know what "a GPS" (receiver) is as would ever be interested in C/A codes and ionospheric effects.

Such a page would start out saying something like "GPS stands for Global Positioning System."

• Global Positioning System, a system of navigation satellites
• GPS receiver, a handheld or vehicle-mounted navigation system

Then it would go on to list all of the non-navigation related things GPS can stand for. Reswobslc 02:19, 13 October 2006 (UTC)

IMHO, if one turns to an encyclopedia, they should expect a discussion of the proper noun first, with an "also see, ..." at the top for related but slightly dissimilar topics. I understand where you are coming from, and if GPS Receiver can stand on its own as a page then there should be a "also see" at the top, but Global Position System is GPS, where as GPS Receiver is not the same as "a gps." Its not a matter of disambiguation. Davandron | Talk 20:54, 7 December 2006 (UTC)

In colloquial language, "a GPS" is a GPS receiver. That's just how it is, as in "Honey, can you bring me my GPS?", or my car has GPS. The job of a disambiguation or redirect page is to help people find what they're most likely looking for, and not to pester people with technicalities. While Wikipedia's audience includes both lay people and engineers, there are a whole lot more lay people out there that think of GPS in terms of what's in their car or boat, and not what's in the sky, and that's why GPS needs to be a disambiguation page that includes GPS receiver. See the comment above, under the heading Plain English, for a prime example of what I mean.Reswobslc 21:36, 16 December 2006 (UTC)

Is GPShacks linkspam?

With this edit on 23:08, 19 December 2006, anonymous user 216.93.53.114 added a link near the top of the external links list to the website "gpshacks". The site has minimal GPS content, most of it appearing within the last three months. The site is free but contains numerous Google-ads. Further, the user has a history of link-spamming.

I have removed the link, believing it to be link spam, please discuss if you feel it should be restored. - Davandron | Talk 23:28, 19 December 2006 (UTC)

It looks a lot like linkspam. That IP address has inserted material into the External links section of a good number of pages and has been warned repeatedly because of it. The page itself looks like a blog with a lot of Google Adsense. I'm comfortable with removing it. - Justin (Authalic) 00:32, 20 December 2006 (UTC)

Hidden notice in article concerning links

I have added the following hidden notice, just below the External Links header. Since its encased in comment tags, it will only be visible when a person is editing near that section. The notice reads as,

 <!--================================================================-->
 <!--   Please follow wikipedia policy on external links,            -->
 <!--       which can be found on the page WP:EL                     -->
 <!--If you have a link that you want added please use the talk page -->
 <!-- to explain why you feel it should be included in the article.  -->
 <!-- Doing so will let other editors understand what you are doing  -->
 <!-- and will prevent misunderstandings from turning into reverts.  -->
 <!--================================================================-->

Hopefully, this will help mitigate misunderstandings regarding external links. - Davandron | Talk 19:44, 20 December 2006 (UTC)

Featured Article?

Theonlysilentbob tagged the article as a Featured Article Candidate (woohoo!) but, as Dhaluza commented, now probably isn't the best time for peer reviews (since there is on-going discussion for a significant edit). It's been pulled from the canidates page but do we also need to replace the {{fac}} tag with the {{facfailed}} tag? - Davandron | Talk 16:08, 13 December 2006 (UTC)

Well no one had an answer, and User:Raul654 just removed the tag, so I'm going to place the facfailed tag. Its worth noting that we might be ready for another FA nomination. - Davandron | Talk 20:10, 10 January 2007 (UTC)

I guess having the facfailed is more confusing than not having it, since the FA discussion article was deleted. Its easier to just resubmit than get a low-value discussion page restored. I'm going to take down the failed tag; do we feel the article is ready for a new nomination? - Davandron | Talk 21:34, 10 January 2007 (UTC)

I suggest a peer review prior to approaching FAC - a quick glance shows this article could benefit from peer review before approaching FAC. Also, please do not add the facfailed tag, as the article never went through FAC, and that will incorrectly categorize the article. facfailed categorizes articles in a way that we would expect to find a failed fac in the archives, and there was never a fac review. SandyGeorgia (Talk) 22:29, 10 January 2007 (UTC)

