[GRASS-dev] Request to add a GCP file in vector directories

[Glynn Clements]

Hamish wrote:

> > This is a good point. Should a generic gcp file just be stored in
> > PERMANENT? What about maps with different extents--especially
> > non-overlapping maps--in the same location?
> 
> I'm not a fan.
> 
> e.g. I've got a mapset:
> 
> grassdata/simple_xy/charts/
> 
> where I have scanned versions of nautical charts imported.
> 
> For each new chart I have it's own group with its own GCP info.
> 
> I don't want a new mapset, let alone location, for each new scan.

Right. It depends largely on whether the location is being used as a
general purpose container or like a normal (georeferenced) location
except that it has a non-standard projection.

Even in the latter case, you might need multiple transformations, as
one which is a good fit for one map might not be a good fit for
another. Producing a transformation which is a good fit for the entire
location would be difficult if you can only set reference points over
a single map.

Support for locations with user-defined (polynomial) projections would
need to be in addition to the existing transformation tools, not a
replacement. But it may be worth considering at this point.

> The group thing is good logically & works well in practice.
> Again I'd suggest we keep using the same method, just make a nice
> front end for it which merges and hides the gritty details.
> (I can picture a tabbed GUI with target in one, registed maps in
> another, etc..)

Command-line front-ends for some of the tools would also be nice.

[By "command-line", I mean input via command-line options and/or
files/stdin, rather than via curses forms.]

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