[GRASS-user] Large Grass Raster Notes

[Jeshua Lacock]

Greetings,

In the event my experience working with rather large GRASS rasters may be useful, I thought I would share it. The following notes were compiled running the  GRASS 7.0.0beta4-141230 package on Mac OS X 10.10.1. The system is a 6-core Xeon with 32GB of RAM, running in full 64-bit mode.

1. Using an r.external virtual mosaic as the input proved impossible trying to run r.resample on it on trying to produce a nearly teracell raster (I ended up breaking sub-tiles). I closely followed the instructions on the Wiki.

2. On smaller sub-tiles of said image, r.resample was insanely slow even with the external imagery. At first I thought it was a limitation of being overwhelmed with small sector requests and purchased a terabyte SSD, copied the external imagery to the SSD, but that didn’t noticeably help. Throughput was way less than 1mb/sec.

3. g.remove is unusable for long lists. Actually applies to I think any utility that takes a list for input. I wish I could just put it to a file so it could parse it line by line (As I understand the issue it is a limitation of the insanely long shell arguments).

If anyone wants me to elaborate on anything, or has pointers how to do things better - please let me know!


Cheers,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171