[GRASS-dev] Principle G3D library question

[Glynn Clements]

Soeren Gebbert wrote:

> What kind of coordinate system should be used in the g3d library?

Make it match the 2d raster library. Row zero should be north; in the
library, in the modules, in the file format, and in terms of
externally-visible behaviour. E.g. this:

> r3.mapcalc --o expr="volume_map = row()"

> #: r3.out.ascii volume_map dp=0

> 8 8 8 8 8 8 8 8 8 8 8 8
> 7 7 7 7 7 7 7 7 7 7 7 7
> 6 6 6 6 6 6 6 6 6 6 6 6

shouldn't happen.

Modules should scan from north to south, i.e. increasing row numbers.

Don't worry too much about compatibility; for 7.0, sanity comes first.

However: if the existing file format has row zero at the southern
edge, then we should to be able to distinguish the new format from the
old, and the library should be able to (transparently) read either (it
doesn't necessarily need to be able to write the old format).

-- 
Glynn Clements <glynn at gclements.plus.com>