[Mapserver-users] Tileindex questions.

[Ed McNierney]

Bob -

As the ratio of needed files to total files grows, the TILEINDEX becomes
less useful, but it is so very inexpensive - and the rendering of every
tile in the dataset so expensive - that I can't imagine it being a
liability.

As you produce lower-resolution levels of image pyramid, it DOES make
sense to merge the files into larger-sized tiles, and this will reduce
the benefit of the TILEINDEX since as the total shrinks the needed/total
ratio will grow.  Having lots of tiny files is *much* less efficient
than having a few larger files.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com
-----Original Message-----
From: Bob Basques [mailto:bob.basques@ci.stpaul.mn.us] 
Sent: Friday, March 26, 2004 5:28 PM
To: Ed McNierney
Subject: Re: [Mapserver-users] Tileindex questions.

Ed McNierney wrote:

>Bob -
>
>No, creating seamless edgematched tiles does not take care of that 
>aspect.  It doesn't address the issue of how MapServer determines
>*which* of the 528 files needs to be used to produce a requested map.
>  
>
I get that aspect of it, I was really wondering at what point the
tileindex becomes less effective at it's purpose, of increase response
performance.

bobb

>If you're requesting an image that requires most of the source images, 
>a TILEINDEX won't help much.  But you'll have other problems - if you 
>think that's going to happen (in your case you say it won't) you should

>have resampled lower-resolution images available to serve those 
>lower-resolution requests.  Otherwise you're going to be reading a 
>zillion pixels from disk only to throw away most of them.
>
>  
>



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