File:Ahaggar Landsat 8 pan sharpened composite.jpg

Original file (8,751 × 8,751 pixels, file size: 24.49 MB, MIME type: image/jpeg)

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Summary

Description	English: The Ahaggar, also known as the Hoggar, a volcanic mountain range in the central Sahara. The image is averaged from 58 Landsat 8-scenes, provided by NASA. Bands 4, 3, 2 and 8 were combined into an RGB image. Panchromatic sharpening, conversion to radiance, weighted averaging, and rescaling to extrema of the scenes was done in R with the package RStoolbox. JPEG-encoded with Guetzli. Images acquired in the range 18 July 2013 – 2 March 2021, each at mean 10:05, range 10:04–10:07. The sun position range: azimuth 86°–155°, average 133°; elevation 38°–69°, average 52°. Resolution: 15m. Projection: UTM 31 N, WGS84. Center: 769590, 2574870. From WRS-2 Path 192 Row 044. Deutsch: Das Ahaggar, auch bekannt als Hoggar, ein vulkanisches Gebirge in der zentralen Sahara. Das Bild ist gemittelt aus 58 Landsat 8-Aufnahmen, bereitgestellt von der NASA. Verwendet wurden die Kanäle 4, 3, 2 und 8 um ein RGB-Bild zu erzeugen. Die Aufnahmen wurden in R mit dem Paket RStoolbox panchromatisch geschärft, gewichtet gemittelt, und auf die Extrema skaliert. JPEG-enkodiert mit Guetzli. Aufnahmen aus dem Zeitraum 18 July 2013 – 2 March 2021, jeweils im Mittel um 10:05, Bereich 10:04–10:07. Der Sonnenstand rangiert im Bereich Azimuth 86°–155°, im Mittel 133°; Höhe 38°–69°, im Mittel 52°. Auflösung: 15m. Projektion: UTM 31 N, WGS84. Bildmitte: 769590, 2574870. Aus WRS-2 Path 192 Row 044.
Date	18 March 2019
Source	NASA, Own work
Author	Linus Wolf
Other versions	surface reflectance

Object location	23° 15′ 39.85″ N, 5° 38′ 06.26″ E	View this and other nearby images on: OpenStreetMap	23.261069; 5.635073

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File history

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	Date/Time	Dimensions	User	Comment
current	17:40, 19 March 2021	8,751 × 8,751 (24.49 MB)	Linus Wolf	increase number of input rasters to 58
	04:03, 21 December 2020	8,751 × 8,751 (24.49 MB)	Linus Wolf	increased number of input rasters to 54
	12:18, 4 August 2020	8,751 × 8,751 (24.37 MB)	Linus Wolf	increased number of input images to 49 while excluding a few; fixed a problem causing artefacts
	22:39, 13 July 2020	8,721 × 8,721 (24.04 MB)	Linus Wolf	+ 1 input raster; undid histogram matching (while fixing an error in weighted averaging), switched back to intensity-hue-saturation method for panchromatic sharpening, and changed scaling so that channels are not scaled separately
	16:35, 13 April 2020	8,693 × 8,693 (25.35 MB)	Linus Wolf	discarded one more input raster with clouds, added several which seem good in the extent used for this image. Switched to Brovey reweighting for panchromatic sharpening. Added histogram matching between input rasters (the change in color is noticeable, I think). Fixed an issue of missing values not being excluded in averaging.
	18:25, 24 December 2019	8,675 × 8,675 (23.67 MB)	Linus Wolf	added one new input raster; removed one which had clouds; set gamma correction to power 1.3
	00:47, 5 October 2019	8,654 × 8,654 (23.47 MB)	Linus Wolf	+ 1 input raster
	01:34, 12 May 2019	8,610 × 8,610 (23.09 MB)	Linus Wolf	+ 1 input raster; slight gamma correction
	01:16, 14 April 2019	8,482 × 8,482 (22.35 MB)	Linus Wolf	{{Information \|description ={{en\|1=The Ahaggar, also known as the Hoggar, a volcanic mountain range in the central Sahara. The image is averaged from 32 Landsat 8-scenes, provided by NASA. Bands 4, 3, 2 and 8 were combined into an RGB image. Co-registration, weighted averaging, and rescaling to extrema of the scenes was done in R with the package [https://bleutner.github.io/RStoolbox/ RStoolbox]. JPEG-encoded with [https://github....