Strange behavior ....

[Stephen Lime]

I'm not a projection expert. One could certainly test PROJ behavior at
extremes outside the mapserver using the utlities included in the PROJ
distribution. Could also be some data precision/rounding issues at 
extremes. All cordinates in MapServer are doubles. Could also be
limitations in the base projection, or at least how it's implemented in
proj? The base data appears to draw ok though, correct?

Steve

Stephen Lime
Internet Applications Analyst

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Daniel Morissette <danmo at videotron.ca> 09/13/00 01:49PM >>>
JF,

We have an application that does something similar to yours: we display
a layer of points in LAT/LON on top of a base map in LCC and we noticed
the same thing as you.  We haven't investigated the problem yet,
though...

Steve, are you aware of any PROJ.4 limitations that could explain that
behavior?  It seems to be that LAT/LON points located north of a
specific latitude are lost.  And the latitude at which points starts to
disappear changes depending on the scale of the map: as you zoom in, the
line where points start to disappear moves north.

Any idea?

Daniel

"Doyon, Jean-Francois" wrote:
> 
> Hello !
> 
> Well, things are oging pretty well, but now I've run accross a strange
> behavior
> I was hoping someone could explain ...
> 
> When I map my search results (using php-mapscript as allways), I create
> atemporary shapefile.
> This shapefile use geographical coordinates, whereas the rest of the data
> used to generate the
> map uses a different projection (lcc to be exact).
> 
> Now for some reason, results don't seem to show up in the far north
> (Nunavut) !
> Actually, they do show up, but only once I zoom in ! Now, I am *NOT* doing
> anything to that layer
> that might do this, the layer is "ON" by default, and that's it. All the
> Other symbols show up.
> Actually results in Iqualuit show, but not other smaller Nunavut communities
> ... Until I zoom in.
> 
> I'm wondering why this might be, and how to fix it ... I'm guessing the
> projection conversion might
> have something to do with it ? But that's out of my area of expertise ...
> 
> Any ideas ?
> 
> Thanks,
> 
> Jean-Francois Doyon
> Internet Service Development and Systems Support
> GeoAccess Division
> Natural Resources Canada
> (613) 992-4902

-- 
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 Daniel Morissette                       danmo at videotron.ca 
              http://pages.infinit.net/danmo/ 
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