[GRASS-user] Projection Units and Values Negatively Affect r.topidx Results

[Rich Shepard]

On Thu, 18 Feb 2010, Hamish wrote:

> try switching to grass 6.5 for a minute, and running r.proj -p and or -g.
> The output of -g can be pasted directly into g.region, and then it is an
> easy 'g.region -p', 'g.region res= -ap' to clean it up. It is a real
> breath of fresh air after all the quiting & restarting grass + v.in.region
> tricks, although that is still a nice check to do.

Hamish,

   Wow! After all of yesterday's anguish, 6.5's r.proj did the trick. That's
teriffic! So, should I continue this project in 6.5 or revert to the 6.4
revision 41119?

> check that the PROJ_UNITS in your source location is valid.

   Yes: they're in English units and the destination units are metric.

> do not expect coords to be the same, they start off counting from 0,0
> somewhere far off to the south west and cover a different number of units
> to get to Oregon based on their length.

   Besides this, the bounds of the source location are in feet while the
bounds of the destination location are in meters. Different numbers and
different magnitudes.

   Now to reproject all source data and re-do all the project-specific data.
Well, there goes the weekend, but at least I know the numbers and analyses
are correct if this case ever goes to trial and the plaintiff's attorney
challenges my analytical methods, results, and interpretations.

Many thanks again,

Rich