On Sep 27, 2011, at 2:03 PM, Paul Ramsey wrote: > Once you have vectors, the classic trick I've seen for doing the barbs > is to do math to map the windspeed into an appropriate char() value > and store the barbs as TTF font entries. So you only end up with one > class, and the barb is an appropriately rotated label.
This might help http://carocoops.org/bb/viewtopic.php?t=169 > > P. > > On Tue, Sep 27, 2011 at 10:31 AM, Brent Fraser <[email protected]> > wrote: >> At FOSS4G I was struck by the number of presentations involving weather >> data and time series display. Maybe I noticed because I have a need to >> render wind velocity in KML, and while I haven't settled on mapserver to do >> the rendering I've been wondering how to render wind barb symbols (see >> attached graphics) efficiently. >> >> One problem is the source data: the magnitude is in one raster file (GRIB >> format, float64) and the direction in another. GDAL's OGR library will >> read the GRIB files, but I don't know of any way to use two rasters to >> define a vector layer. I think there is some work going on with respect to >> displaying vector field data in mapserver, so maybe this will be solved by >> that work. Otherwise pre-processing the two rasters into a point datasource >> containing lon,lat,speed,direction attributes may be the way to go. >> >> The other issue of wind barb symbol rendering may have to be solved by hand >> constructing a barb for 0 knots, 5 knots, etc (50-ish symbols?) , and having >> 50-ish corresponding classes (this could be a performance problem for >> mapserver). But I'm open to better ideas... SLD? HTTP/CGI request?, >> something like one class of: >> >> CLASS >> STYLE >> GEOMTRANSFORM "start" >> COLOR 0 255 0 >> SIZE 15.0 >> SYMBOL "http://localhost/symbolgen?[speed]"; >> ANGLE [direction] >> END >> END >> >> but likely the cost of getting the symbol would be greater that creating 50 >> separate class objects. >> >> And for those interested in mapping and graphing weather data, have a look >> at http://www.ncl.ucar.edu/Applications/ >> especially http://www.ncl.ucar.edu/Applications/barb.shtml >> >> -- >> Best Regards, >> Brent Fraser >> >> >> _______________________________________________ >> mapserver-users mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/mapserver-users >> >> > _______________________________________________ > mapserver-users mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/mapserver-users
_______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
