MODIS l1b reader seems to switch latitude and longitude for 500m data

[TAlonglong]

To me it seems the latitude and longitude data are switched for 500m data.

#!/usr/bin/python

from satpy.scene import Scene

from satpy.utils import debug_on
debug_on()

files = ['/data/pytroll/testdata/modis/MYD02Hkm_A19133_135516_2019133140523.hdf',
         '/data/pytroll/testdata/modis/MYD03_A19133_135516_2019133140523.hdf']

ql = Scene(filenames=files, reader='modis_l1b')

ql.load(['longitude'], resolution=500)
print(ql['longitude'])
print(ql['longitude'].data.compute())

Expected behavior
Keeping in mind this data is read directly from satellite the longitude should be around 30W to 30E or around that.

Looking with hdfview I see for longitude values like that.

Actual results

[DEBUG: 2019-05-16 09:23:33 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/data/software/conda-pytroll/lib/python3.7/site-packages/satpy/etc'
[DEBUG: 2019-05-16 09:23:33 : satpy.readers] Reading ['/data/software/conda-pytroll/lib/python3.7/site-packages/satpy/etc/readers/modis_l1b.yaml']
[DEBUG: 2019-05-16 09:23:33 : satpy.readers.yaml_reader] Assigning to modis_l1b: ['/data/pytroll/testdata/modis/MYD02Hkm_A19133_135516_2019133140523.hdf', '/data/pytroll/testdata/modis/MYD03_A19133_135516_2019133140523.hdf']
[DEBUG: 2019-05-16 09:23:33 : satpy.composites] Looking for composites config file modis.yaml
[DEBUG: 2019-05-16 09:23:33 : satpy.composites] Looking for composites config file visir.yaml
[DEBUG: 2019-05-16 09:23:33 : satpy.readers.yaml_reader] No coordinates found for DatasetID(name='longitude', wavelength=None, resolution=500, polarization=None, calibration=None, level=None, modifiers=())
[DEBUG: 2019-05-16 09:23:33 : satpy.readers.hdfeos_base] Interpolating from 1000 to 500
<xarray.DataArray 'add-1e094849281ac4ba1c070bc3284b4854' (y: 7260, x: 2708)>
dask.array<shape=(7260, 2708), dtype=float64, chunksize=(2420, 2706)>
Dimensions without coordinates: y, x
Attributes:
    standard_name:        longitude
    valid_range:          [-90.0, 90.0]
    units:                degree
    start_time:           2019-05-13 13:55:27.516430
    end_time:             2019-05-13 14:04:24.048077
    name:                 longitude
    resolution:           500
    calibration:          None
    polarization:         None
    level:                None
    modifiers:            ()
    ancillary_variables:  []
[[43.5406638  43.54028421 43.53990468 ... 39.59643028 39.58894565
  39.58146922]
 [43.54972929 43.54933826 43.54894728 ... 39.60496122 39.59748898
  39.59002492]
 [43.55879492 43.55839244 43.55799002 ... 39.61344222 39.60598237
  39.59853069]
 ...
 [75.48570661 75.48878629 75.49186542 ... 66.40679581 66.38974544
  66.37268247]
 [75.49471692 75.49778325 75.50084903 ... 66.41235377 66.39531103
  66.3782557 ]
 [75.5037265  75.50677947 75.50983195 ... 66.41758721 66.40055211
  66.38350441]]

Here the longitude is, checking in hdfview the values corresponding to the latitude values.

Environment Info:

• Linux
• Satpy Version: 0.15.0

[TAlonglong]

Checking the same for latitude I see values corresponding to the longitude values showed in hdfview.

[TAlonglong]

Could the problem be here?
https://github.com/pytroll/satpy/blob/master/satpy/readers/hdfeos_base.py#L255

[TAlonglong]

Swithcing lat/lon in the code mentioned above gives correct results.

[mraspaud]

@TAlonglong nice catch! Are you fixing this in a PR ?