i.sentinel.import: wrong resolution set for latlong locations

[veroandreo]

Name of the addon i.sentinel.import

Describe the bug When trying to import S2 scenes into a latlong location using i.sentinel.import with -r flag, the resolution is set to 10, 20 or 60 degrees instead of the equivalent of 10, 20 and 60 m in degrees. If I import into a UTM location all is fine, as well as if I use r.importinstead of i.sentinel.import with a latlong location. As you can see below, r.import estimates a resolution, however, r.sentinel.import uses the nominal resolution in meters anyway.

To Reproduce Steps to reproduce the behavior:

1. Download a S2 scene

   i.sentinel.download settings=your_sentinel_file output=tmp uuid=541021f8-63f5-4e9d-ba28-425c4c8451df

2. Import into a latlong location - here, I already got messages that the imported map was empty

   i.sentinel.import input=tmp/ pattern='B(02_1|03_1|04_1|08_1|8A_2)0m' extent=input memory=500
   ...
   Estimated target resolution for input band
   <T21JYM_20200126T134201_B11_20m>: 0.00018606630466763683
   Using given resolution for input band <T21JYM_20200126T134201_B11_20m>:
   20.0
   Reprojecting <T21JYM_20200126T134201_B11_20m>...
   ERROR: The reprojected raster <T21JYM_20200126T134201_B11_20m> is empty
   Writing metadata to maps...

3. Run r.info to check (see below)

Screenshots

System description (please complete the following information):

• Operating System: Linux Fedora 31
• GRASS GIS version 7.9 (dev)
• with python 3.7.4 because of ctypes problem

[neteler]

Probably we need a change here for LongLat:

https://github.com/OSGeo/grass-addons/blob/f5b90b741b09a63269ee8e782ebcc43378018a08/grass7/imagery/i.sentinel/i.sentinel.import/i.sentinel.import.py#L229

[veroandreo]

ping @landam :) any chance to have a look at this?

[lucadelu]

Probably we need a change here for LongLat:

https://github.com/OSGeo/grass-addons/blob/f5b90b741b09a63269ee8e782ebcc43378018a08/grass7/imagery/i.sentinel/i.sentinel.import/i.sentinel.import.py#L229

The change should be done in _raster_resolution function, the problem it is to get the right value in degree according to the position on the Earth surface.

Could geodesic lenght be useful?

[neteler]

... the problem it is to get the right value in degree according to the position on the Earth surface.

Could geodesic lenght be useful?

We have length_geodesic(), maybe interesting?

• doc: https://grass.osgeo.org/grass79/manuals/libpython/pygrass.vector.html?highlight=length_geodesic#pygrass.vector.geometry.Line.length_geodesic
• code: https://github.com/OSGeo/grass/blob/90634b76e3bcf9695a844cf3f6581975fa7283d9/lib/python/pygrass/vector/geometry.py#L848

[veroandreo]

In this commit in the i.landsat.import addon I propose a simple approach, i.e., using r.import's resolution = estimated when the target location is longlat. What do you think @neteler and @lucadelu ?

[lucadelu]

It could work, did you try if you addons works properly?

[veroandreo]

It could work, did you try if you addons works properly?

Yes, It works as expected. It's r.import who does the resolution estimation for latlong locations.