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I am working to produce a snow duration map in GEE, but since the area of interest is mountainous I am having trouble with north-facing slopes. I've learned that a solution exists for Sentinel in this answer: https://gis.stackexchange.com/a/305159/147843

Is there an equivalent for Landsat?

  • This is not equivalent to cloud shadow, but is rather a parallax sun-angle issue. This is why you orthorectify imagery in rugged terrain. And, yes it is common to orthorectify Landsat but, you will have to research GEE solutions, if any. – Jeffrey Evans Aug 15 at 14:45
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I'we been lead to an easy solution that may be useful to other users.

GEE provides the function ee.Terrain.hillShadow that allows to produce a band with 1 where the pixel is illuminated and 0 when it is in the shade, using a DEM. Then you just have to mask your image using the shadowmap.

Here is how i used it:

var image= ee.Image("LANDSAT/LT05/C01/T1_SR/LT05_195028_19841230")
var SRTM=ee.Image("USGS/SRTMGL1_003");
var elevation=SRTM;

var visu={bands:['B3','B2','B1'],min:0, max:3000};

var shadowMap=ee.Terrain.hillShadow(elevation, image.get('SOLAR_AZIMUTH_ANGLE'), image.get('SOLAR_ZENITH_ANGLE'),200,true).focal_median(2).reproject(elevation.projection());
image=image.addBands(shadowMap);
Map.addLayer(image.updateMask(image.select("shadow")),visu,'sun part');
Map.addLayer(image.updateMask(image.select("shadow").not()),visu,'shadow part');

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