A really weird problem with querying a map
David.Fawcett at STATE.MN.US
Wed Oct 31 16:44:05 EDT 2007
I am not offering this up as complete solution to your problem, although
it would be cool if it was a viable work around.
I think that this behavior is new in 5.0, but I could be wrong. I was
thinking that if adding a tolerance to your query changed the result, it
would help us tease out enough symptoms to get a viable bug report.
It would be interesting to run a test to see if this occurs on a layer
where the layer and output are the same SRS. (e.g. pre-project your
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Gregor Mosheh
Sent: Wednesday, October 31, 2007 2:37 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] A really weird problem with querying
Fawcett, David wrote:
> I ran into something with 5.0 and didn't think that much of it. If
> you haven't defined a TOLERANCE and TOLERANCEUNITS. Try a tolerance
> of 1 meter or something like that.
Well, this is something...
Of note: The data layers are in geographic with NAD27 (EPSG:4269),
whereas the map's output projection is UTM zone 9 NAD 27 (EPSG:26709).
Evidently this is very relevant when it comes to queries.
I set these:
and it works well enough to do the job.
But not well enough for me to understand what's happening.
I do find this odd. The documentation says that the defaults for polygon
layers are "0 pixels" meaning that one must click inside the polygon.
This would be just perfect, but instead I get "nothing found" if I leave
it at that default.
I find it odd that I should have to use such a huge tolerance, too. If I
reduce the tolerance, I start getting all sorts of false positives:
clicking too close to a border will bring up the neighbor's info. I find
that confusing: I'd think that to be a side effect of a *higher*
tolerance being set, yes?
Gregor Mosheh / Greg Allensworth
System Administrator, HostGIS cartographic development & hosting
"Remember that no one cares if you can back up,
only if you can restore." - AMANDA
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