[Mapserver-dev] Advanced support of grid format (visualization, interrogation, analysis)

[Steve Lime]

There is definite movement away from native support for any grid format
in MapServer
in favor of the GDAL library. I've kind of wanted to go GDAL
exclusively but Frank see's
value in a really vanilla configuration of MapServer without the need
for GDAL but with
TIFF support. Problem is that the native TIFF support is so far behind
GDAL TIFF support
that it can be quite confusing to users.

Anyway, assuming GDAL is the future then it would make sense to
integrate analytical
capabilities at that level. MapServer already supports simple raster
processing directives
to control GDAL so much of the work has been done. I wonder if GDAL
itself really aspires
to provide that level of functionality or if would be best to leverage
something existing
like GRASS.

Raster queries are another matter and have been talked about over the
past couple of
years. A basic scheme exists, it's not been high enough priority to
persue at this time.
This work WOULD be MapServer specific although again it would leverage
GDAL heavily
for the data.

For what it's worth, the UMN has done some of this work already, but
because most of
it was research oriented it has not made its way into the source tree.
This work did not
leverage GDAL though.

Bottom line is that the type of functionality you'd like to see added
is a good idea and I 
would be interested in working on it, as might others (I hope).

Steve

>>> Claude Philipona <claude-mapserver at skirando.ch> 10/2/2003 3:30:48
PM >>>
Hello,

What is exactly the state of grid format handling in Mapserver? Present
and
near feature. We have some people asking for some "advanced" features,
with
fundings available. I don't know if somme of the needs are alreday
available or planned...

Here is a first rough description of their needs:

For GIS application, there are several models for representing the
real
world (object based, field based) : simple vector, topological vector,
TIN, raster,...  Each of these models have advantages and drawbacks
and
are more suited for particular problems (topological vector for
utilities management, raster for DTM analysis, etc.).  Raster format
is
often used for background data (orthos, satellite,...) but can also be
used for all kind of continous data (visualisation, interrogation,
analysis for : DTMs, slope, orientation, convexity, radiation data,
pollution, income,...) and discrete data (soil occupation,...)

All web mapping solutions include the support of simple vector
(visualisation, interrogation) and raster (visualisation) ? but few
(or
none) include the complete support for raster data (interrogation,
analysis).  In desktop or professional GIS, these functions are
included or
in extensions (Spatial Analyst for Arcview, Vertical Mapper for
MapInfo,
etc.). The objective would be to extend Mapserver to support simple
analysis function for raster (or grid) data (interrogation first,
analysis). Mapserver uses GDAL lib that supports some grid formats
(Arc/Info Binary Grid (.adf), Arc/Info ASCII Grid, Military Elevation
Data
(.dt0, .dt1), GRASS Rasters, USGS ASCII DEM (.dem), ?).
The objective of the developpement would be to add to Mapserver
the possibility to support visualisation, interrogation (and
eventually
simple analysis) for continuous data. The objective would not be to
develop complex analysis functions available in desktop or
professionnal
GIS (at first) but to add some basic functions to present the results
of
these analysis. 
Mapserver could return the pixel value for gridded data (elevation,
slope,
pollution concentration, average income,..). Simple function allowing
to
get information for a gridded format (height in the example below). We
could use this function to build a more sophisticated function like a
cross
section.

This  developpement could be funded by several Mapserver users. It
could
give Mapserver an interesting competitive advantage.

These developpements should be done conforming to OGC and ISO
standards
: there are many initiatives addressing portions of the overall scope
of
this Topic Volume. Important among them is the ISO TC/211 initiative
to
add a work item to address raster and image data types. OGC and ISO
TC/211 intend to work closely to achieve common specifications.


Would you have interest in adding such features in Mapserver?

Claude
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