[postgis-users] Topology: Simplifying Coastlines with Islands

[Sandro Santilli]

On Fri, May 25, 2012 at 11:15:09PM +0200, Michiel J. van Heek wrote:

> These are the warnings for edge 11652, the coastline of Norway (on
> the screenshot in my previous post):
> 
> WARNING:  Simplification of edge 11652 with tolerance 0.5 failed:
> SQL/MM Spatial exception - geometry crosses an edge
> WARNING:  Simplification of edge 11652 with tolerance 0.25 failed:
> SQL/MM Spatial exception - curve not simple
...
> 
> The "curve not simple" makes we want to try your suggestion to use
> ST_SimplifyPreserveTopology instead of ST_Simplify. I will try that
> tomorrow (it is late in my timezone) and let you know the outcome.

Yeah, it might work at 0.25 :)

> The ticket you mentioned seems to be about creating topology from
> geometry. That part - SELECT CreateTopology('countries_topology',
> 4326) - ran flawless in my case. (Long, but without errors.) The
> ticket is not about simplifying topology, or is it?

I considered it generally about error messages. The first one above,
for example, might be more useful if it told you _which_ edge was
the simplified edge crossing, and maybe even _where_...


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