topic Re: st_envelope on points in Data Management Questions

st_envelope on points

ModyBuchbinder — Tue, 29 Apr 2014 10:48:33 GMT

Hello all

We are trying to populate a polygon st_geometry layer with envelopes from a few other layers.
Using something like this:
insert into polyLayer (objectid,shape) values (1,(select sde.st_envelope(shape)from pointLayer) );
The docs say that the tolerance will be used to create a valid envelope.
It looks like the created envelope is smaller than the tolerance (we use meter coordinate system with 0.001 tolerance).
The result layer cannot be edit and have a few other problems but it can be drown without errors.
Is anybody out there is doing any similar process?

Thanks
Mody

Re: st_envelope on points

VinceAngelo — Tue, 29 Apr 2014 12:28:31 GMT

That SQL statement is quite odd. Is there only one feature in pointLayer?

Providing specific details about the coordinate system, coordref X/Y scale, the coordinate
value in the point layer, and the coordinates in the resulting polygon would be necessary
before we could provide any assistance.

- V

Re: st_envelope on points

ModyBuchbinder — Tue, 29 Apr 2014 12:40:15 GMT

Hi Vince

You are right �?? I dropped the WHERE statement. In real life we use next_rowid to get the OBJECTID.
We use ITM (Israel TM Grid) projection. The default tolerance is 0.001, the resolution is 0.0001
Measure of the result envelope gives 0.0004 from side to side instead of 0.002. The length is 0.0016 (0.0004 * 4) �?? it should be 0.004 (0.001 * 4)

Thanks
Mody

Re: st_envelope on points

VinceAngelo — Tue, 29 Apr 2014 12:58:35 GMT

It appears the documentation is incorrect, though even a square millimeter is way too
small to represent a point on a map (I'd think ten meters would be more appropriate).
If you buffered the point and took the envelope of that you could control the size of the
resulting squares.

- V

Re: st_envelope on points

ModyBuchbinder — Tue, 29 Apr 2014 13:19:16 GMT

Yes, we already implmented the buffer.
The doc's are wrong and even if the software would work by the docs it would not make too much sense...

Mody