GMT Data Server Administration

Cache data and scripts for managing the GMT data server

Current master server is: gmtserver.soest.hawaii.edu, in directory /export/gmtserver/gmt/data

The actual URL is: www.soest.hawaii.edu/gmt/data [you cannot browse there]

Master data server URL: https://oceania.generic-mapping-tools.org

To clone this repo you can run

git clone https://github.com/GenericMappingTools/gmtserver-admin

Cache files

GMT Core developers can add, modify or remove cache files from their working copy of the gmtserver-admin repo, and after merging the gmt server will automatically update its working copy via the crontab script that runs every hour, and if there are changes the gmt_hash_server.txt file will be rebuilt as needed.

Global grids

For now, all Earth and planetary grids are maintained and updated manually. The production of global grids are based on recipes in the recipes folder and can be activated via the Makefile. For new data, design a new recipe. Assuming recipe bugs are worked out, convert the single high-resolution grid or image to our tiled system via scripts/srv_downsampler.sh neptune_relief. Once successful, tile the downsampled grids via scripts/srv_tiler.sh neptune_relief. If these are satisfactory they can be moved to the candidate server. E.g., make place-neptune-relief. If after testing we wish to release this data, run make server-release.

Crontab

The working directory on the gmtserver is updated once an hour via a crontab script running under local account pwessel with this crontab entry:

0 * * * *      /export/gmtserver/gmt/gmtserver-admin/scripts/srv_git_update.sh > /export/gmtserver/gmt/LOGS/git_update.cron.log 2>&1

Downsampling

Here are technical details on how we perform down-sampling. We are filtering, say, the orange 15s data nodes to make a 30s grid (red squares). At each output node we imagine a circle (the small black and three gray for nearby nodes). We use 2 times sqrt(2) times the output increment in degrees (converted to km) which gives us the diameter, i.e., the full filter width expected by grdfilter. Because of this wider circle diameter that touches or includes neighboring output nodes we assure we have no aliasing and all data points contribute to the filtered output. Note: R_p is the planetary radius and Delta is the output grid spacing.

With this scheme, we get a filter width versus output grid spacing that looks like this:

If we look at what the filter weights are for the Gaussian filter along a cross-section through two neighbor nodes we get this: