Add buffer around polygon in meters using GeoDjango

Question

I'm using GeoDjango with PostGIS. I have a table with a polygon field called "geofence".

I want to add a 5m buffer zone around the polygon.

obj.geofence.buffer(5)

This results in a huge buffer zone though. Experimentally it looks like the buffer zone is around 500km wide.

It appears that I must somehow do a transformation of my meter unit to the system used by polygon.buffer. How can I do that?

Answer 1

Which SRID are you using?

If you are using WGS84, Try this:

distance = 5 # distance in meter
buffer_width = distance / 40000000.0 * 360.0
buffered = obj.geofence.buffer(buffer_width)

Source: https://stackoverflow.com/questions/31940674/optimal-query-in-geodjango-postgis-for-locations-within-a-distance-in-meters