orthographic projection

[Patrick Joeckel <joeckel@xxxxxxxxxxxxxxxxx>]

Dear Ferreters,

below I included a script which uses the orthographic projection for plotting
data. Two problems occur:
 1) go mp_land plots the map on top, however with a gap where the underlying
     lon-axis (defined with modulo) wraps around
 2) the interpolation with "fill" exhibits a discontinuity at the same meridian
     (take a look over Europe !!!)   
  
Are these problems known to anyone, and does possibly a workaround exist ?
Hope anybody can help me !

Best regards ...
          Patrick Joeckel

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cancel data/all
cancel variable/all
cancel region

define axis/x=1.875:358.125/npoints=96/unit=lon/mod xax
define axis/y=-90:90:10/unit=lat yax
define grid/x=xax/y=yax g2d

let one = x[gx=xax]+y[gy=yax]
let data = COS((5*x[gx=xax]/180)*3.1415+1)*SIN((Y[gy=yax]/180)*3.1415)

ppl shaset 0 100 100 100

set grid g2d
go mp_orthographic 0 90
go mp_aspect

fill data*mp_mask, x_page, y_page

go mp_graticule 0 360 10 -90 90 30 5

go mp_land 13 " " 1 1

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Patrick Joeckel
Max Planck Institute for Chemistry
Joh.-J. Becher Weg 27         
55128 Mainz                   phone:++49-6131-305452      
Germany                       fax  :++49-6131-305436     
                             e-mail:joeckel@mpch-mainz.mpg.de
                         http://www.mpch-mainz.mpg.de/~joeckel
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Never trust an operating system you don't have sources for.