[mapserver-users] disappearing point features in North America

[Chris Green]

I have a problem that may be down to OpenLayers or to Mapserver, or (just as
likely) to me. Basically I am using OL to request WMS maps from Mapserver,
and the map consists of point features with a global spread, typically
around 100 points in each map. The points are defined in a table which has
lat/lon in decimal degrees, and these are converted to 900913 by Mapserver
where my mapfile has an overall projection of epsg: 900913 but the points
layer has projection epsg: 4326.

 

The map is defined in OL with extents: -20037508.34, -20037508.34,
20037508.34, 20037508.34 and the mapfile has the same extents applied.

This all works fine when a map is first displayed, all of the points are
present on the map. However when I scroll the map left or right there is a
'dead spot' where  all the points in North America disappear and then
re-appear, either side of the dead spot. Looking with Firebug at the
bounding box that OL uses to request the map from Mapserver I can see that
the points disappear when the bounding box is between left bounds of about
-23700000 and -33700000. Only the points in North America are affected,
never those in Europe or Asia. 

 

I have been wrestling with this for quite a while, experimenting with
extents etc, all without any effect.  Does anyone recognise where my problem
may lie, or else have any suggestions how to diagnose what is going on?

 

 

Chris  

 

 

 

 

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