[GRASS5] Temporal data in GRASS?

Roger Bivand Roger.Bivand at nhh.no
Thu Oct 25 15:44:06 EDT 2001

On Thu, 25 Oct 2001, Carl Worth wrote:

> Markus and Helena,
> Thanks for your quick feedback -- I think it will be very helpful.
> Thanks for the pointers to the DateTime library. It's exactly what I
> was hoping for, (a data structure with either absolute or relative
> time values). The TimeStamp structure is also exactly what I had hoped
> it would be, (either a point time or a range).
> To summarize, it sounds like the database has slots for TimeStamps in
> several places, but that support could be extended in several
> places. Also, the ability to query/organize data based on time, and to
> display the time seems to be missing. I'll take it on myself to start
> improving these areas.
I'm sure many of us will find this useful! A concern that I have is that
there are different time/date standards (in operating systems, in database
systems, POSIX, etc.). There is a very good survey in:

  author       = {Brian D. Ripley and Kurt Hornik},
  title        = {Date-Time Classes},
  journal      = {R News},
  year         = 2001,
  volume       = 1,
  number       = 2,
  pages        = {8--11},
  month        = {June},
  url          = {http://CRAN.R-project.org/doc/Rnews/},

(that's R-News of the R data analysis community) which may help in
revisiting the code in GRASS. The R code may also be useful in seeing how
to match different systems' assumptions about time through the autoconf
system for compilation. In addition, the R code is GPL, so maybe some of
it may be of direct use - R-1.3.1/src/main/datetime.c makes interesting
reading, and is more up-to-date (I feel) than what you see in
src/libes/datetime/. Certainly the discussion in R-News seems based on
hard-won experience!


Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no
and: Department of Geography and Regional Development, University of
Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.

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