How to transform geometry in django rest framework gis

Question

I am newbie to Django and developing a REST API using Django Rest Framework (DRF) and GIS. Previously, I was using an SQL query for transforming a geometry:

select
    id, 
    name, 
    round(value::numeric, 2) as value,
    st_transform(geometry, 3857) as geometry
from
    my_model

...

class MyModel(models.Model):
    name = models.CharField(max_length=50, blank=True)
    value = models.FloatField()
    geometry = models.GeometryField(null=True, blank=True)


    class Meta:
        db_table = u'my_model'

    def __unicode__(self):
        return '%s' % self.name

Here serializer class:

class MyModelSerializer(serializers.GeoModelSerializer):
    class Meta:
        model = MyModel
        fields = ('id', 'name', 'value', 'geometry')

I have also tried to do this way but cannot transform output

class MyModelViewSet(viewsets.ModelViewSet):

    queryset = MyModel.objects.all().transform(3857)
    serializer_class = MyModelSerializer

How can I do this in Django Rest Framework and GIS? Where can I get query sample or a comprehensive tutorial for DRF?

score 3 · Accepted Answer · answered Mar 20 '14 at 15:11

3

Solved:

Add the srid argument to transform function. I was considering as

transform(srid)

first argument as srid but should be like this

transform(srid=3857)

class MyModelViewSet(viewsets.ModelViewSet):

    queryset = MyModel.objects.all().transform(srid=3857)
    serializer_class = MyModelSerializer

answered Mar 20 '14 at 15:11

Shoaib Ijaz

5,347
12
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84

This gives me: `AttributeError: 'QuerySet' object has no attribute 'transform'` where does function `transform()` comes from? do you have related docs? – Henhuy Nov 17 '20 at 13:34
Maybe, this can help you https://docs.djangoproject.com/en/3.1/ref/contrib/gis/geos/#django.contrib.gis.geos.GEOSGeometry.transform – Shoaib Ijaz Nov 18 '20 at 12:24
https://gis.stackexchange.com/questions/94640/geodjango-transform-not-working – Shoaib Ijaz Nov 18 '20 at 12:24
But as I understand (from here: https://stackoverflow.com/a/48840336/5804947) the `transform()` function has been deprecated and replaced by database function [`Transform`](https://docs.djangoproject.com/en/3.1/ref/contrib/gis/functions/#django.contrib.gis.db.models.functions.Transform), correct? But then I cannot use answer given above as annotations dont work with `GeoModelSerializer` (see my issue https://github.com/openwisp/django-rest-framework-gis/issues/250) – Henhuy Nov 18 '20 at 12:48

Bibhas Debnath · Answer 2 · 2014-03-19T06:46:24.027

2

You can provide a default SRID to your GeometryField -

geometry = models.GeometryField(srid=3857, null=True, blank=True)

And Django will automatically handle the conversion. More details on the doc and tutorial.

Where can i get queries sample or comprehensive tutorial for rest framework gis?

You can find all about geodjango on Django documentation. Django rest framework is noting but Django.

edited Mar 19 '14 at 06:46

answered Mar 19 '14 at 06:41

Bibhas Debnath

14,559
17
68
96

How to transform geometry in django rest framework gis

2 Answers2