| map_set, contour, path_filename norm to lon,lat coord [message #11688] |
Sun, 10 May 1998 00:00 |
mckie
Messages: 3
Registered: September 1994
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Junior Member |
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After using MAP_SET and then CONTOUR to draw contour lines on a map
projection, I am trying to find a reasonable way to obtain lists of
longitude and latitude coordinates along the contours that were drawn.
Calling CONTOUR a second time with the PATH_FILENAME options gives
normalized coordinates along all contour lines. (The PATH_INFO and
PATH_XY options to CONTOUR do not seem to work well, because they
apparently only return info about closed contours. Using the /CLOSED
option to CONTOUR makes things worse with stray contour lines crossing
the center of the plot from the extreme boundaries.)
)
So the less efficient PATH_FILENAME option to CONTOUR generates an
unformatted file with all the normal coodinates, and I can then input
this info. But how do I then convert these lists of normalized
coordinates to longitude and latitude for the projection as specified
in the most recent call to MAP_SET?
The CONVERT_COORD routine does not seem to do the job, as a request to
convert from normalized TO_DATA results in normalized coordinates.
There are hints in various idl documentation that the !MAP system
variable may be involved, but I have been unable to locate any
details about how to use !MAP to convert normal coord back to lon
lat in a general way for any projection.
Does a NORMAL_TO_LON_LAT routine exist for use after a call to MAP_SET?
I'm hoping to use this with !P.MULTI for multiple maps on each frame,
so I am guessing it needs to handle normalized coordinates relative to
the entire frame, and not relative to the frame subset for each map.
Thanks
Bill McKie
Sterling Software
NASA Ames Research Center
mckie@sky.arc.nasa.gov
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