Making web-repository of gridded maps: NetCDF or WKT Raster?

-----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
Raster?

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
organisation.

Thanks,

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 d?cembre 2009 12:29
To: r-sig-geo
Subject: [R-sig-Geo] Making web-repository of gridded maps: NetCDF or WKT

Raster?

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
locally);
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).

Thanx!

Tomislav Hengl and Lourens Veen