[Mapserver-users] Mapserver Newbie Quests

Frank Warmerdam warmerdam at pobox.com
Fri May 14 10:03:50 EDT 2004

Zornig Jürgen wrote:
> Hello, all
> I have set up Mapserver Win Binaries (4.2 beta2) on a Windows 2000 Server Machine, because of the ECW Support of GDAL. The Server only should Serve a bunch of ECW Color Images per OGC Service at a good performance. So I created a tile index over the Fotos (~10000 Mosaics in endconfig) as shapefile. This works fine but there are also a lot of problems, I can not solve with my mapserver skills.
> Problem 1: Can I use a tile index, served by a PostGIS Database? Is that faster (more perormance)?


I don't think so though it might work in 4.3.  In any event, I don't think
it would give better performance than a spatialling indexed shapefile.

> Problem 2: When I zoom out too much, mapserver needs exponentially more time to process the input ecw´s to a output jpeg. How can I tune that best? (Pyramids? How?)

The GDAL ECW drivers are not necessarily all that efficient at processing requests
from alot of ECWs.  There should be no need to generate pyramids for the individual
ECW files, but having a pre-cooked overview layer to switch to at a particular scale
might be a wise idea.

> Problem 3: On the Server, there are running lots of instances of mapserv.exe, which I can´t kill, because "Acces denied!" (I´m root on that machine). COuld there be some misconfiguration?

Got me.  However, I would like to stress that the MapServer beta-2 is seriously
broken for raster data (as I announced to the list a few days ago), and should not
be trusted for raster use.  It is likely to suffer heap corruption and seg faults
at any time when raster layers are used.  I am hoping Paul will replace the package
with a Beta 3 version very soon which has the raster bug fixed.

BTW, the raster bug was my fault and resulted from a sloppy fix to the "raster
cracking" problem.   In fact, it took 3 fixes before I got it right (I hope).

> Problem 4: I´m testing this configuration (mapserver + ecw Imagery + tile index), to find a method to serve very large raster data for our ArcIMS Services, ArcGIS Applications and AutoCAD Clients. Do you think, there might be a better solution? For my part, mapserver could do this good (if I could admin it perfectly), but maybe there is a much better solution.

Honestly, I am not confident of performance with ECW files.  If you have the
disk space I would be more comfortable doing this with GeoTIFF files for
each tile with lots of overviews built, and a pre-prepared overview file
for use at broad zoom level.  Any view that involves opening alot of individual
files may suffer unexpected performance issues.

If you really want to use ECW files be prepared to fiddle about a bit, and/or
to fund additional engineering work to fine tune performance.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

More information about the mapserver-users mailing list