Geodjango / SRID for simple Cartesian coordinate systems?

[Evan Reiser]

I'd like to take advantage of Geodjango but my objects only exist in a
Cartesian coordinate system (rather than the surface of a sphere).
Can anyone recommend an SRID to use?

I can imagine that the simple/naive solution would be not to use
GeoDjango and just store the X,Y coordinates as their own columns,
however since its a very large data set i'd like to take advantage of
the spacial indexing

-Evan

[Trevor Wiens]

I'm not sure about the best way to do it, but two possibilities come to mind.

1. I don't know if GeoDjango requires it, but in PostGIS you can have
geometry objects with no SRID declared. I believe however if you do
this PostGIS assumes that the data is SRID 4326 (WGS 84 lon/lat) for
any calculations.

2. The other option would be to use a UTM or TM based projection
assuming the values are within the range of a single zone. This way
any calculations you did, (point in polygon, area, perimeter, etc)
would be based on an x,y grid.

TSW

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Trevor Wiens
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[Robert Coup]

On Fri, Nov 19, 2010 at 12:19 PM, Evan Reiser <evan....@gmail.com> wrote:

I'd like to take advantage of Geodjango but my objects only exist in a
Cartesian coordinate system (rather than the surface of a sphere).
Can anyone recommend an SRID to use?

Try using -1 for your srid value on your field.

Unless you're doing reprojection to convert from/to another coordinate system it actually doesn't matter - the numbers are just treated as numbers within an SRID, so 4326 would even work.

Rob :)