The Template:Location_map_skew shows a location map as a composite image of an existing map in either equirectangular projection or skewed projection, with multiple (up to 4) markers and optional labels superimposed onto it. This template functions in the style of Template:Location_map, but allows 4 markers and labels (rather than just one marker). Note: For brevity, parameters "pos" & "bg" are aliases (for "position" & "background").
{{Location map skew
|locname (selected from templates named "Location_map_<locname>")
|skew = number < 1.0 for narrow or > 1.0 for wider longitude
(skews more towards top of map)
------------------------------------------- 1st label & marker
|label = 1st label text
|label_size = 1st label font size, percent (such as "85")
|position = pos = left or right or top or bottom – position of
1st label relative to 1st mark (default: right)
|background = bg = background color for 1st label, defaults transparent
|lon_dir=W 1st longitude direction: W=west, E=east (default)
|lat_dir=S 1st latitude direction: S=south, N=north (default)
|lat_deg = 1st latitude degrees
|lat_min = 1st latitude minutes
|lat_sec = 1st latitude seconds
|lon_deg = 1st longitude degrees
|lon_min = 1st longitude minutes
|lon_sec = 1st longitude seconds
|lat = 1st latitude (as decimal; negative for south latitude)
|long = 1st longitude (as decimal; negative for west longitude)
|mark = 1st marker image file name, a red dot by default
|marksize = 1st marker size, default=8 (pixels wide/tall)
------------------------------------------- 2nd label & marker
|label2 = 2nd label text
|label2_size = 2nd label font size, percent (such as "85")
|position2 = pos2 = left or right or top or bottom – position of
2nd label relative to 2nd mark (default: right)
|background2 = bg2 = background color for 2nd label, defaults transparent
|lon2_dir=W 2nd longitude direction: W=west, E=east (default)
|lat2_dir=S 2nd latitude direction: S=south, N=north (default)
|lat2_deg = 2nd latitude degrees (or use combined lat2)
|lat2_min = 2nd latitude minutes
|lat2_sec = 2nd latitude seconds
|lon2_deg = 2nd longitude degrees (or use combined long2)
|lon2_min = 2nd longitude minutes
|lon2_sec = 2nd longitude seconds
|lat2 = 2nd latitude (as decimal; negative for south latitude)
|long2 = 2nd longitude (as decimal; negative for west longitude)
|mark2 = 2nd marker image file name, a red dot by default
|mark2size = 2nd marker size, default=8 (pixels wide/tall)
|skew2 = number < 1.0 for narrow or > 1.0 wider longitude.
------------------------------------------- 3rd label & marker
|label3 = 3rd label text
|label3_size = 3rd label font size, percent (such as "120")
(... similar latitude/longitude parameters named "~3" ...)
|mark3 = 3rd marker image file name, a red dot by default
|mark3size = 3rd marker size, default=8 (pixels wide/tall)
|pos3, bg3 = 3rd label position & background color
|skew3 = number < 1.0 for narrow or > 1.0 wider longitude.
(...repeat until label7/mark7...)
-------------------------------------------
|border = border color or none
|caption = map caption; for no caption enter "caption=";
if omitted, then the caption will be auto-generated
as: "<marker #1 label> (<location map name>)"
|float = left or right or center or none for map placement
|width = map width for display size
|AlternativeMap = Alternative map file name (changes background map,
border coordinates are determined based on the map name);
this is only recommended for use in templates
}}
Parameter locname refers to {Template:Location map locname} containing the image name and coordinates of a particular map.
Find an appropriate blank map in equirectangular projection (otherwise, coordinates will drift off, typically further north)
Create a template named "Template:Location_map_locname" (copy the content of any other map template into it and enter appropriate values).
Set default parameter values (using those parameter names), such as setting "mark" with image-file name and "marksize" for pixels wide/tall, or set default label font size ("label_size = 78" percent).
Parameter names not used by "Template:Location_map" will be ignored by it, and only used for multiple-markers (such as defaulting "label2_size = 78" percent, or "mark2size=7" pixels).
The skewing of map coordinates, when placing markers/labels on the map image, is performed by a linear interpolation of the longitude relative to the height of the latitude (higher latitudes skew longitude more). A skew factor < 1.0 squeezes longitudes together near the top latitudes, while a skew factor > 1.0 spreads longitudes apart near the top.
The formula is roughly:
To skew by latitude ratio (skewing longitude more towards top):
The map with markers/labels is implemented as nested HTML divisions. The map-box is in an HTML division, containing the map-image division, then containing each point as a percent-locator division containing a marker-image sub-division plus a label sub-division. Each point is calculated (for a percent-locator division) with X or Y coordinate "XX.X%" or "YY.Y%" as follows:
The div-tag is "<div style="position: absolute; z-index: 2; top: XX.X%; left: YY.Y%; ...>"