[postgis-users] ST_Union (8.4) and TopologyException

[Simon Greener]

Robert,

Thanks for responding.

>> I have had to use ST_Transform as I have found the query even more
>> problematic when run against the original geodetic data.
>
> Projections are a very likely cause of topology errors for accurate data...
> how was it more problematic for geodetic data - more topology errors?
>
> Does:
>
> SELECT count(*) FROM mytable WHERE (geom IS NOT NULL) AND (NOT
> st_isvalid(st_transform(geom,
> 96687)));
>
> return anything for either of the tables?

Returns True for both tables. So the projection is not, necessarily, the cause.

regards
Simon
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