Feature request: support GDAL >= 3

[araichev]

Currently multigtfs is not compatible with GDAL >= 3. Can we make it compatible, and is that sensible? My company is willing to fund this feature request.

As far as i can tell, the only incompatibility is that GDAL >= 3 requires WGS84 coordinates to be specified in latitude-longitude order by default; they can be specified in longitude-latitude order as is done in multigtfs, but doing so now requires a special flag; see the GDAL docs.

Creating longitude-latitude geometries with multigtfs and GDAL >= 3 appears to work at first ---no errors are thrown--- but those geometries are actually malformed and certain methods fail on them, e.g. the transform() method raises a GDALException. Here's an example on Linux Mint 19.3 with Python 3.7.6, GDAL 3.0.2, and Django 2.2.10.

Python 3.7.6 (default, Dec 19 2019, 23:50:13) 
Type 'copyright', 'credits' or 'license' for more information
IPython 7.12.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from django.contrib.gis.gdal import OGRGeometry                                   

In [2]: point = OGRGeometry("POINT(174.74 -36.840556)", srs=4326)  # WGS84 lon-lat            

In [3]: point.transform(2193, clone=True)   #Transform to NZTM                                                  
---------------------------------------------------------------------------
GDALException                             Traceback (most recent call last)
<ipython-input-4-898671070db8> in <module>
----> 1 point.transform(2193, clone=True)

~/.virtualenvs/gtfs_explorer/lib/python3.7/site-packages/django/contrib/gis/gdal/geometries.py in transform(self, coord_trans, clone)
    409         elif isinstance(coord_trans, (int, str)):
    410             sr = SpatialReference(coord_trans)
--> 411             capi.geom_transform_to(self.ptr, sr.ptr)
    412         else:
    413             raise TypeError('Transform only accepts CoordTransform, '

~/.virtualenvs/gtfs_explorer/lib/python3.7/site-packages/django/contrib/gis/gdal/prototypes/errcheck.py in check_errcode(result, func, cargs, cpl)
    116     Check the error code returned (c_int).
    117     """
--> 118     check_err(result, cpl=cpl)
    119 
    120 

~/.virtualenvs/gtfs_explorer/lib/python3.7/site-packages/django/contrib/gis/gdal/error.py in check_err(code, cpl)
     57     elif code in err_dict:
     58         e, msg = err_dict[code]
---> 59         raise e(msg)
     60     else:
     61         raise GDALException('Unknown error code: "%s"' % code)

GDALException: OGR failure.

In [4]: point = OGRGeometry("POINT(-36.840556 174.74)", srs=4326)  #WGS84 lat-lon                         

In [5]: point.transform(2193, clone=True).coords  #Transform to NZTM and display coordinates                                          
Out[5]: (5921452.26055115, 1755039.2190557136)

[araichev]

I guess the compatibility could be accomplished by adding a boolean option (that defaults to False) to the multigtfs import command, e.g. use_lat_lon_order, to import geographic coordinates in lat-lon order.

[araichev]

@jwhitlock any word on this? I forgot about this feature request and now need it again.

[jwhitlock]

@araichev, I haven't looked closely at the GDAL change, but it sounds good to me (latitude / longitude is how I think of coordinates anyway), and your ideas for handling this transition sound good. I haven't had time to work on multigtfs for a while, and I don't see that changing this year.

[jspetrak]

@araichev If you have chance to provide PR for this issue, feel free to do so. The project will add few new maintainers to run it further. Thank you.