[OpenLayers-Users] Problem Setting maxExtent for Polar Projection (EPSG:3995)

[ScottCh]

For the sake of OpenLayers users who follow this route, I'd like to point out
that the reason that the  OpenLayers Graticule Example
<http://dev.openlayers.org/releases/OpenLayers-2.13.1/examples/graticule.html>  
is able to show a polar projection with radial graticule lines is due to the
following three lines, at the top of the example's HTML page:

/[script
src="http://svn.osgeo.org/metacrs/proj4js/trunk/lib/proj4js-compressed.js"][/script]
        [script type="text/javascript"]
            Proj4js.defs["EPSG:42304"]="+title=Atlas of Canada, LCC
+proj=lcc +lat_1=49 +lat_2=77 +lat_0=49 +lon_0=-95 +x_0=0 +y_0=0
+ellps=GRS80 +datum=NAD83 +units=m +no_defs";/
            
*Note:* I changed the angle brackets to square brackets, I did not want to
inadvertently embed a script in my message.

I changed the last line above to use the EPSG:3995 projection information,
since that is the projection we are using.  This finally allowed the
OpenLayers graticule to show radial lines.  Up to that point, they were
always forming a rectangular grid.  

/However/, just as Arnd Wippermann said, the graticule works very poorly in
this mode.  Scaling and panning causes the graticule lines to do crazy
things.  I just wanted to find out why it worked differently in this
example.  It does not nearly work well enough for our software project to be
practical.

One thing is very strange about having add this projection information for
Proj.4.  We have Proj.4 installed on our server.  It installs a library file
called */usr/share/proj/epsg*, which contains the same definition for
EPSG:3995 that I added to the Proj4js.defs.  

So why does Proj.4 need to be explicitly given the projection information
that OpenLayers already has, in order for the Graticule to work?  This seems
unnecessary and redundant.

Thanks again to Arnd for your generous help!

Scott C.



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