[R-sig-Geo] Making web-repository of gridded maps: NetCDF or WKT Raster?
hengl at spatial-analyst.net
Mon Feb 8 09:54:15 CET 2010
> -----Original Message-----
> From: Pierre Racine [mailto:Pierre.Racine at sbf.ulaval.ca]
> Sent: Friday, February 05, 2010 4:49 PM
> To: Tomislav Hengl; r-sig-geo
> Subject: RE: [R-sig-Geo] Making web-repository of gridded maps: NetCDF or WKT
> Hi Tom,
> I understand that PostGIS WKT Raster is still under development but it is
> designed to answer exactly the kind of problem you are confronted with: serving
> as a warehouse for huge raster datasets, integrate them with vector (PostGIS)
> through raster/vector GIS operations (raster/vector overlay, raster operations
> like resampling, mask, mapalgebra), all this using a common SQL interface. WKT
> Raster intent to be a final elegant solution to this kind of problem avoiding the
> development of multi layer applications like the one you are envisioning. WKT
> Raster intend to make of PostGIS a complete SQL GIS solution handling both vector
> and raster data.
> As a matter of example we started the WKT Raster project to be able to intersect
> thousands of vector buffers with many raster dataset covering the extent of
> Canada (many in the 30 GIG order). Our final goal is to enable our users to do
> that on the web (even if some query may take days).
> Note however that WKT Raster is not a web server. MapServer, Geoserver and
> OpenLayer will have to be adapted to support WKT Raster. There is already a GDAL
> driver able to read WKT Raster from the database.
> This said, I invite you to consider a contribution to the WKT Raster project (or
> one to the other web project like MapServer, GeoServer or OpenLayer: adding WKT
> Raster support to them) in order to concentrate your efforts on a generic
> solution to problems similar to your one, contributing to the whole community,
> instead of disseminating your energy on a specific solution, serving only your
I am sorry that you might got me wrong (and thank you for your reply even with some months of delay!). I do intend to test also WKT Raster and will certainly report on my results via R-sig-geo. We are just in a process of setting up our server and installing all functionality. Provided that we find your software suitable, efficient and secure (in comparison to e.g. rasdaman or NetCDF), I would be willing to contribute more actively e.g. to your wiki [http://trac.osgeo.org/postgis/wiki/WKTRaster] (certainly by reporting on the results using same sample data-sets).
I am not sure about what kind of set-up do you have with your employer, but my project (EcoGRID, client: Dutch Ministry of Agriculture, Nature and Food Quality) needs to stay a priority of course. The art is to be able to satisfy your employer and still contribute to open access projects such as yours.
> Pierre Racine
> WKT Raster Project Manager
> >-----Original Message-----
> >From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-
> bounces at stat.math.ethz.ch] On Behalf Of
> >Tomislav Hengl
> >Sent: 13 décembre 2009 12:29
> >To: r-sig-geo
> >Subject: [R-sig-Geo] Making web-repository of gridded maps: NetCDF or WKT
> >Dear R-sig-geo,
> >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
> >R-sig-Geo mailing list
> >R-sig-Geo at stat.math.ethz.ch
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