BBOX that crosses dateline

[warmerdam]

> My question is how is a BBOX supposed to be specified in geographic
> coordinates for a region that crosses the dateline? 
> 
> If I want the 2x2 degree region with a top left corner of 179E,1N and
> a lower left corner of 179W and 1S would it be:
> 
>   BBOX=179,1,181,-1
> or 
>   BBOX=179,1,-179,-1
> or 
>   BBOX=-179,1,179,1
> 
> The second actually works with the newish WMS implementation 
> in MapServer
> (from UMN) but it freaks me out that xmin is greater than 
> xmax.  The third
> would normally be taken to define a 358x2 degree square not 
> crossing the 
> equator.  The first is only acceptable if degree values outside the 
> -180 to 180 / -90 to 90 range are allowed and even then we 
> would have to
> carefully consider the semantics. 
> 


This is part of the 1.1 specification, par 6.5.6

----- Quote:

In the particular case of longitude, the following behavior applies
regarding the anti-meridian
at 180 degrees of longitude. There is a legitimate desire for maps that
span the
anti-meridian (for example, a map centered on the Pacific Ocean). If
Xmin is the west-most
longitude in degrees and Xmax is the east-most, then the following
constraint
applies:
-180 <= Xmin < Xmax < 540

EXAMPLES: Xmin,Xmax values and the corresponding scope of the bounding
box:
-180,180 = Earth centered at Greenwich
0,360 = Earth with Greenwich at left edge
120,250 = Pacific Ocean

----- Unquote

Best regards,

Bart Adriaanse
www.demis.nl

[dmorissette]

Not sure how much we can or want to do about this.  Let's revisit in 4.1

[fwarmerdam]

Well, hopefully we can addrses this in 4.5. 

I would also like to refer folks to the document at: 

http://cite.occamlab.com/test_engine/wms_1_1_1/files/WMS_HTML/#basic_elements.params.bbox

This seems to suggest strictly conforming servers would not allow request over 
180 for geographic coordinate systems. 


Perry is also wondering if we could make it possible to tell mapserver
(via metadata) whether the remote server is going to blow a gasket if we go
over 180.  I think we don't now.

[pramsey]

WMS request with 0-360 longitude

[pramsey]

Mapserver accepts longitude > 180, per the optional behavior described in the WMS specification document for anti-meridian crossing. If people want to publish data in that area, they will have to transform their data to also be in 0-360 range, but Mapserver can fit the bill. No fix required.