The [http://code.djangoproject.com/browser/django/branches/gis gis] branch intends to add a contrib app implementing geographic support.

= What's GIS? =
 * [http://cfis.savagexi.com/articles/category/gis Series of blog posts] giving intro to GIS; choice quote from [http://cfis.savagexi.com/articles/2006/04/20/on-coordinate-systems#comments an early post]: "If you feel like ending a conversation with a developer then simply bring up the topic of character encodings ... [o]r ... coordinate systems. ... So in the spirit of Tim Bray's and Joel Spolsky's wonderful writeups of character encodings, I thought I'd put together a basic survival guide to coordinate systems over my next few posts and then tie it back to Google Maps."
 * More on [http://en.wikipedia.org/wiki/Map_projection map projections], including why people can't agree on just one (utf-8).

= Useful code =
 * [http://postgis.refractions.net/ PostGIS], the [http://www.opengis.org/docs/99-049.pdf OpenGIS SQL Types (pdf)] implementation for Postgresql
 * [http://geos.refractions.net/ GEOS], low-level C++ port of [http://www.jump-project.org/project.php?PID=JTS Jave Topology Suite], used by PostGIS
   * [http://zcologia.com/news/14/python-geos-module/ PyGEOS, now outdated due to PCL, below], and shedloads more stuff on "python, geospatial, and the web"
   * [http://gispython.org/ Python Cartographic Library] - [http://trac.gispython.org/projects/PCL actively maintained], huge GIS package, GPL.
 * [http://exogen.case.edu/projects/geopy/ Geopy] calcs distances using (very accurate) [http://www.movable-type.co.uk/scripts/LatLongVincenty.html Vincenty], and uses the [http://en.wikipedia.org/wiki/World_Geodetic_System WGS 84] datum by default.  Also has utility functions for UOM conversions.


= Questions =
 * When dealing with points (say, degrees) from, do they need to be converted to be useful on the back-end data, assuming -that- data is in degrees?  Is it enough to have the same datum and origin?  (Reading the intro above is likely to answer the question.)

= Implementation =

== Phase 1 ==
  Assume existing data and columns, and that the UOM given is same as backing data.
  Support a custom manager (and queryset) to support lookups.

=== GeoTypes ===
  GeoTypes supports only psycopg1, which is dead.  Porting it to Psycopg2 doesn't look too terrible.  Upside is conversion from type params to SQL.  Simplifies (avoids?) QuerySet modification.

=== Geos ===
  I'm not sure how we can use GEOS without also doing something like GeoTypes down in the QuerySet.  Ideas?

{{{

Schools.objects.geo_near(point=x, radius=1.0)
Schools.objects.geo_within(bound_box=box)
}}}


== Phase 2 ==
=== Field Types ===
 * To allow update through ORM, new fieldtypes would be needed.


=== GIS utilities ===
wrapper for geos, have the ability to do something like

{{{
from django.contrib.gis import area
area(bbox.geom)
}}}