[Mapserver-users] Tileindex questions.

[Ed McNierney]

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


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