Theia Snow observations

Theia snow observations are generated from Sentinel-2 (20m resolution, every 5 days or less) and Landsat-8 images over selected areas of the globe.

They can be downloaded using the theia_download command (see site to install and configure). Theia snow observation present in the form of tiles that can be merged to diplay a larger area. The folowing workflow present a method to download and merge tiles of Theia snow observations.

Donwload observations using theia_download:

mkdir zip
cd zip
python ../theia_download.py --lonmin=-2.40 --latmin=41.20 --lonmax=10 --latmax=49.22 -c Snow -a ../config_theia.cfg -d 2021-09-01 --snow_level L3B-SNOW

Unzip archives and create folder achitecture:

cd ..
mkdir unzip
unzip 'zip/*.zip' -d unzip
mkdir SCD SOD SMD
find unzip/ -name '*SOD_R2.tif' -exec cp "{}" SOD/ \;
find unzip/ -name '*SMD_R2.tif' -exec cp "{}" SMD/ \;
find unzip/ -name '*SCD_R2.tif' -exec cp "{}" SCD/ \;

We merge the tiles using gdalwarp bash function from GDAL:

gdalwarp SMOD/*.tif SMOD_mosaic.tif

Warning

The tiles have a small area overlap. Using this method, they are superimposed following file order of the command (last on top).

Perhaps orfeotoolbox is better for merging mosaics with overlay as there is a specific method for overlayed areas management (to be explored for future developments, can ask César for help)