[Geomoose-users] Geomoose2 and MapServer tolerance

[Dan Little]

Hi Johan,

Is there any chance you can attach your mapfile for the effected layer?

Also, if UTM-15 is not the coordinate system you want to use you might want to check out:
http://www.geomoose.org/moose/docs/projections.html

It may make maintenance of your application easier over the long term.


----- Original Message ----
> From: Johan Forsman <Johan.Forsman at LA.GOV>
> To: "geomoose-users at lists.sourceforge.net" <geomoose-users at lists.sourceforge.net>
> Sent: Monday, September 14, 2009 2:55:01 PM
> Subject: [Geomoose-users] Geomoose2 and MapServer tolerance
> 
> Hello All:
> 
> Before I pester anyone with one of my many questions I wish to say "Thank You!" 
> to the authors of Geomoose, OpenLayers, and MapServer. Discovering these 
> products just recently I have been able to, in relatively short order and in 
> spite of exceptionally weak programming skills, assemble a usable web mapping 
> application for internal use in our state drinking-water program. This is really 
> quite fantastic. I simply took the demo app included with Geomoose2 and adapted 
> it (more or less successfully) to our needs. So far I have only needed to invest 
> time and aspirin, a bargain by any measure.
> 
> Now, on to question one of several thousands:
> 
> Not counting the base map data, our data are mostly for water-well locations in 
> point form. I have projected all data to NAD83 UTM15N using my desktop GIS 
> application prior to uploading it for use with Mapserver.
> 
> The identify tool works quite nicely, but I am having some issues with the 
> tolerance. Specifically, it appears the tolerance is not recalculated when the 
> scale changes. If I use ground units (meters) in my map file I would expect this 
> to be the case, but if I use pixels I would expect the linear distance 
> represented by one pixel to change depending on the scale.
> 
> 
> The map is 800x650, and maximum extent is at just under 1:3 million.
> If I use pixel units and a tolerance of 1, my back-of-envelope calculation 
> estimates each pixel at ~850 meters or so. If I zoom in to 1:24000 and use the 
> identify tool, it will still return every well in an ~850 meter radius. This 
> becomes problematic.
> 
> Using units of meters I can clearly be much more selective, but then on the 
> other end of the scale I can't hit anything "just right" to obtain any results.
> 
> If anyone can enlighten me I would be most grateful, and if I am missing 
> something completely obvious and by this am wasting everyone's time, I apologize 
> in advance.
> 
> Respectfully,
> Johan.
> 
> ----------------------
> Johan Forsman, M.Sc.
> Geologist
> Safe Drinking Water Program
> Louisiana Department of Health and Hospitals
> Office of Public Health
> Telephone: 225.342.7309
> Telefax: 225.342.7303
> 
> 
> 
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