Kalman filter reference in GPS ground control

I have put back in the reference to the Kalman filter because, to be quite honest with you, the kalman filter is the heart and the soul and the life-blood of GPS. It is my ever consuming thought as we upgrade the GPS control system. Everything takes a back seat to the kalman filter in GPS control. You might as well not talk about GPS ground segment if you fail to mention it. You don't even need Kwaj, Cape, or any of the other monitor sites or ground antennas. GPS could fly just fine with other monitor sites and other Air Force antenna systems (it would be messy, but it would work). But without the kalman filter - there is no GPS. Its the black magic behind GPS that makes it go. It would be like talking about Hendrix and not talking about his guitar. the other steve jobs 1910, 22 December 2006 (MST)

My apologies for it getting dropped in the edit and thank you for resorting it. - Davandron | Talk 17:54, 23 December 2006 (UTC)

No problem. I am heartened by the professionalism and courtesy i've found here. As information is available and suitable, i'll bring it up here as is prudent. I will say that AEP is coming soon - that is not news - but trying to switch to it while keeping the constellation flying will make switching the engines on a C-130 at 20,000 feet seem easy. Fear not, there's a crack team working on it. the other steve jobs 1900, 28 December 2006 (MST)

I have re-edited the ground segment portion because it was reading very poorly with very long sentences. I also added some facts to be more accurate. 1. We also can fly the birds with AFSCN, not just GPS-owned GAs 2. We don't just rely on the GPS-owned monitor stations (we could actually be fine without them in a pinch) - we use many other monitor stations besides CAPE/KAWJ, etc. every day because kalman filters love data.

I also tried to make it smoother by putting the kalman filter reference (which was in the first sentence) over next to where we're talking about the inputs to it (which was in the last sentence) since that seemed to make more sense. I also referred to 2 SOPS as... well, 2 SOPS, because no one calls it day-to-day as the 2nd Space Operations Squadron, so i left the formal name in, and then started a new thought and called them 2 SOPS. I apologize to anyone who's worked on this - i'm not slinging mud and i appreciate all the hard work - but i read it, and by the 3rd time i read it as it was, it was still not making much sense to me. Hopefully, this change is okay. Yes... GPS ground segment is my life. It not only pays my bills, but its also very interesting to me.the other steve jobs 1400, 3 Jan 2007 (MST)

Its great to have a good resource such as yourself contributing. I may have undone your edit, but allow me to explain. In general throughout the article, acronyms are spelled out the first time they are used to aid in understanding what the mean. I think it should be the same for 2nd Space Operations Squadron and 2 SOPS as it is potential very confusing to a non-military individual. Once that first occurrence is spelled out, I think its perfectly acceptable to use 2SOPS throughout the article. - Davandron | Talk 18:33, 18 January 2007 (UTC)

Whoops! that was my intention, and obviously fat fingered it. Thanks for correcting it for me.! The other steve jobs 21:42, 22 January 2007 (UTC)

Satellite Launches/Decommisions appropriate for article?

What is everyone's feeling on the launch / decommission dates for the satellites being in the article? GPS meetings' presentations sometimes contain a stacked, horizontal bar chart (a form of timeline, i guess) showing the commission / decommission dates for each vehicle; providing a feel for how many active satellites there are and how old they are.

Perhaps a stand alone template or stub? - Davandron | Talk 17:44, 2 January 2007 (UTC)

Yes. I think its quite appropos. I mean, if we're talking about the USAF GPS system (which we are), this is the place you ought to be able to find all the data. If we don't put in a table, at least we should link to a page that has it. But its not like we're decomming birds every week - so i think its something this page should be able to keep up with. the other steve jobs 1400, 3 Jan 2007(MST)

I think this would need to be a stand-alone article. The GPS article is quite long already, and is still missing some important info and refs (I am working on researching and augmenting it). Properly done, the launch article should have lots of references, and this would also clutter up the main article.Dhaluza 00:16, 4 January 2007 (UTC)

Yeah it is a little too bit already... I think I'll author a main article titled something like "GPS Satellites" which could also explain the different blocks / versions then link it into the space segment. Thanks! - Davandron | Talk 03:00, 4 January 2007 (UTC)

Reorg

I wanted to add the GPS segmentation terminology, and had to do some work to organize the TOC hierarchy to fit it in. This lead to more changes to pull things together. I did it in steps to try to make it easy to follow, but the wiki change comparison does not work well with moves. Anyway, rest assured that I did not delete anything. I did add some intro text and formatting. Dhaluza 01:34, 3 January 2007 (UTC)

