[mapserver-users] Using nquery/mapxy/TOLERANCE/TOLERANCEUNITS

[Brent Fraser]

Steve,

   So the alternative to using imgxy is to send mapserver:
      mapxy and mapext and imgext (where mapext=imgext) and imgsize?
Hmm, I think I tried that, but I'll take a closer look.

Sounds like the better solution is just to change Geomoose to use imgxy.

Thanks!
Brent Fraser

Steve Lime wrote:
> It's possible to use mapxy in conjunction with TOLERANCEUNITS PIXELS but you
> have to understand how pixel size is computed for it to work as expected. The 
> assumption is that there's a map associated with the point query and it's defined
> by a map extent, a width and a height. 

I thought that was imgext and imgsize?


> So, you'd need to define those somehow
> too. If not explicitly set as part of a query the defaults in the mapfile are used which
> is where things could get convoluted. I can't recall what happens if you define 
> mapxy AND mapext with mode=nquery though, which takes precedence in setting
> the query method? (looks ambiguous in the code)

Could be a implementation/support headache...


> Practically speaking, if a query or whatever is associated with a map image regardless
> of client environment I *always* use imgxy, imgext and imgsize and populate those
> from the client and let MapServer do the conversion. Works fine with the environments 
> I use frequently (e.g. OL and dBox). This site does it extensively via OL:

I'm off to hack GeoMoose!

> 
>   http://www.dnr.state.mn.us/waters/csg/index_beta.html
> 
> Steve
> 
>>>> Brent Fraser <bfraser at geoanalytic.com> 10/01/09 10:51 AM >>>
>    I'd like someone to confirm my understanding of using 
> nquery/mapxy/TOLERANCE/TOLERANCEUNITS.
> 
>    GeoMoose v1.6 sets mapxy and imgext (along with mode=nquery and imgsize) CGI 
> variables when doing an "Identify Feature" operation.  I'd like to use 
> TOLERANCEUNITS PIXELS (and TOLERANCE 3) for my point layer because I think it's 
> more intuitive over a range of scales (as opposed to TOLERANCEUNITS METERS, 
> TOLERANCE 500).
> 
>    This is not possible as using Mapserver's mapxy requires the map file to have 
> TOLERANCEUNITS METERS to work properly.  If I want to use TOLERANCEUNITS PIXELS, 
> I must use imgxy instead of mapxy because mapserver does not do the conversion 
> from mapxy mapping coords to imgxy image coords.
> 
> Is this correct?
> 
> Thanks!
> Brent Fraser
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