On Saturday 21 July 2007 14:26:27 Brent Wood wrote: > --- "A.Th.C. Hulst" <[EMAIL PROTECTED]> wrote: > > Hello, > > > > I wondered if it is possible to get mapserv as far as showing a map from > > [-180 > > 180> while to original dataset is [0 360>. My attempts only show data > > from [0 180>. > > It will show data from -180 t0 o if you scroll left enough. > > There is no way to do this easily. I use a PostGIS table with two geometry > columns, one in each longitude space. Points are easy to convert, but lines > & polygons that cross 180 need to be joined/merged while those that cross 0 > need to be split. So it is not just a simple reprojection, but als includes > a merging or splitting of affected features crossing the 0/180 meridians. > > I also achieve the same result by cutting the wester hemisphere of data, > translate it by 360 degrees & paste it onto the 0-180 geometry column, so > the column goes from 0-360, 1 1/2 times around, which gives a reasonably > seamless map at the cost of some redundant data. > > I have found a few ways with PostGIS to work around this problem, but no > simple solutions. > > Raster data is also a problem, under Linux a symlink to tiles in the > eastern hemisphere with accomapnying world files seems to work OK, so there > is a -180 to 360 cover, without replicating images or tiles, just the extra > world files. > > > That relates a bit to my next wish; can mapserver zoom cyclic? When I > > zoom in > > > > on 360, I want to see data from 320 to 360(-dx) and 0 to 40 degrees. Is > > this possible with current implementations? > > As above, yes, if your dataset is -180 to 360. I was afraid that this was the answer ;)
My hope was that I didn't need to fiddle with the data as I have a fresh dataset every 6 hours. Ah well.... Thanks. > > > Cheers, > > Brent Wood > > > Regards, > > Sander
