[mapguide-users] MrSID files through GDAL FDO provider

[Andy Morsell]

Hi Jonathon,
All of my answers refer to 1.2 RC1.
 
Yes, the GDAL provider does try to hit all of the images in the feature
source when the map is first accessed regardless of whether that layer is
actually visible.  This issue has been entered by me into Trac already.  
 
I have seen the ECW and MrSID providers trying to access the same image
files as well.  Doesn't make sense to me either.
 
I am currently running a client site with 10 GB of ECW imagery, each about
25 MB and seeing relatively good performance (except for the first issue
above).  So, perhaps your issue is more confined to the MrSID format?  In my
case, the data started as JPEG2000 format which the GDAL provider could not
successfully read so I used fwtools gdal_translate to convert all of them to
ECW.  Perhaps translating your MrSID's to ECW's would help in this case?
Also, Jason Birch and others are working on image tile index support for
directories of images which could help with your particular problem.
 
By the way, here are some of the GDAL issues I have logged with the 1.2 beta
that might be of interest:
 
http://trac.osgeo.org/mapguide/ticket/191
http://trac.osgeo.org/mapguide/ticket/187
http://trac.osgeo.org/mapguide/ticket/160
 
 

Andy Morsell, P.E. 
Spatial Integrators, Inc. 
http://www.SpatialGIS.com 

  _____  

From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Jonathon
McIntyre
Sent: Wednesday, June 13, 2007 12:21 PM
To: mapguide-users at lists.osgeo.org
Subject: [mapguide-users] MrSID files through GDAL FDO provider



Good morning,

I am working with MGOS 1.2 RC1 and the latest GDAL FDO providers on XP Pro.

 

I have a directory with twenty five 40MB MrSID files in it.  If I create a
single data source against that directory, I have a limited possibility that
the images will actually process although there does not seem to be any
errors when I run MGServer from the command line. It appears that the
datasource is processed whether or not the layer is turned on.

 

As an aside,  I did notice that if I have the ECW dll in the directory, the
messages indicate that it is trying to read the .sid format files as ECW
which adds to the time.

 

In order to test things out, I created a data source for each file.  I
noticed that for a couple of files, the processor usage spikes to 100% but
the images are displayed quickly.  As I add more files, the processor spikes
become longer and the delays far more apparent.  When I get all 25 added my
processor spikes to 100% usage for several minutes although the images will
eventually display.  Watching the mgserver from the command line shows that
the images process and some go very quickly but others seem to be very slow
(which may just be the result of the processor being pegged).

 

I tried using fwtools to mosaic these images together but can only get about
4 together before I hit the 4GB tiff limit.

 

I am trying to create a new single mosaiced .sid file to see if that will
make a difference but was wondering if there were any other ideas of what I
could do to improve the performance of the display of the images?

 

Thanks,

J

 

 

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