BBOX that crosses dateline
|Reported by:||warmerdam||Owned by:||dmorissette|
> 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
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