[gdal-dev] Buffer unit

[Jukka Rahkonen]

Jaak Laineste (Nutiteq <jaak <at> nutiteq.com> writes:

 
> Isn't there really better solution than dual-transformation? The problem
with this is that you need pick a
> projection wisely, and there is no global projection what you can use
without having big distortions
> nearer to poles (in the case of Mercator for example. You need to use
projection depending on particular
> location, and even then you would have transformation errors.
> 
> Root problem is that most JTS/GEOS, including buffer() implementations can
do cartesian math only. Good
> solution would be to implement buffer function from latitude/longitude
directly, say
> buffer(lat,lon,buffer_meters).  Any takers?

I do not understand much about these things and I mainly wanted to
demonstrate that what can be done in PostGIS is ofter possible to do without
PostGIS by using GDAL and the SQLite/Spatialite dialect.

I feel that first steps towards what Jaak wil have has been taken in PostGIS
with the LWGEOM function ST_Project 
http://postgis.net/docs/manual-2.1/ST_Project.html
The same function is also available in Spatialite 4.1
http://www.gaia-gis.it/gaia-sins/spatialite-sql-4.1.0.html and in GDAL
through OGR SQLite dialect.

What seems to be is missing is calculating the right azimuths for offsetting
vertices and smuggling the code inside the buffer function.

-Jukka Rahkonen-

> 
> Jaak
>