[postgis-users] creating a spatial table with 2 rows

[Jan Hartmann]

Heiko,

If your table has x and y fields (reals) but doesn't have a geometry 
field yet, add this with:

SELECT AddGeometryColumn ('<database>','<table>',the_geom,<SRID>,'POINT',2);
(See http://postgis.refractions.net/docs/x314.html#AEN384)

Update the geometry field with the values from the x and y fields:

UPDATE <table> SET the_geom = GeometryFromText
     ( 'POINT(' || x::text || ' ' || y::text || ')' ,<SRID>);

The GeometryFromText function takes a string as first parameter (e.g. 
'POINT(12.45 45.90)'. You can use this if your coordinates are in an 
external ASCII file.
(See: http://postgis.refractions.net/docs/x398.html#AEN401).
When the coordinates are already in the table as numbers, they can be 
cast to strings with the cast operator ( :: ) and concatenated with the 
concatenation operator ( || ). This concatenated string can be used as 
input for GeometryFromText. (Perhaps this could be added as an example 
to the docs?)

You can use SRID=4326 for latlon coordinates.

Regards,

Jan Hartmann

Heiko Kehlenbrink wrote:
> Hi all,
> 
> having a little problem creating a spatial table.
> I've got a table with 1 row for x and y coordinates each.(geographical 
> coords).
> What would be the easiest way to get these rows known by postgis as 
> spatial informations?
> 
> btw
> what would be the srid for geographical coordinates?
> 
> best regards
> 
> heiko
> 
> 
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Jan Hartmann
Department of Geography
University of Amsterdam
jhart at frw.uva.nl