[GRASS5] timeseries: null file, r3

[Joel Peter William Pitt]

Hi there,

I need to store many thousands of maps for different model simulation 
runs as each has at least 25 maps in a timeseries.

Currently running 100 replications of a 25 year model on a 2000x2000 
region results in about 2.1 gig.
This on its own is okay, but I need to run sensitivity analyses on a 
range of parameters, meaning each value I test for a parameter gives a 
location of 2.1 gig!

Checking out the actual data files however shows that the cell files are 
only about 60k each. The problem is the uncompressed null bitmasks that 
are 700k each. Now, I can explicitly remove the null bitmask using 
"r.null -r", but I was wondering if the null mask will just get 
automatically created next time I run a GRASS command? Also, I'm under 
the impression that if there is no null bitmask then values equal to 0 
in the cell file are interpreted as nulls, is this right? Is there 
anyway to specify NOT creating a null mask when creating a map?

A while back I suggested using 3d rasters to store timeseries, but I got 
the impression at the time it wasn't very far developed and I knew 
little about GRASS then. Does anyone who knows more about the r3 design 
know if storing a timeseries in this way would be more space efficient? 
The timeseries is a sequence of snapshots of a growing region, so for 
the most part a region in a map at time t+1 will encompass the region in 
a map at time t.

Thanks,
Joel

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Joel Pitt, Room B534
Bio-Protection & Ecology Division
PO Box 84
Lincoln University 8150
New Zealand