[GRASS5] Temporal data in GRASS?

Markus Neteler neteler at itc.it
Thu Oct 25 07:06:38 EDT 2001

Hi Carl,

On Wed, Oct 24, 2001 at 11:44:10AM -0400, Carl Worth wrote:
> Greetings,
> I'm interested in working with some GIS data that has a rather dynamic
> temporal element. For example, I plan to record the location of
> various moving objects, (via GPS), and later I'd like to replay this
> data in GRASS.
> I've considered doing something as simple as storing timestamped data
> in a database and looping through the query results, displaying
> successive images. But, I wonder if a more integrated solution might
> not be more desirable.
> >From what I've seen so far, I haven't seen anything in GRASS that
> deals with temporal data. (But I am a total newbie to GIS and GRASS so
> I may have missed something obvious, just let me know.) I can imagine
> many applications that have temporal elements, (ie. changes with
> seasons, or from year to year). How have users of GRASS typically
> dealt with these kinds of data?

well, currently only two modules are present

The sites (point data) format also support timestamps. 

Then the "xganim" module allows to play selected raster maps as 
film sequence (note, just fixed in CVS).

> If the current GRASS support isn't sufficient for what I need, then I
> plan to implement whatever it takes. I'm an experienced C programmer,
> and there are a couple of projects here at ISI that could benefit
> from this. I would be interested to hear suggestions from more
> experienced GRASS developers on what the right approach might be to
> incorporate this into GRASS.

This sounds very good. We are quite interested to fully support
timestamps in GRASS. A suggestion could be to extend i.group
(or develop a new module) to group maps according to timestamps
for later analysis, display or whatever.

Here at ITC we intend to improve the multitemporal image processing
features, but a general implementation would be the best. GRASS 5
provides a DateTime library, most (all?) required functions should
be available on library level. Now it is time to extend the
appropriate GRASS modules.

Have a look at the Programmer's Manual to read about the DateTime.

Please let us know your needs.

I would appreciate a collaboration,

best regards

 Markus Neteler

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