CODEWITHSUNDEEP
pythonpostgisgeodjango
sdawodu
sdawodu

Reputation: 31

Geodjango- Can't get point in a polygon

I have a model which is based on a shapefile:

My model is: from django.contrib.gis.db import models

class RegionBorder(models.Model):

    region_code = models.CharField(max_length=9)
    region_name = models.CharField(max_length=24)

    mpoly = models.MultiPolygonField(srid=27700)
    objects = models.GeoManager()

    def __str__(self):
        return self.region_name

I've successfully imported the polygons into my database:

len(RegionBorder.objects.all())
9

But when I try to find a point within the polygons, I get nothing back. I know the point must be in the polygon as they're maps of the regions of England and I'm trying to find Nelsons column bang in the middle of London.

p = GEOSGeometry("Point(-0.127907 51.507786)", srid=27700)

RegionBorder.objects.filter(mpoly__contains=p)
[]

What am I doing wrong? I've swapped the co-ordinates just in case I had them the wrong way round, I've removed the srid arguments and started again. This is my first time doing any GIS stuff so I'm completely lost

Upvotes: 1

Views: 960

Answers (1)

sdawodu
sdawodu

Reputation: 31

I set the wrong SRID for the points. Fixed by using srid 4326 for lng/lat points and then transforming to correct projection before search

from django.contrib.gis.geos import GEOSGeometry

p = GEOSGeometry("Point(-0.127907 51.507786)", srid=4326) # 4326 for standard lng/lat coordinates

# Transform to same coordinate system as maps
p.transform(27700)

RegionBorder.objects.filter(mpoly__contains=p)
[<RegionBorder: London>]

Upvotes: 1

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