| Re: "TRUE" map projections [message #3425] |
Wed, 25 January 1995 05:19 |
zawodny
Messages: 121
Registered: August 1992
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Senior Member |
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In article <3g3rod$rpp@lace.Colorado.EDU> afl@bjerknes.cdc.noaa.gov (Andy Loughe) writes:
> How can one obtain (for example) a "true" Mercator map
> projection in IDL? Sounds rather academic, doesn't it?
...
> There must be a single, proper aspect ratio for
> a map to be called a "true" Mercator projection. Is IDL capable
> of producing "true" map projections, or is one able to arbitarily
> re-shape the projection into any form he wishes such that the
> specification of the projection is all but pointless? Does one
> simply say "hmmmm, looks good to me" and move onto the next task?
I definitely fall into the "looks good enough to me" catagory. Where ever
possible I use "circular" map projections and the SET_ISOXY routine. But,
as you point out, there is no such fool-proof method for doing a similar
thing with non-circular maps. It would be very nice/useful/important to
have a keyword (eg. /true or /auto_aspect) for map_set. Adjusting these
maps manually is a real pain because it requires an intimate knowledge of
the proper aspect ratio of a map of the full globe (where allowed or
appropriate) and the coordinate transformation. Since IDL already "knows"
this information it seems reasonable that it could/should do this
calculation for the user.
Speak and be heard.
--
Joseph M. Zawodny (KO4LW) NASA Langley Research Center
Internet: j.m.zawodny@larc.nasa.gov MS-475, Hampton VA, 23681-0001
TCP/IP: ko4lw@ko4lw.ampr.org Packet: ko4lw@n4hog.va.usa.na
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