sometimes nodata value is incorrect in the original files e.g. fractional_snow_cover

[JeroenVerstraelen]

I had a look:
it happens for sentinelhub based collections, that use the default sampletype, which is uint16.
This sampletype is mapped to the default geotrellis uint16 celltype, with 0 as nodata value.

I'm not sure if sentinelhub supports nodata values at all, but it is perhaps best if we can effectively configure it in layercatalog.json.
The 'quickfix' would be to set the default nodata value to something else (short.maxvalue), but that would suddenly change behaviour for a lot of collections. We would have to go over the list and think about it for each one of them.

Other 'quickfix' is to set sample type of fractional snow cover collection to float, this would solve thing in very short term, so maybe I'll start with that.

[EmileSonneveld]

import openeo
import sys

url = "https://openeo-dev.vito.be"
connection = openeo.connect(url).authenticate_oidc()

snow_cube = connection.load_collection(
    collection_id="FRACTIONAL_SNOW_COVER",
    spatial_extent={
        "west": 11.58,
        "east": 11.68,
        "south": 46.96,
        "north": 46.98,
    },
    temporal_extent=["2018-02-10", "2018-02-13"],
    bands=["NDSI"],
)

job = snow_cube.create_job(title="FRACTIONAL_SNOW_COVER")
job.start_and_wait()
job.get_results().download_files()

The nodata value should change from 0 to 255 for this layer

openeo-geotrellis-extensions/geotrellis-sentinelhub/src/main/scala/org/openeo/geotrellissentinelhub/ProcessApi.scala

Lines 212 to 213 in 3abdcb6

	// unless handled differently, NODATA pîxels are 0 according to
	// https://docs.sentinel-hub.com/api/latest/user-guides/datamask/#datamask---handling-of-pixels-with-no-data

[EmileSonneveld]

Now on openeo-dev:

Note that clouds are marked as 205 an can be manually masked away:
snow_cube = (snow_cube * 1.0).mask(snow_cube == 205)
https://collections.sentinel-hub.com/hrsi-fsc/