[OpenLayers-Dev] Layer is completely redrawn when panning passed 180th meridian.

[pdecker]

Hello,

I'm not allowed to share the server.  By world wrapping are you referring
to:
wrapDateLine: true ?
We are using the wrapDateLine parameter.

The bounding box below:
ULLon=179:59:06E
LRLon = 179:59:06W
ULLat = 00:00:45N
LRLat = 00:00:45S
is a conversion done by our wms server on the OpenLayers bounding box.  For
the 
most part, the bounding boxes sent by OpenLayers are WMS compliant.  I have
seen
some problems right around the 180th meridian...please see my other email.

Do you know why the redraw is occurring when panning?  It only happens when
the 
180th meridian overlays the vertical center of the viewing area.  This
problem occurs
in Internet Explorer.  Things get worse with Firefox where the image just
disappears.
I have looked at the requests coming from OpenLayers.  When panning, many
times 
no requests are being sent, but the image is still redrawn (or erased in the
case
of Firefox).

Thanks for any help on this matter.

-Paula


Christopher Schmidt-4 wrote:
> 
> On Wed, Dec 19, 2007 at 06:07:40AM -0800, pdecker wrote:
>> 
>> Hello,
>> 
>> Our wms server and OpenLayers 2.5 client has the following behavior.  An
>> image which spans the 180th meridian has the following upper left
>> longitude,
>> lower right longitude, upper left latitude, and lower right latitude.
>> 
>> ULLon=179:59:06E
>> LRLon = 179:59:06W
>> ULLat = 00:00:45N
>> LRLat = 00:00:45S
> 
> That's strange. Can you share the URL that this tile is requesting? Can
> you share the OpenLayers config that is resulting in this? A standard
> WMS should not be requesting an image like this, unless, perhaps, you
> are using the 'gutter' property?
> 
>> The image displays, zooms, and pans very well with one exception:  when
>> the
>> image is panned (to the east or to the west) so that the 180th meridian
>> of
>> the image is in the center of the display area, the image is completely
>> redrawn.  
> 
> This is a limitation of the current world wrapping coe, which it sounds
> like you are using. Can you confirm that you are using this?
> 
>> I have looked at the bounding boxes that OpenLayers requests from
>> the WMS server.  The server is sending back a blank tile only for the
>> bounding boxes which are outside of the image.  This problem is annoying
>> if
>> the image is zoomed in so that it completely fills the display area. 
>> Each
>> time the image is panned so that its 180th meridian section passes the
>> middle of the display area, the entire display area is redrawn.
>> 
>> Are there any suggestions to remedy this problem?
> 
> The world wrapping code is a hack. Doing something more intelligent with
> it is very difficult, since OpenLayers is designed not to be used in
> this manner. Specifically, you would have to teach OpenLayers that the
> tiles from -180 -> -170 is the same as from 180 -> 190, which we have
> not done. It might be possible -- probably in a custom layer class --
> but there is no strong motivator towards it.
> 
> Regards,
> -- 
> Christopher Schmidt
> MetaCarta
> _______________________________________________
> Dev mailing list
> Dev at openlayers.org
> http://openlayers.org/mailman/listinfo/dev
> 
> 

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