Geonode -> Django 2.2 x GDAL 3

[cmotadev]

Hi @afabiani and other colleagues

We are developing a plugin for GeoNode, running on Docker, that uses geonode-project and we are experiencing some issues. We have a django model that uses a GeometryField and the model saves geometry with flipped coordinates.

I checked that Geonode uses Django 2.2.x, which GDAL requirements are up to 2.3.x, and in the dockerfile it brings GDAL 3. I think it's a Django behavior than Geonode itself, but I think that it's crucial for setting the geonode requierements - GDAL 3 changed the default behavior of coordinate transformation

There is a ticket into the Django Project that issues this problem.

My suggestion is to put GDAL 2.X as default, or adopt Django 3.1.x as default, which one is easier :)

Thanks for appreciate.

Expected Behavior

GeoDjango saves the geometry as is

Actual Behavior

GeoDjango is flipping the geometry's coordinates

Steps to Reproduce the Problem

1. Create a Django geonode project
2. Create a spatial model using geodjango
3. Fill the model props and save it to db.

Specifications

• GeoNode version: 3.2.1
• Installation method (manual, GeoNode Docker, SPCGeoNode Docker): GeoNode Docker
• Platform: Linux
• Additional details:

[afabiani]

@cmotadev currently only master is using Django==3.2.* the older branches are still using Django 2.*

As far as I remember we used this checks in order to deal with the GDAL 3 coordinate flipping issue

https://github.com/GeoNode/geonode/blob/3.2.x/geonode/utils.py#L398

Maybe this one could work for you too?

[cmotadev]

@afabiani I checked your suggestion and doesn't work for me, but your implementation gived me an idea: The main problem is because the GeoDjango implementation doesn't use pyGDAL. The bindings are done directly on the library.

I solved my problem subclassing the GeometryField to flip coordinates before saving into DB and after retrieve on it. I used Shapely to make the things easier.

# models.py
from django.contrib.gis.db.models import MultiPolygonField as BaseMultiPolygonField
from django.contrib.gis.geos import GEOSGeometry
from django.db import models
from osgeo.gdal import __version__ as version 
from shapely.wkb import loads
from shapely.ops import transform


class MultiPolygonField(BaseMultiPolygonField):
    gdal_version = int(version.split(".")[0])

    def _fix_gdal_axis_error(self, geom):
        if self.gdal_version >= 3:
            _g = transform(lambda x, y: (y, x), loads(bytes(geom.wkb)))
            wkb = _g.wkb_hex
            srid = geom.srs.srid
        
            geom = GEOSGeometry(wkb, srid=srid)
        
        return geom
    
    def to_python(self, value):
        _value = super().to_python(value)
        return self._fix_gdal_axis_error(_value)

    def from_db_value(self, value, expression, connection):
        if value is None:
            return value

        return self._fix_gdal_axis_error(value)

# Create your models here.
class SpatialModel(models.Model):
    name = models.CharField(
        max_length=255
    )

    shape = MultiPolygonField(
        srid=4674
    )

    def __str__(self):
        return self.name