[R-sig-Geo] Making web-repository of gridded maps: NetCDF or WKT Raster?
hengl at spatial-analyst.net
Sun Dec 13 18:29:10 CET 2009
As a part of our project (EcoGRID.nl) we have prepared some 60 thematic
grids that we use as auxiliary predictors for species distribution
modeling. At this stage, we would like to put the gridded maps (50/100 m
base resolution) into some efficient sharable geo-database.
We will most probably put the data into the NetCDF format
(http://www.unidata.ucar.edu/software/netcdf/) because it can handle
any-dimensional array data, and because it has been in continuous
development and widespread use for many years. NetCDF grids can be read
relatively easy into R using the RNetCDF package (e.g.
http://spatial-analyst.net/DATA/readNCDF.zip). Another alternative is to
use PostGIS WKT Raster format
(http://trac.osgeo.org/postgis/wiki/WKTRaster), but this seems to be
still rather experimental (?).
Once we put the grids into NetCDF format. We plan to install OPeNDAP
(http://www.opendap.org) server on top to make the files accessible
through the web; then Geoserver (http://www.geoserver.org) or UMN
Mapserver (http://mapserver.org) to feed a WMS from NetCDF files (raster
data). Finally, we plan to add a simple OpenLayers interface on top of
that (Geoserver has it built in) to allow direct browsing of the data
and metadata (e.g. such as this one: http://africamap.harvard.edu/)
Just to be clear, we want to put the data on a server because we would
like to run a number of operations directly on the server (via rgdal?):
1. Overlay some point data and get the values of grids (without a need
to download the grids locally);
2. Subset/mask and resample gridded data of interest (for a given
bounding box and proj4 string; again without a need to download the data
3. Upscale the grids from 100 m to 250, 500 m and 1 km resolution (then
download the upscaled grids).
4. Write/upload new grids to the database (e.g. using WebDAV).
5. Browse the grids (and metadata) via the OpenLayers.
These are only our wishes of course. We do not know if all this is
really possible with the current software.
Any examples or comments/suggestions/experiences are welcome (before we
start installing and testing the functionality).
Tomislav Hengl and Lourens Veen
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