fiona.transform.transform - different behavior based on GDAL version

[calebrob6]

fiona.transform.transform exhibits different behavior based on the underlying gdal library installed.

Expected behavior and actual behavior.

If I run fiona.transform.transform("epsg:4326", "epsg:3857", [-75.71], [38.06]) I expect to get: ([-8427998.647958742], [4587905.271362515]) regardless of library version, however with gdal 3.0.2 and fiona 1.8.13.post1 I get the incorrect result.

In particular, the xs, ys position are swapped in the arguments, i.e. if I run fiona.transform.transform("epsg:4326", "epsg:3857", [38.06], [-75.71]) then I do get the correct result.

@snowman2 suggested that this could be related to a PYPROJ issue, pyproj4/pyproj#538 (see https://fiona.groups.io/g/main/topic/75506516#60 for comments).

Steps to reproduce the problem.

conda create --name test python gdal fiona # this installs gdal 3.0.2 and fiona 1.8.13.post1
conda activate test
python
>>> import fiona.transform
>>> fiona.transform.transform("epsg:4326", "epsg:3857", [-75.71], [38.06])
([4236819.819591993], [-13244913.18166699])

If I switch the lat/lon position then I get the correct result (http://epsg.io/transform#s_srs=4326&t_srs=3857&x=-75.7169053&y=38.0624956):

>>> fiona.transform.transform("epsg:4326", "epsg:3857", [38.06], [-75.71])
([-8427998.647958742], [4587905.271362515])

If I instead do the conda install with a gdal version less than 3 I get the expected result:

conda create --name test2 python "gdal<3" fiona # this installs gdal 2.3.3 and fiona 1.8.4
conda activate test2
python
>>> fiona.transform.transform("epsg:4326", "epsg:3857", [-75.71], [38.06])
([-8427998.647958742], [4587905.27136252])

Operating system

I have tested this with conda on Windows 10 and Ubuntu 18.04.

Fiona and GDAL version and provenance

@snorfalorpagus has reproduced with different versions on Travis - https://travis-ci.org/github/snorfalorpagus/Fiona/builds/708143904.

[sgillies]

Thanks for the report @calebrob6 . In another issue I'm recommending that users switch, if they can, to "OGC:CRS84" with GDAL 3 instead of expecting the old defaults for "EPSG:4326". But that doesn't mean that we won't have to do something about this.

[ungarj]

I also observed an odd behavior using fiona.transform.transform_geom() with either providing CRSes as string or as rasterio.crs.CRS:

#!/usr/bin/env python
from fiona.transform import transform_geom
from rasterio.crs import CRS
from shapely import wkt
from shapely.geometry import mapping

example_point = mapping(wkt.loads("POINT (289318.0739578609 378154.7763680807)"))
src_crs = "EPSG:31287"
dst_crs = "OGC:CRS84"

# output should be {'type': 'Point', 'coordinates': (11.868736780148138, 47.29350228983309)}

print(transform_geom(src_crs, dst_crs, example_point))

print(transform_geom(CRS.from_user_input(src_crs).to_dict(), CRS.from_user_input(dst_crs).to_dict(), example_point))

Output using GDAL 2.4.4, PROJ 5.2.0, pyproj 1.9.6 looks fine:

{'type': 'Point', 'coordinates': (11.868736780148138, 47.29350228983309)}
{'type': 'Point', 'coordinates': (11.868736780148138, 47.29350228983309)}

However, the output using GDAL 3.0.4, PROJ 6.3.2 and 7.1.0, pyproj 1.9.6 and 2.6.1.post1 swaps the axis on the fiona output not using rasterio.crs.CRS:

{'type': 'Point', 'coordinates': (13.048008632586706, 46.503227029929064)}
{'type': 'Point', 'coordinates': (11.868736773665933, 47.2935022723449)}

When setting dst_crs to EPSG:4326 on the latter the axes are swapped but still the coordinates are not correct:

{'type': 'Point', 'coordinates': (46.503227029929064, 13.048008632586706)}
{'type': 'Point', 'coordinates': (11.868736773665933, 47.2935022723449)}

I was using rasterio 1.1.4 and Fiona 1.8.13.post1 for this, both built from source.