| Re: mapping data & grid (MAP_SET MAP_GRID) [message #18693 is a reply to message #18691] |
Thu, 03 February 2000 00:00  |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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Ken Mankoff wrote:
> Wow, sorry to you all for the poorly worded statement (it turns out there
> wasn't even a question at the end of it all). Its been a long day of
> school and IDL commands that won't do what i want.
>
> So, the question is: Does anyone out there know how to do the following:
>
> thanks again,
> ken.
>
> On Wed, 2 Feb 2000, Kenneth Mankoff wrote:
>
>> Hi all,
>> i'm making global images, with grids, according to the following
>> instructions:
>>
>> 1. draw the globe on the screen so that the _geomagnetic_ pole is
>> centered.
>> 2. draw the grids according to the _geographic_ poles.
>>
>> The code i use is the following:
>> ;;; data is a 2d array, sorted on latitude and longitude.
>> ;;; the geomagnetic pole in the north is at (82, -90), for 1999.
>> MAP_SET, 82, -90, /ortho
>> img = MAP_PATCH(data, xstart=xx, ystart=yy, lon0=lon0, lon1=lon1)
>> TV, img, xx, yy
>> MAP_GRID ;;; <--- ERROR!!
>>
>> This map_grid puts the grid centered on the pole of the data. The pole i
>> want to center it on is different, due to the different coordinate
>> systems.
>>
>> A new map_set to change the coordinates will not work, because the
>> map_grid erases the screen after a map_set
>>
>> I have tried plotting to the Z-buffer, reading it, and re-displaying it to
>> X, but TV does not have a NO_ERASE keyword as far as i can tell, so the
>> data part of the image gets erased again.
Ken,
I guess I'm not following your train of thought. According to your
instructions, the map projection should be centered at the geomagnetic north
pole (82, -90):
map_set, 82, -90, /ortho, /isotropic
Then you want to display a grid registered to the geographic north pole:
map_grid
If you forget about the mapped image for the moment, is this the result you
want?
Cheers,
Liam.
http://cimss.ssec.wisc.edu/~gumley
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