[GRASS-user] d.rast.edit does not save edited cells (?)

[Glynn Clements]

Nikos Alexandris wrote:

> > > And another question: Is it possible to ad something else besides an
> > > Aspect map? Use maybe transparencyt and a background command (like with
> > > r.digit)? What are the limitations?
> > 
> > I'm not sure how a background map could work; it would be obscured by
> > the map being edited.
> > 
> > The aspect map feature was only added because it was present in the
> > original d.rast.edit module which the script replaces. I have no idea
> > what purpose it serves.
> 
> It makes (some) sense for me. I was and still am doing  a lot of visual
> interpretation (currently upon MODIS imagery).
> 
> I need to collect samples for i.smap for example and with MODIS (MOD09,
> 250m pix.res) this task is a challenge. And I am not only digitising
> samples from the scratch, but I use also some classes (e.g. Urban) from
> valid existing land cover maps. Yet, I need to correct the borders for
> some of these Urban areas.
> 
> From this perspective all kinds of "ancillary" data are useful.

I'm not doubting the utility of a background map, I'm just not sure
how it would be implemented.

> Aspect
> helped me to identify some flat areas in agricultural zones (it is
> expected that flat areas have "one" common aspect... no?).

It depends what you mean by "flat". A common aspect implies zero
curvature rather than zero gradient. Exactly horizontal areas have an
undefined aspect (the direction of steepest slope isn't meaningful if
there is no slope). Areas which are roughly horizontal tend to have
essentially random aspect.

> It would be
> even more useful if DEM values (pure numbers) could be visualized (like
> "add cell values layer") or any kind of values from a thematic map.

It would be easy enough to add additional information, e.g. numbers. I
suppose that editing a map displayed as numbers over a background
of filled rectangles would be feasible, as would the converse.

But if the both the foreground and background consist of filled
rectangles, you are only going to be able see one of them.

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