[gdal-dev] gdal_polygonize.py TIF to JSON performance

[Jukka Rahkonen]

Graeme B. Bell <grb <at> skogoglandskap.no> writes:


> It would be great if the people behind gdal_polygonise could put some
thought into this extremely common
> situation for anyone working with country or continent scale rasters to
make sure that it is handled well.
> It has certainly affected us a great deal when working with data at up to
2m resolution for a country larger
> than the UK...

This really feels like the old "how to eat an elephant problem" and you have
answered already by implementing your 'rbuild' system. It seems to be an
enhanced version of the traditional solution "one bite at a time" because it
can make many parallel bites at a time. I would call it something like "The
Piranha Polygonizer (TM)". By the Jungle Software, Inc. It sounds good, doesn't?

Analogous problem is making point in polygon queries from huge polygons and
this document by Alessandro Furieri has a nice coloured picture about it
http://www.gaia-gis.it/spatialite-3.0.0-BETA1/WorldBorders.pdf.

So the question is who is the first to make a piranha version of
gdal_polygonize.py which takes tile size and perhaps number of thread as
input parameters. The default output could be one polygon file for each
raster tile because for many use cases it would be just perfect. Combining
vector tiles later and making unions of adjacent polygons with same
attribute values feels trivial and fast. But this is a non-programmers
opinion only.

-Jukka Rahkonen-