[postgis-users] ST_StartPoint() for MultiLineStrings

[Paul Ramsey]

This is actually one of those places where I wonder if an
answer-returning approach would be better or not. One interpretation:

ST_StartPoint(MultiLineString) -> MultiPoint

Which implies

ST_ExteriorRing(Multipolygon) -> MultiLineString

All sorts of fun. Question is: is this an improvement... still
requires handling the issues of N > 1, somehow or other.

P.

On Tue, Sep 25, 2012 at 2:08 PM, Paul Ramsey <pramsey at opengeo.org> wrote:
> When ST_NumGeometries == 1, you can run ST_StartPoint on
> ST_GeometryN(geom,1). Where ST_NumGeometries > 1 you are in
> "interpretation land". What's the start point of a geometry with two
> lines?
>
> P.
>
> On Tue, Sep 25, 2012 at 1:38 PM, David Quinn <daithiquinn at gmail.com> wrote:
>> As ST_StartPoint( multilinestring ) returns NULL for PostGIS 2.0
>> (http://postgis.refractions.net/docs/ST_StartPoint.html ), what
>> approach can be used to identify the start and end points of a
>> multilinestring?
>>
>> Thanks,
>> David
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users