| Q: /satellite projection in IDL maps [message #2637] |
Sat, 06 August 1994 01:53 |
moersch
Messages: 2
Registered: August 1994
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Junior Member |
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Greetings -
I've recently been playing around with the satellite map projection in
IDL, and I've noticed that the parameters you have to specify seem
very awkward. You supply MAP_SET with the satellite's altitude and
sub-satellite point on the ground, along with two angles for the
direction of viewing - one an azimuthal angle, and the other a cone
angle, measured off of nadir (looking straight down). That all makes
sense to me. But you also need to specify a set of four
latitude/longitude pairs for the top, bottom, and sides of the map
that will be produced. That really seems odd - it's difficult to pick
those limits and not have some points end up over the horizon of the
planet, for example.
It seems to me that a much more intuitive way of determining the
limits of the image/map would be to specify a field of view of the
camera in degrees. Let the computer go off and figure out what that
translates into in lat/lon coordinates, I say! Has anybody by chance
written an IDL program that will do this?
To give a little background, I am working with a mosaic of images of
Jupiter from last month's comet crash. We have reprojected several
images into a cylindrical projection and mosaicked them into a full
map of Jupiter's southern hemisphere. What I'd like to do is be able
to use IDL's mapping routines to project our mosaic so that we could
display Jupiter as it would appear from any arbitrary point in space.
Ideally, I'd want to have a program that takes the subsatellite point,
the satellite altitude, the camera direction, and the camera field of
view, and produce an image of Jupiter as it would appear from that
vantage point.
Any pointers to potentially useful programs out there would be greatly
appreciated!
Thanks for your time.
Jeff Moersch
Astronomy and Space Sciences
Cornell University
moersch@astrosun.tn.cornell.edu
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