| Re: Cylindrical map projection screwed up? [message #13518] |
Fri, 13 November 1998 00:00 |
Jonathan Joseph
Messages: 69
Registered: September 1998
|
Member |
|
|
ISOTROPIC keyword was set, though even if it were not,
I would still expect lines of longitude to be vertical
and lines of latitude to be horizontal, the only
difference without ISOTROPIC set should be that the
number of pixels in X degrees of longitude could then
be different than the number of pixels in X degrees of
latitude.
David Fanning wrote:
>
> Are you missing the ISOTROPIC keyword?
>
|
|
|
|
| Re: Cylindrical map projection screwed up? [message #13519 is a reply to message #13518] |
Fri, 13 November 1998 00:00  |
Jonathan Joseph
Messages: 69
Registered: September 1998
|
Member |
|
|
Hmmm.
It looks like this could be it. I had switched from a different
type of map projection and didn't look closely at those
numbers. I had been setting them to be the middle of the
range of latitude/longitude that I was looking at. However,
I'm not sure I understand what meaning they could have in
a cylindrical projection.
Thanks.
-Jonathan
Liam Gumley wrote:
>
> Jonathan Joseph wrote:
>> I've been doing some stuff using cylindrical map
>> projections using set_map. So, darn it, I expect
>> my lines of longitude to be vertical, and my lines
>> of latitude to be horizontal in the image.
>>
>> But, when I set the LIMIT keyword to just look
>> at a small portion of the globe, this is not
>> the case. In fact, I only get a true cylidrical
>> projection if the min and max latitude have the
>> same magnitude, ie. -30 to 30 degrees.
>
> Try this:
>
> map_set, 30, -80, limit=[20,-100,40,-60], $
> /cyl, /isot, /cont, /grid ; Bad result
>
> map_set, 0, -80, limit=[20,-100,40,-60], $
> /cyl, /isot, /cont, /grid ; Good result
>
> Cheers,
> Liam.
>
> ---
> Liam E. Gumley
> Space Science and Engineering Center, UW-Madison
> 1225 W. Dayton St., Madison WI 53706, USA
> Phone (608) 265-5358, Fax (608) 262-5974
> http://cimss.ssec.wisc.edu/~gumley
|
|
|
|
| Re: Cylindrical map projection screwed up? [message #13521 is a reply to message #13518] |
Fri, 13 November 1998 00:00 |
Liam Gumley
Messages: 473
Registered: November 1994
|
Senior Member |
|
|
Jonathan Joseph wrote:
> I've been doing some stuff using cylindrical map
> projections using set_map. So, darn it, I expect
> my lines of longitude to be vertical, and my lines
> of latitude to be horizontal in the image.
>
> But, when I set the LIMIT keyword to just look
> at a small portion of the globe, this is not
> the case. In fact, I only get a true cylidrical
> projection if the min and max latitude have the
> same magnitude, ie. -30 to 30 degrees.
Try this:
map_set, 30, -80, limit=[20,-100,40,-60], $
/cyl, /isot, /cont, /grid ; Bad result
map_set, 0, -80, limit=[20,-100,40,-60], $
/cyl, /isot, /cont, /grid ; Good result
Cheers,
Liam.
---
Liam E. Gumley
Space Science and Engineering Center, UW-Madison
1225 W. Dayton St., Madison WI 53706, USA
Phone (608) 265-5358, Fax (608) 262-5974
http://cimss.ssec.wisc.edu/~gumley
|
|
|
|
| Re: Cylindrical map projection screwed up? [message #13524 is a reply to message #13518] |
Fri, 13 November 1998 00:00 |
davidf
Messages: 2866
Registered: September 1996
|
Senior Member |
|
|
Jonathan Joseph (jj@scorpio.tn.cornell.edu) writes:
> I've been doing some stuff using cylindrical map
> projections using set_map. So, darn it, I expect
> my lines of longitude to be vertical, and my lines
> of latitude to be horizontal in the image.
>
> But, when I set the LIMIT keyword to just look
> at a small portion of the globe, this is not
> the case. In fact, I only get a true cylidrical
> projection if the min and max latitude have the
> same magnitude, ie. -30 to 30 degrees.
>
> Is this a bug? or am I missing something obvious.
Are you missing the ISOTROPIC keyword?
Cheers,
David
----------------------------------------------------------
David Fanning, Ph.D.
Fanning Software Consulting
E-Mail: davidf@dfanning.com
Phone: 970-221-0438, Toll-Free Book Orders: 1-888-461-0155
Coyote's Guide to IDL Programming: http://www.dfanning.com/
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
