Opened 5 years ago

Last modified 5 years ago

#15165 assigned Bug

GeoQuerySet.perimeter returns invalid results on geometry fields with geodetic coordinate systems

Reported by: jbronn Owned by: jbronn
Component: GIS Version: 1.2
Severity: Normal Keywords: perimeter
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

The method GeoQuerySet.perimeter returns Distance objects with erroneous values when called on a geometry field that has a geodetic coordinate system (e.g., srid=4326). The values in the returned distance objects are really perimeter measurements in degrees of latitude/longitude, rather than meters.

Here's an example using the models and data from the GeoDjango tutorial:

>>> from world.models import WorldBorders
>>> us = WorldBorders.objects.perimeter().get(name='United States')
>>> print us.perimeter
771.493229562 m

Obviously, the perimeter of the United States is greater than a kilometer. To fix, the helper method GeoQuerySet._distance_attribute needs to be modified to raise an exception or return a raw numeric value when attempting to calculate perimeters on geodetic coordinate systems.

Change History (5)

comment:1 Changed 5 years ago by jbronn

  • Needs documentation unset
  • Needs tests unset
  • Owner changed from nobody to jbronn
  • Patch needs improvement unset
  • Status changed from new to assigned

comment:2 Changed 5 years ago by russellm

  • Triage Stage changed from Unreviewed to Accepted

comment:3 Changed 4 years ago by lrekucki

  • Severity set to Normal
  • Type set to Bug

comment:4 Changed 3 years ago by aaugustin

  • UI/UX unset

Change UI/UX from NULL to False.

comment:5 Changed 3 years ago by aaugustin

  • Easy pickings unset

Change Easy pickings from NULL to False.

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