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landsat_engreenland_crop1.ann
landsat_engreenland_crop1.ann

Greenland in the evening

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Thanks to pretty good weather in large parts of Greenland during July and early August there is some good satellite image material available for Greenland from this year. I took this opportunity to assemble two evening images, both of them based primarily on Landsat data from July which means this is not yet snow and ice minimum. The first is from the northeast:

This extends across about 12 degrees of latitude and well illustrates the character of nighttime images from satellites in sun synchroneous orbit. In the very north these are quite similar to the normal daytime images, in fact both converge towards the northern recording limit while further south images change more towards the later evening. To illustrate this here an arbitrary orbit of Landsat (path 24 and 40 if you want to know) with the row numbers indicated.

Row 246 is the top row between the descending (daytime) part and the ascending (nighttime) part. Here some approximate average sun azimuth directions from scenes with these rows:

row average sun azimuth
241 -74
242 -80
243 -87
244 -95
245 -105
246 -116
247 -125
248 -135
1 -144
2 -151
3 -158

As you can see as the satellite transits from night to day the average sun position moves from northwest (i.e. late evening) via west towards south. South direction is reached at row 9 (which is about 72° north) and then direction moves further to the southeast (i.e. morning) which is the typical viewing configuration for lower latitudes.

Here a few crops from different parts of the image.

One of the nice aspects of evening images from the northern hemisphere – apart from the low sun position producing a more dramatic rendering of the relief – is that the sun direction better matches the light direction we are used to for shaded relief so this kind of image is less prone to perceived relief inversion when being viewed by people not so used to the morning illumination more common in satellite images.

The second view is from western Greenland from Disko Bay near Ilulissat with the Jakobshavn Glacier. This also uses a few images from 2016.

Both images can be found in the catalog on services.imagico.de.

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