| Re: map_set - 8-element limit [message #12406] |
Thu, 30 July 1998 00:00 |
wmc
Messages: 117
Registered: February 1995
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Senior Member |
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6E69DBEB@ssl.berkeley.edu, Harald Frey <hfrey@ssl.berkeley.edu> writes:
> wmc@bas.ac.uk wrote:
>> map_set,lim=[-65,-180, -65,-90, -65,0, -65,90],/grid,/cont,/iso,/ster,-90
>>
>> ought to work (all pts along 65 S, regularly spaced in longitude)
>> since its a perfectly good square in physical space coordinates.
>>
>> But it doesn't - I get just a single horizontal line and a divide-by-zero.
> For this specific simple problem you should use a 4-elements vector instead
> of the 8-elements. So try
>
> map_set,lim=[-65,-180, -65,180],/grid,/cont,/iso,/ster,-90
What I want to do is to use the 8-element form, and I want it to work whether
the pole is inside the box or not.
The example I've given above can be done other ways. Sure. But *it ought to
work as I've given it*. It doesn't. Why not?
Does anyone out there have experience of using the 8-element form,
preferrably with a /ster projection?
- William
---
William M Connolley | wmc@bas.ac.uk | http://www.nbs.ac.uk/public/icd/wmc/
Climate Modeller, British Antarctic Survey | Disclaimer: I speak for myself
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| Re: map_set - 8-element limit [message #12413 is a reply to message #12406] |
Wed, 29 July 1998 00:00  |
Harald Frey
Messages: 41
Registered: March 1997
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Member |
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wmc@bas.ac.uk wrote:
> Hello group...
>
> I'm having trouble (idl 5.1; alpha) with map_set limits for 8-element
> vectors.
>
> map_set,lim=[-65,-180, -65,-90, -65,0, -65,90],/grid,/cont,/iso,/ster,-90
>
> ought to work (all pts along 65 S, regularly spaced in longitude)
> since its a perfectly good square in physical space coordinates.
>
> But it doesn't - I get just a single horizontal line and a divide-by-zero.
For this specific simple problem you should use a 4-elements vector instead
of the 8-elements. So try
map_set,lim=[-65,-180, -65,180],/grid,/cont,/iso,/ster,-90
and this gives you probably what you want.
Harald Frey
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| Re: map_set - 8-element limit [message #12420 is a reply to message #12413] |
Wed, 29 July 1998 00:00 |
wmc
Messages: 117
Registered: February 1995
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Senior Member |
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1027cc2b682ba60989819@news.frii.com, davidf@dfanning.com (David Fanning) writes:
> William Connelly (wmc@bas.ac.uk) writes:
>> map_set,lim=[-65,-180, -65,-90, -65,0, -65,90],/grid,/cont,/iso,/ster,-90
>>
>> ought to work (all pts along 65 S, regularly spaced in longitude)
>> since its a perfectly good square in physical space coordinates.
> I'm confused. How can points that line along a line on a map
> surface be a square in physical space coordinates?
I've set /ster, so I should be getting a polar stereographic projection.
Thus the points are:
-65,0
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-65,-90 -----+----- -65,90
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-65,-180
Of course, if you think about the points in a lat-lon projection, then they are
in a straight line.
- William
---
William M Connolley | wmc@bas.ac.uk | http://www.nbs.ac.uk/public/icd/wmc/
Climate Modeller, British Antarctic Survey | Disclaimer: I speak for myself
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| Re: map_set - 8-element limit [message #12424 is a reply to message #12413] |
Tue, 28 July 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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William Connelly (wmc@bas.ac.uk) writes:
> I'm having trouble (idl 5.1; alpha) with map_set limits for 8-element
> vectors.
>
> map_set,lim=[-65,-180, -65,-90, -65,0, -65,90],/grid,/cont,/iso,/ster,-90
>
> ought to work (all pts along 65 S, regularly spaced in longitude)
> since its a perfectly good square in physical space coordinates.
I'm confused. How can points that line along a line on a map
surface be a square in physical space coordinates? At least
if we mean by "physical space coordinates" a portion of the
sphere's surface.
The LIMIT keyword is suppose to delineate a portion of the
map surface to display, not an oblique slice through a
3D sphere.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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