[Mapserver-users] Tileindex questions.

[Howard Mark]

Ed,

A very good point. Let me interject one idea that I've used that really speeds up performance. 
I use a tile index and check performance by zooming in to about 1:20K. Then I zoom out until performance drops. 
I create a new tile grid shapefile using that map extent as the size of one tile. I tile the entire map area (in my case the world). 
I create a new aggregate image layer using calls to the map server to generate an image for each new tile.
I repeat this process until I have good performance at any scale. I then tune the scales in the map file to match the layers.
This "pyramid" scheme is used in several map server products.
Granted 528 images are not that many - but displaying all at once takes a bit of time.
I've created a world mosaic from 360,000 images that displays at any scale in no more than 4 seconds.

Mark




-----Original Message-----
From: mapserver-users-admin at lists.gis.umn.edu [mailto:mapserver-users-admin at lists.gis.umn.edu]On Behalf Of Ed McNierney
Sent: Friday, March 26, 2004 2:28 PM
To: Bob Basques; Mapserver List
Subject: RE: [Mapserver-users] Tileindex questions.

Bob -

I'm not quite sure what you mean by "composite layer" as opposed to
TILEINDEX, but you should certainly use a TILEINDEX.

A TILEINDEX is a very efficient way for MapServer to determine which
source images overlap the requested output area.  In your example, any
given map request *ignores* 97% of the files.  Instead of making
MapServer open every file to see whether it's interesting, the TILEINDEX
will very quickly determine WHICH 16 files you need for a given request,
without even touching the other 512.

It is in just such cases that a TILEINDEX is very helpful.  If you were
going to end up using all 528 images in the output anyway, there
wouldn't be much point in quickly figuring out which ones you needed.
When a small number of tiles from a large dataset are to be retrieved, a
TILEINDEX is the way to go.

        - Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com
-----Original Message-----
From: Bob Basques [mailto:bob.basques at ci.stpaul.mn.us]
Sent: Friday, March 26, 2004 3:38 PM
To: Mapserver List
Subject: [Mapserver-users] Tileindex questions.

All,

Some guidance please.

I have 550 megs consisting of 528 tiles of data.

The question, should this be a composite layer, all in one, or should I
be using a TILEINDEX instead.

At what point is the TileIndex overkill?  We will not be loading much
more than 16 tiles at a time for any one request.

bobb


_______________________________________________
Mapserver-users mailing list
Mapserver-users at lists.gis.umn.edu
http://lists.gis.umn.edu/mailman/listinfo/mapserver-users


_______________________________________________
Mapserver-users mailing list
Mapserver-users at lists.gis.umn.edu
http://lists.gis.umn.edu/mailman/listinfo/mapserver-users


********************************************************************************
This message is intended only for the use of the Addressee and may
contain information that is PRIVILEGED and CONFIDENTIAL.

If you are not the intended recipient, you are hereby notified that any
dissemination of this communication is strictly prohibited. If you have
received this communication in error, please erase all copies of the
message and its attachments and notify Space Imaging immediately.
********************************************************************************