GDAL
Aus Wiki
Convert UTM coordinates to Lon/Lat
gdalwarp -t_srs '+proj=longlat +datum=WGS84 +no_defs' input.tif output.tif
Cut area from GeoTiff
gdal_translate -projwin min_lon max_lat max_lon min_lat -projwin_srs EPSG:4326 -ot Float32 -of GTiff input.tif output.tif"