Resampling to EPSG:4326 produces unexpected results

[pnuu]

Code Sample, a minimal, complete, and verifiable piece of code

Area definition

REGION: EPSG4326 {
   NAME:    Global equal latitude/longitude grid for global sphere
   PCS_ID:  EPSG:4326
   PCS_DEF: init=EPSG:4326
   XSIZE: 8192
   YSIZE: 4096
   AREA_EXTENT:  (-180.0, -90.0, 180.0, 90.0)
};

import glob
import sys
from satpy import Scene

def test_msg(composite):
    fnames = glob.glob("/home/lahtinep/data/satellite/geo/H*MSG3*201801110900*")
    glbl = Scene(reader='hrit_msg', filenames=fnames)
    glbl.load([composite])
    lcl = glbl.resample('EPSG4326')
    lcl.save_dataset(composite, '/tmp/%s_msg.tif' % composite)

def main():
    composite = sys.argv[1]
    test_msg(composite)

if __name__ == "__main__":
    main()

Problem description

Resampling SatPy scenes to global lat/lon grid (EPSG:4326) produces a row of tiny images along the equator.

Expected Output

Single image located at the correct place.

Actual Result, Traceback if applicable

Versions of Python, package at hand and relevant dependencies

• Doesn't work with any SatPy xarray/dask branch, e.g. develop
• Works with maint/0.8 branch
• All of the other packages stay the same, only SatPy branch is changed

[pnuu]

I had a look in to the code, but can't figure out what is causing this. I think it's either something in resample.py in SatPy, or pyresample.kd_tree.XArrayResamplerNN class that is used in develop branch to handle resampling.

[djhoese]

And you're sure it isn't anything in the reader? You mentioned on slack that you've seen this issue in past versions of mpop/satpy but it was fixed at some point, right? Does it happen for non-composites? Does it happen for all resolutions?

[pnuu]

Can't see how reader updates would affect, resampling to other areas (e.g. EPSG:3035) work fine. It might have been something about the poles being part of the area definition the last time. @mraspaud does that ring a bell? I tried with a single channel that wasn't defined as a composite (IR_108), same thing. Also smaller images have the same issue, tried with 800x400 resolution.