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

[Sandro Santilli]

On Tue, Feb 12, 2013 at 01:43:24AM +1000, Egil Möller wrote:
> Is there any way postgis could work around this?

Not fast ones.
I guess you could re-add M by looking at the original points and set
M from matching or interpolating points.
It would be nice to have a C level function for this.
Maybe a permutation on this on:
http://www.postgis.net/docs/manual-2.0/ST_AddMeasure.html

> From a user pefspective
> this seems like a very arbitrary restriction (and it's entierly
> undocumented).

True.

> Are there any other such "traps" for the M (and/or Z) coordinate?

I'm sure there are a lot of M traps.
The documentation should have a "support Z" label for functions but
I see, for example, that it isn't even used for ST_Simplify.
Patches against documentation are welcome.

--strk;