NULL Pointer error when trying to process a geojson file with no building footprints

[00krishna]

I ran the code below to convert the Spacenet 2 Khartoum dataset to SBD format.

python2.7 createDataSpaceNet.py /path/spacenet/AOI_5_Khartoum_Train/ \
           --srcImageryDirectory RGB-PanSharpen \
           --outputDirectory /path/spacenet/AOI_5_Khartoum_Train/sbd_labels \
           --annotationType SBD \
           --convertTo8Bit \
           --outputFileType JPEG \
           --imgSizePix 650

On buildings_AOI_5_Khartoum_img3.geojson the script crashed and I got the traceback below indicating a NULL pointer.

Traceback (most recent call last):
  File "createDataSpaceNet.py", line 317, in <module>
    bboxResize= args.boundingBoxResize
  File "createDataSpaceNet.py", line 110, in processChipSummaryList
    entry = lT.geoJsonToSBD(annotationName_cls, annotationName_inst, chipSummary['geoVectorName'], chipSummary['rasterSource'])
  File "/path/spacenet_utilities/python/spaceNetUtilities/labelTools.py", line 1066, in geoJsonToSBD
    my_inst_segmentation = createInstanceSegmentation(my_raster_source, my_vector_source)
  File "/path/spacenet_utilities/python/spaceNetUtilities/labelTools.py", line 1016, in createInstanceSegmentation
    cell_array[i] = createSegmentationByFeatureIndex(i, rasterSrc, vectorSrc, npDistFileName='', units='pixels')
  File "/path/spacenet_utilities/python/spaceNetUtilities/labelTools.py", line 1004, in createSegmentationByFeatureIndex
    dist_trans_by_feature = createDistanceTransformByFeatureIndex(feature_index, rasterSrc, vectorSrc, npDistFileName='', units='pixels')
  File "/path/spacenet_utilities/python/spaceNetUtilities/labelTools.py", line 950, in createDistanceTransformByFeatureIndex
    Feature_Layer.CreateFeature(my_feature)
  File "/path/python2.7/site-packages/osgeo/ogr.py", line 1727, in CreateFeature
    return _ogr.Layer_CreateFeature(self, *args)
ValueError: Received a NULL pointer.

The error seems to be caused by the geojson file having no building footprints in it. So the script passes this empty set of footprints to OGR and OGR interprets that as a NULL. I think the solution would be to check for an empty value before passing the value to OGR.

[nrweir]

Related to #97