[GRASS-dev] Temporal GRASS GIS update

Sören Gebbert soerengebbert at googlemail.com
Thu May 2 02:01:01 PDT 2013

Dear all,
just for your information about the latest developments in grass7 svn:

New temporal modules are available:
t.merge [1] -- to merge several space time datasets into a single dataset
t.shift [2] -- to shift all registered maps of a space time dataset by a
temporal increment (seconds, minutes, days, months, years)
t.snap [3] -- to snap the time stamps in a space time dataset

I have modified the GRASS GIS temporal framework to support a command
history for space time datasets. The command history will be shown if you
use t.info to print information's about space time datasets. There are
several modules that create new datasets and there are several modules that
modify them (t.register, t.unregister, t.merge, t.shift, t.snap, t.rename,
t.support). Hence there may be more than one command in the stds history.
I needed to add new columns to the temporal database to implement the
command history. Existing locations with temporal databases should be
automatically updated when a temporal command is executed. New locations
and new mapsets will have the new columns automatically.

I have changed the default temporal database path from
"location/PERMANENT/tgis.db" to "location/PERMANENT/tgis/sqlite.db".
ATTENTION: The new path will also be used when you create a new mapset in
an existing location. Hence you need to set the path with t.connect to
point to the old default path "location/PERMANENT/tgis.db" in case you
don't want to have two separate temporal databases.

A spatio-temporal topology builder is now available to build
spatio-temporal topology connections between map objects for 1D, 3D and 4D
extents. The topology creation is based on the R*Tree implementation in the
vector library that was modified by Markus Metz (many thanks Markus!!!!) to
support 4D extents. We will make use of this in the GSoC Spatio-temporal
algebra project.
While implementing this i needed to modify the database structure a bit, so
that temporal modules that access older temporal databases will produce
warnings. You can ignore them since i have implemented a (slow) work around
for older databases.

I have restructured the temporal library in lib/python/temporal and
lib/temporal/SQL and added more doxygen documentation.

That's all, i hope i did not broke anything. :)

Best regards

[1] http://grass.osgeo.org/grass70/manuals/t.merge.html
[2] http://grass.osgeo.org/grass70/manuals/t.shift.html
[3] http://grass.osgeo.org/grass70/manuals/t.snap.html
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