adugnag / gee_s1_ard

Creates an analysis ready sentinel-1 SAR image collection in Google Earth Engine by applying additional border noise correction, speckle filtering and radiometric terrain normalization.
MIT License
233 stars 83 forks source link

Update terrain_flattening.js #5

Closed adugnag closed 3 years ago

adugnag commented 3 years ago

There was an error in the calculation of the aspect and heading angle. The original implementation in (Hoekman and Reiche 2015) expects angles from -180 to 180, while the aspect computed in GEE is from 0 to 360. In addition, the aspect angle on GEE seems downhill directed, while it should be uphill.

As a result, the correction factor needs to be multiplied by gamma0 instead of being divided.

All this is corrected in the updated version.