Daily Update links

UPDATE: I'm restoring the original link (keep both); apparently the problem was related to how I was connecting. From other connections I can see the files originally pointed to and they do contain a lot of information. Please disregard the original posting below - Davandron | Talk 03:20, 4 January 2007 (UTC)
I replaced

http://tycho.usno.navy.mil/gpscurr.html "Current GPS constellation, updated daily"

with this site

http://www.navcen.uscg.gov/gps/status_and_outage_info.htm

The original link seems to contain little information, and when I click the links I get authorization errors. The replacement is available everywhere and includes resources to understand what the status messages. - Davandron | Talk 15:29, 3 January 2007 (UTC)

Removed link

As I was organizing the links, I removed the following:

• University of New Brunswick, In Simple Terms, How Does GPS Work?

If you goto that page, it contains very little information, all of which appears in the main article and its sources already. However, we are all fallible, so please correct me if this is a valuable source. - Davandron | Talk 03:30, 4 January 2007 (UTC)

Navigation versus Aids to Navigation

I have loved using GPS for the past ten years, but as a former USAF Navigator, it's important for the reader's safety to prominently recognize that ANY electronic system is an aid to (something that eases or speeds determing your position) and not a substitute for navigation itself (accurately determining your position). Aids fail, batteries go dead, power supplies and wiring fail and the prudent voyager still needs to be able to safely get where they're going using manual means.

That's why both USAF and USCG call this and other system an electronic aid to navigation. Some recent deaths in the northwest may have been caused by overdependence on electronic navigation without manual back-up. So lets keep that critical word right in the beginning of the article, even though GPS is fairly reliable. The primary weak link in it is the user receiver's power source, and short of attaching AA cells to every fifth tree, that's not going to change. Thanks GCW50 17:10, 12 January 2007 (UTC)

GCW50, I completely agree with you that GPS can be an electronic aid to navigation, and we are in agreement with what actions are "best practices" in the world. However, this does not seem an appropriate warning or discussion for the lead-in of the article. And I do not agree with your usage of the world navigation.

I would link the discussion of navigation, but you have changed that article to re-enforce your changes here. So looking to the Merriam Webster dictionary, we find that navigation is associated not with a position-determination but with a course and distance, especially with regard to vessels. This seems at odds with your definition.

I'd ask for others to weigh in on this matter, to build a dialog of more than two individuals. - Davandron | Talk 03:06, 16 January 2007 (UTC)

Actually, the Meriam Webster dictionary says "the science of getting ships, aircraft, or spacecraft from place to place; especially : the method of determining position, course, and distance traveled" I don't see much difference with what I put in Navigation You always have to determine your postion first before you can lay a course to your destination. GCW50 14:42, 17 January 2007 (UTC)

Control segment and Calculating positions

On the Control segment text, we find that ...updates synchronize the atomic clocks on board the satellites to within one microsecond.... GPS uses time*speed-of-light as a distance measure, and 1e-6s*3e8m/s = 300 meters. So, this means that the satellites my GPS receiver is tracking may have a clock deviation between them of about 300 m! That's a bit different from the Satellite clock errors of +/-2 meters stated in Accuracy and Error Sources. +/-2 meters < 10nanoseconds. And this is a number that sounds better, otherwise why would we need atomic clocks... In fact, the error between satellite clocks is assumed to be very small, so that the basic equations used in the kalman filter (or least-squares algorithm) that yield the position solution, assume it to be included in a white noise component that represents all the unmodelled noise sources. This brings me to the second comment. The satellites use atomic clocks, but the GPS receiver uses a crystal oscilator. Good clock error models and some electronic advances make these clocks very good already, but just as the atomic clocks are constantly being corrected from the main control centre, so must the receiver clocks also be corrected. This is done at the receiver, by introducing a 4th unknown in the equations, the receiver clock bias (the other 3 are x,y,z or lat,lon,alt ...). The receiver-clock-bias*speed-of-light is a distance, an error which will be common to all satellite pseudorange measurements. That's why we need to see at least 4 satellites and not just 3. This is not mentioned there. My final comment goes for the paragraph Calculating a position with the P(Y) signal ...The encryption is essentially a safety mechanism... in Calculating positions. The pseudo-random sequences have a bit more magic about them than what is described here. They are periodic, therefore pseudo-random, but would they be infinite random sequences and the result of the correlation in time between any 2 different sequences would always yield zero. This is the fundamental aspect behind the fact that you can receive simultaneously on the same frequency, the signal from multiple satellites. Once a correlator choses a satellite ID, that pseudo-random sequence will correlate very well with itself and very poorly with all others. In fact, this way of transmitting digital information allows the signals to be reachable to the receiver when their power is already bellow the background noise level. In other words, the encryption is not just a safety mechanism to distinguish between real and whatever satellites. If you don't have the key, you cannot produce an identical P sequence, therefore you need certainly more than week computing power to manage to decode the information using some brute-force method... and then, they change the key and we go back to square 1. If the only reason preventing us from reading the P code would be the kind of things that happen on a war-like scenario, I think most of us living in peacefull places would have already found a way to read it anyway and cancel that ionospheric delay once and for all. At least, while there's peace there would be 30cm accuracy against 15m :). My personal comment on the way this particular paragraph is written is that it sounds way to much like "the war on terror", the "be affraid, be very affraid" kind of feeling that we Europeans feel to be so strong on the US. The RAIM will not help us! Oh my god!... —The preceding unsigned comment was added by 130.161.79.207 (talk • contribs) 20:27, 18 January 2007 (UTC)

