Philippe Peeters wrote:
>
> I've already posted this question some time ago but did not get any
> answer. Here I go again:
>
> I want to draw satellite data on a map. Each ground pixel is defined by
> the latitude and longitude of the 4 corners. It is not a regular
> rectangle or square and depend on the viewing geometry of the satellite
> instrument.
> I have tried a simple polyfill,long,lat but I have serious problems with
> orthographic maps when the pixel is partly off the map. I got strange
> filled polygons from the edge of the map to the corner of the window.
> Someone on the net advice me to use a new polyfill routine which checks
> polygons boundaries before drawing it. Though slower than the original
> polyfill, it solved the problem.
This is NOT a perfect solution, but it may give you some
ideas on how to proceed...
;
; Name ............ my_polyfill.pro
;
; Description ..... Before executing polyfill, check that
; the (x,y) coordinates are valid.
;
; Parameters ...... x,y contain vertices of the polygon.
;
; Keywords ........ See documentation for polyfill.
;
; Originator ...... Andrew F. Loughe, NOAA/ERL/CDC, 21 MAY 1996.
pro my_polyfill, x, y, _EXTRA=e
on_error, 2
; Convert the x,y coordinates to the normalized system.
result = CONVERT_COORD(x, y, /data, /to_normal) ; DEFAULT:
From /data
; Check that /normal or /device might be set.
if ( KEYWORD_SET(e) ) then begin
names = TAG_NAMES(e)
for i = 0, N_TAGS(e)-1 do begin
if ( names(i) eq 'NORMAL' ) then $
result = CONVERT_COORD(x, y, /normal, /to_normal) ; From
/normalized
if ( names(i) eq 'DEVICE' ) then $
result = CONVERT_COORD(x, y, /device, /to_normal) ; From
/device
endfor ; i-loop
endif ; KEYWORD_SET(e)
; Check that the normalized coordinates are within the bounds
; set by !x.window and !y.window
out_of_bounds = 0
if ( MIN(result(0,*)) lt !x.window(0) or $
MAX(result(0,*)) gt !x.window(1) or $
MIN(result(1,*)) lt !y.window(0) or $
MAX(result(1,*)) gt !y.window(1) ) then out_of_bounds = 1
if (out_of_bounds eq 1) then print, '(x,y) coordinates are out of
bounds!'
if (out_of_bounds eq 0) then polyfill, x, y, _EXTRA=e
end
> But I still have another problem with several maps when the pixel to be
> drawn is at the edge, i.e. when one or several pixel corner is on one
> side of the map (lon > -180) and the other on the other side (lon< -180)
> of the map.
> example longitude=[-179,-181,-179.5,-180.5] or [179,181,179.5,180.5]
What if you add 360 to your points vector and
make your map go from 180 to 540?
map_set, 0, 360, /cont
Does that work? |
--
Andrew F. Loughe afl@cdc.noaa.gov
University of Colorado, CIRES http://cdc.noaa.gov/~afl
Campus Box 449 phn:(303)492-0707 fax:(303)497-7013
Boulder, CO 80309-0449 "He who laughs last thinks slowest!"
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