[Mapserver-users] .tiff resolution

[Ed McNierney]

Charlton -

You're suffering from what my friend Bob Frankston calls "premature optimization".

Unless you're planning on a high-volume commercial setup, stop worrying about performance.  And even if you are planning high volume, get it working well first as a prototype, THEN worry about performance.

Just toss all the shapefiles on to your map and see what happens.  There are a variety of performance tweaks you can make to optimize your vector data.

The problem with a pre-generated raster is that it will really only look its best at the exact same viewing scale used to render it.  Raster images that are really rendered line art (like this is) don't rescale well.  Raster images that are continuous-tone, like photographs, can rescale a bit better.

Drawing all those vector graphics isn't that CPU-intensive at all, really, and CPUs are pretty darn fast these days (even the slow ones <g>).

	- Ed

-----Original Message-----
From: Charlton Purvis [mailto:cpurvis at asgnet.psc.sc.edu]
Sent: Friday, February 07, 2003 3:03 PM
To: Ed McNierney; Hankley, Chip; MapServer List (E-mail)
Subject: RE: [Mapserver-users] .tiff resolution


Thanks, Ed.  Yes, that's what I considered from the get-go.  But maybe it's my naiveté showing when I say that I decided to go the TIFF route since I thought that it would be more CPU intensive for MapServer to crunch the shapefile and produce nice layers than it would be for it to render the TIFF.  I can certainly accept that fact that I could be mistaken, but considering what my goals are, maybe I'm not too far off base.

Goal (at least a current one):  I would like to produce maps w/ elevation as a "layer" and then put other layers on top of it (roads, flooding paths, etc.).  Current thinking is that I don't want the server to spend time trying to render the elevation map when it should be busier working w/ the other layers.

Flip-side:  Maybe it all boils down to keeping everything consistent.  It's fair to say that if I want high resolution for the streets, then I'd better have the same resolution w/ the elevations.  And an easy way to do that would be to work w/ only shapefiles.  In theory.

But is it unreasonable (or simply dumb) to think that I can have a pretty background that is reasonably non CPU intensive to render while superimposing layers that would require higher CPU priority?  Perhaps it's time for GIS 101.  I've been a computer scientist for a long time, and I'm slowly migrating to the GIS frame-of-mind.  Slowly but surely.

Thanks, all.

Charlton

-----Original Message-----
From: Ed McNierney [mailto:ed at topozone.com] 
Sent: Friday, February 07, 2003 2:51 PM
To: Charlton Purvis; Hankley, Chip; MapServer List (E-mail)
Subject: RE: [Mapserver-users] .tiff resolution

Charlton -

If you have the data in a shapefile, you will get MUCH better output results by serving that data as a shapefile in MapServer than by converting it to a TIF and then serving the TIF.  Both processes essentially do the same thing (generate a raster image) but MapServer can customize that image each time to the requested output resolution, whereas the TIF image is frozen at a particular resolution.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242