WOW thats a lot... lets see if we can break it apart into what you are saying / talking about

1. If satellites are only synchronized to 1uS isn't that 300m error?
2. Need to mention using a 4th satellite to correct crystal oscillator drift
3. P(Y) Encryption's purpose

I'll take a crack at them.

1. There appears to be a misunderstanding between time transfer (the act of synchronizing the clocks) and the accuracy of the clock. While the atomic clock is repeatable to a very high standard, its synchronization to the reference station is only repeatable to 1uS. This does not impact the navigation component. It would matter if you were trying to synchronize your clock to the reference clock used by the gps control network.
2. This is actually mentioned in the simple introduction. Perhaps it should be explained in more detail elsewhere in the article.
3. You mentioned many things about the P(Y) encryption. Here is a short answer. Yes, the very long PRN increases correlation gain, however thats just the P-code. Relatively recently, they decided to encrypt the long P-code, and thats where the Y part comes from. Believe it or not it is primarily as an assurance / antispoofing. As I understand it, the encryption not to stop someone from post-processing the data and decrypting the code, its to stop someone from correctly encrypting a fake signal and introducing intentional error into those accessing the P(Y) channel. By the way, you'll be happy to know smart people have figured out how to use the L2 data stream to cancel out ionospheric delay. This is called codeless or semi-codeless multifrequency decoding and its used in the survey industry. Thats a peaceful industry that likes high-accuracy, but its not easy to do (and the smart people like getting paid to figure it out).

I think all the issues you raised are already covered in the article, and hopefully my explanations help. If people reading this feel that the article needs to be expanded, please feel free to discuss who we should do that. Enjoy. - Davandron | Talk 21:41, 18 January 2007 (UTC)

Additional Archives

This talk page is pretty active! It's hard to strike the size / discussion balance. I've moved the discussions which were last commented on in November 2006 into /Archive 2 and given it the title November 2006. There wasn't a lot, so I think when we're ready to move December 2006, we should move it into Archive 2 and change the link-text to read as such.

I would like to keep 2 months of discussion on this page, but that might be hard. How does the group feel about performing an archiving on Feb 1st of the discussions last commented on Dec 1 - Dec 15? Will those be old enough? - Davandron | Talk 22:17, 18 January 2007 (UTC)

Corrected DOD restriction information

Under the military section, it stated a general speed limitation of 515m/s and that no GPS receiver can operate above 18km. This restriction, which only applies to civilian recievers, is incorrectly stated. Both conditions must be present (18km+ and 515m/s+) in order for the GPS to cease providing information. I've used commercial GPS recievers in high altitude balloons on 2 occasions that exceeded 18km, but not 515 m/s without a problem. Achilles03 15:56, 19 January 2007 (UTC)

Thanks for clarifying that subject. I've edited your entry to removed a redundancy, and took the opportunity to improve the copy of the section as a whole. - Davandron | Talk 18:28, 19 January 2007 (UTC)

Potential Linkspam

Removed this addition by 68.147.203.19

* [http://www.gpspolice.net/videos.php GPS technology fights crime.] 
 CTV news broadcast (video) of how GPS technology helped RCMP break-up a crime ring.

