WMS Raster Layer service

[Brent Fraser]

Ganesh,

  In general the answer is to use a TILEINDEX layer.  Use a TILEINDEX layer
if you have a set of rasters each covering a separate area but form a single
logical layer (USGS 1:250k topos for example).  With a TILEINDEX Mapserver
will automatically select the rasters covering the current map extent as the
user pans and zooms.

  If your rasters cover the same area but represent different times (e.g.
satellite images of Minot from 2000 to 2004), things are more complicated
when it comes to WMS.  In your original email you mentioned "the most recent
image" so I wasn't sure how important time was in your implementation...

Brent Fraser
bfraser at geoanalytic.com

----- Original Message -----
From: Ganesh P
To: MAPSERVER-USERS at LISTS.UMN.EDU
Sent: Monday, January 10, 2005 12:54 PM
Subject: [UMN_MAPSERVER-USERS] WMS Raster Layer service


Hello everyone,

We have been successfully using Mapserver(PHP/Mapscript) for WMS client and
Server and everything is working fine. Thanks to all the MapServer
Developers and Users. Currently, we are using WMS server to deliver vector
layers as PNG images. Now, we are planning to extend the server
functionality by delivering Raster layers(GeoTiff) as PNG images.
Currently, in our system we have around 600 geotiff images. In our
standalone system, We search the database everytime with the current map
extent and display a list of images covering the current extent. When the
user selects an image, that image will be displayed on the map window. This
is how we implemented our system. The map file contains a raster layer with
DATA field set dynamically (using PHP/Mapscript) with the image name. We
would like to do the same for WMS server, that is, when the client requests
a raster layer using a bounding box in the URL, the most recent image which
covers the requested bounding box should be searched in the database and
returned to the client as PNG.

My concerns are:

1. How do we set the raster layer in map file for WMS server and dynamically
fill in the DATA field with the exact image name (out of 600 images)
covering the bounding box?

2. Can we use Mapserver to do this, or do we have to write a custom program
to read the WMS client's URL, manually search the database, Cut the image
for the requested bounding box, convert the image into PNG and send it to
the client ?

Any suggestions or information is greatly appreciated.
Thank You very much in advance.

Regards

Ganesh Pulicherla
Digital-NGP Developer
Upper Midwest Aerospace Consortium
University of North Dakota