[gdal-dev] Check validity of geometries before writing them into vector tiles?

[Rahkonen Jukka (MML)]

Even Rouault wrote:

> Perhaps you could play with the SIMPLIFICATION and SIMPLIFICATION_MAX_ZOOM options ?
Sure, as I wrote I admit that my test did not make much sense, but trying things before reading the manual sometimes reveals something interesting.  

> Perhaps you should also use an already simplified layer for the lowest zoom level (see the CONF option)
For sure yes, coordinate space of 4096x4096 is far too small for this dataset.

> Are you sure you get polygons with less than 4 points ? Normally they should be discarded.
Quite sure yes by looking at what the ST_IsValidReason from the SQLite dialect prints 
ST_IsValidReason(geometry) (String) = Invalid: Toxic Geometry ... too few points

There are other variants of invalid geometries and actually a few valid as well. Here is one example with an invalid component

  MULTIPOLYGON (((516384 6815744,516384 6815744,532768 6815744,516384 6815744)),
((516384 6815744,516384 6815744)),((516384 6815744,516384 6815744)))

My zero tile is here http://www.latuviitta.org/downloads/0.pbf

-Jukka Rahkonen-