This user previously added a similar link (Dec 28th) to a similar article. - Davandron | Talk 14:09, 22 January 2007 (UTC)

NGA Monitor stations

Sorry for the coyness of my addition of the text "and other sources" with reference to what feeds the Kalman filter with L-band data. This [9] makes it plain that its open source that we're using NGA data to feed the machine. In fact, its a huge help and will only get better in the future with more NGA sites coming online in the future, since we'll be able to "reverse locate" the birds - as in, you find your position by seeing 3 or more birds now, well, we'll be able to see their precise location by using 3 monitoring stations at any given time. The other steve jobs 21:39, 22 January 2007 (UTC)

Great find on the source! We actually had an edit conflict because the original link (to the email list) probably wasn't reliable enough for Wiki-standards. This new one is a lot better. If you know of some more data on the NGA's website or in some presentations made by your colleagues, that might help too.

BTW, I went ahead and reformatted your source/reference so that its a reference-noted format. Its a requirement for articles that want to get the WP:Featured Article status. - Davandron | Talk 21:54, 22 January 2007 (UTC)

NGA didn't change their name from NIMA to a 3 letter acronym that ends with "Angecy" because they want to tell the world about what they do. ;-) For the record, I will always tred on the side of too cautious because i have no desire to put the mission in jeopardy in any way - so please forgive me and feel free to remove any edits that don't meet Wiki standards, and i promise not to be offended. As for now, like the link states, they've got their monitor stations and they're feeding their data to us so as to make the NAV messages better. Honestly, they're a black box that has a spigot to us, and that's really all we need to know. The other steve jobs 20:09, 24 January 2007 (UTC)

Removed "gps to add 16-bit year" claim

I removed the following unsupported claim

A new field is being added to the GPS navigation message 
that specifies the calendar year number exactly, in a sixteen-bit field

after double checking both the current or purposed modernized specifications. There was no mentioned anywhere of this addition. If someone has a reliable source that this is being added, please feel free to restore the text. - Davandron | Talk 19:47, 23 January 2007 (UTC)

Not going to happen. In coversation with the person on planet earth that would have to know about it in order for it to even be an idea (they'd have to go to his group to discuss the operational feasibility), he didn't have any idea what i was talking about. --The other steve jobs 20:47, 24 January 2007 (UTC)

Small Update: In the process of researching for the L2C and L5, I did learn that these new signals will use a 13-bit GPS week number (instead of the 10-bit currently used), which means it will only return to zero every 157.5 years. So, instead of needing to know the current decade, you will only need to know the current century... provided, of course, that GPS L2C signal is still around in the year 2138! Perhaps this is the change the original claim was referring to. - Davandron | Talk 20:56, 30 January 2007 (UTC)

Industry Links

Recently, anonymous user 81.255.195.105 added / proposed an Industry section of the external links, and added only the Magellan link. I removed this addition due to concerns about WP:EL, but it does raise the question; should we provide links to the manufacuters of GPS receivers? If so, which ones should be represented? - Davandron | Talk 17:39, 26 January 2007 (UTC)

• Oppose (weakly): While I like the idea and thank the user for adding it, I think its very thin ice and probably inappropriate for wiki; its not the wiki's job to provide a directory of manufactures, and the article itself is not about manufactures. - Davandron | Talk 17:39, 26 January 2007 (UTC)
• Oppose: Instead, how about one external link like this?: Pricegrabber.com GPS receivers —EncMstr 17:44, 26 January 2007 (UTC)
• Oppose: I think it would be more interesting to talk about the _actual_ recievers - the families of commerical GPS receiver chips out there. Garmin, Megellan, etc.. they all use those receivers in their... receivers. The history of how GPS receivers have gone from backpack-sized to now the size of a rice grain is even more interesting to me - from 4 channel receivers to now standard 12 + WAAS, etc. Its an incredible history. But consumer GPS receivers are approaching commodity status, with the only real differentiation being who's got the better software, and even THAT is becoming commodity rapidly. The other steve jobs 17:42, 30 January 2007 (UTC)