[postgis-users] ST_SimplifyPreserveTopology and ST_Simplify does not preserve measures

[Egil Möller]

POSTGIS="1.4.0" GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.7.1, 23 September
2009" USE_STATS

So yes, this is an older system. If it works fine in a newer version I
guess I should consider the issue closed :)

On 02/08/2013 01:37 AM, Nicolas Ribot wrote:
> By the way, wich Pgis version ?
>
> On  POSTGIS="2.0.2 r10789" , it gives correct result:
>
> select st_astext(st_simplify('LINESTRINGM(0 0 0, 1 1 1, 10 10
> 10)'::geometry, 1));
>            st_astext           
> -------------------------------
>  LINESTRING M (0 0 0,10 10 10)
> (1 row)
>
> Nicolas
>
>
> On 7 February 2013 16:33, Nicolas Ribot <nicolas.ribot at gmail.com
> <mailto:nicolas.ribot at gmail.com>> wrote:
>
>     Sorry, answered to fast... ;)
>     Don't know with it drops M dimension.
>
>
>     On 7 February 2013 16:28, Nicolas Ribot <nicolas.ribot at gmail.com
>     <mailto:nicolas.ribot at gmail.com>> wrote:
>
>         Hi,
>
>         You are simplifying data with a 1000 degrees tolerance !
>         Project your data into a planar system, then simplify it.
>
>         Nicolas
>
>
>         On 7 February 2013 15:59, Egil Möller <egil at skytruth.org
>         <mailto:egil at skytruth.org>> wrote:
>
>             It seems like ST_SimplifyPreserveTopology and ST_Simplify
>             does not
>             preserve measure coordinates and mangles my linestringm to
>             an ordinary
>             linestring. Why is that? It seems like a rather random
>             limitation!
>
>             mydb=> select ST_AsEWKT(line) from ais_path limit 1;
>              SRID=4326;LINESTRINGM(102.647916667 5.63022166667
>             1357100014,102.647916667 5.63022166667 1357446366)
>
>             mydb=> select ST_AsEWKT(ST_SimplifyPreserveTopology(line,
>             1000)) from
>             ais_path limit 1;
>              SRID=4326;LINESTRING(102.647916667
>             5.63022166667,102.647916667
>             5.63022166667)
>
>             Best regards,
>             Egil
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>
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