[Geojson] coordinate order

Martin Daly martin.daly at cadcorp.com
Sun Mar 9 12:02:08 PDT 2008

> On Sun, Mar 09, 2008 at 12:34:00PM +0000, Martin Daly wrote:
>> For completeness should we also add:
>> "coordinate_direction": [1,-1]
>> or similar? That would allow south, west and down positive ordinates.
>> Some country-specific (mostly projected) CRS-s are like this.
> How would a client use this information? Would OpenLayers somehow flip
> the display so that down was up?
> I don't know how people use things like this: using OpenLayers and
> GeoServer as examples, how would this change the behavior of drawing,
> for example, a line on top of a map tile?

Sorry, I didn't explain myself very clearly.

What I mean is that, as before, all coordinates will be in easting  
then northing direction: just as they are in easting then northing  
order.  A coordinate_direction array would be present if one or more  
of the axes had the opposite direction.

For example, an Australian CRS might choose to have all +ve values in  
the Y (latitude) axis, i.e. southings instead of northings.  In a  
GeoJSON geometry the coordinates would always be -ve because, as with  
axes order, that is (or becomes) fixed. A simple client would be fine,  
as with the axes order.  A more advanced client could look at  
coordinate_order *and* coordinate_direction in order to re-jig the  
coordinates to fit the CRS definition.

The coordinate_direction array would contain "1" for no direction  
change, and "-1" to negate.  No other values would be allowed.


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