[Geomoose-users] Geomoose2 and MapServer tolerance

Wed Sep 16 09:25:48 EDT 2009

Hello Dan, thank you for the prompt reply.

I have attached one of the affected map files. To emphasise, ALL my map files exhibit this behavior.

I checked again just now to confirm and with a pixel tolerance of 1, at 1:24000 scale, clicking the identify tool on a well returns all the wells in that specific well yard (about 20 meter radius), plus another facility 629 meters away (the nearest facility outside the well yard).

At that scale my map window is 800x650 pixels and approximately 7400x5656 meters as measured by the tool in the application. These measurements ought to translate to 9.25 m/px in the x direction and 8.70 m/px in the y direction.

I have confirmed that the units convert correctly in the drop-down box, just in case.

Regarding coordinate systems, our data is maintained in NAD83 by state standards decree, and I use the UTM projection for easier measurements and more visually pleasing geometries. It seemed a reasonable choice at the time.

Thanks!
/Johan.

-----Original Message-----
From: Dan Little [mailto:danlittle at yahoo.com]
Sent: Monday, September 14, 2009 3:01 PM
To: Johan Forsman; geomoose-users at lists.sourceforge.net
Subject: Re: [Geomoose-users] Geomoose2 and MapServer tolerance

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
>
>
>
> ------------------------------------------------------------------------------
> Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day
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> https://lists.sourceforge.net/lists/listinfo/geomoose-users

-------------- next part --------------
MAP
	NAME 'wells'
	SIZE 800 650
	STATUS ON
	EXTENT  401488 3197075 909651 3653904
        UNITS METERS
	INCLUDE "../../geomoose_globals.map"
	WEB
		INCLUDE "../../temp_directory.map"
	END
	LEGEND
		STATUS ON
		LABEL
			TYPE TRUETYPE
			FONT arial
			SIZE 8
			COLOR 0 0 0
		END		
	END #legend
	QUERYMAP
		STATUS ON
		STYLE SELECTED
		COLOR 0 255 0
	END

LAYER # Wells in the SDWIS database
	NAME 'sdwis'
	DATA './SDWIS_wells'
	TYPE POINT
	STATUS on
	LABELITEM "FacilityID"
    LABELCACHE ON
    LABELMAXSCALE 25000
	FILTERITEM "SystemActi"
	FILTER "A"
	CLASSITEM "FacilityAc"
	CLASS
		NAME "Active"
		EXPRESSION "A"
		STYLE
			SYMBOL 'circle'
			SIZE 8
			COLOR 0 0 254
		END #style
		label
			type truetype
			font arial
			size 8
			color 0 0 0
			position auto
		end #label

	END #Active class
	CLASS
		NAME "Inactive"
		EXPRESSION "I"
		STYLE
			SYMBOL 'circle'
			SIZE 6
			COLOR 254 0 0
		END #style
		label
			type truetype
			font arial
			size 8
			color 0 0 0
			position auto
		end #label
	END #Inactive class
	METADATA
		'identify_record'	'identify_well.html'
		'select_record'	'select_well.html'
		'select_header' 'select_header_wells.html'
		'popups' 'wells_popup.html'
		'itemquery'	'wells_itemquery.html'
		'itemquery-filteritem' 'PWSID'
		'itemquery-filter'	'/.*[qstring].*/i' 
		'qstring_validation_pattern' '.'
		# Feature reports are stored in the conf/feature_report directory.
		'feature_report' 'well.xml'
	END #metadata
	TOLERANCEUNITS pixels
	TOLERANCE 1

END #Layer sdwis

END ## end Map