| Irregularly Lat Lon Grid: Displaying Land Types [message #40879] |
Mon, 13 September 2004 09:48  |
alonge
Messages: 4
Registered: September 2004
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Junior Member |
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Hello all,
I have vegetation type data (Integer 1-13) on a 12km grid and
would like to display it on a map. I don't want to contour the data
but rather just display the grid boxes colored according to the
vegetation class. I can't use map_image (not a regular lat/lon grid).
Any ideas or suggestions will be greatly appreciated.
Running IDL 5.4 on SGI IRIX
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| Re: Irregularly Lat Lon Grid: Displaying Land Types [message #40968 is a reply to message #40879] |
Mon, 20 September 2004 12:07  |
K. Bowman
Messages: 330
Registered: May 2000
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Senior Member |
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In article <fd11a4c5.0409201045.719a894f@posting.google.com>,
alonge@atmos.albany.edu (Thundurstruck) wrote:
> The grid is output from NCEP's operational ETA forecast model on the
> Arakawa (rotated lat-lon) E-grid. The grid is staggered row by row,
> rotating wind and mass points, giving the the data a diamond type grid
> box.
>
> Here is a short example
>
> H V H V H V
> V H V H V H
> H V H V H V
>
> The grid is 606 in E-W or x direction and 1067 in the N-S or y
> direction.
>
> The SW corner is located at 3.441S , 148.799 W
> and the NW corner is located at 50.000N , 111.000 W
>
> Thanks,
> Chuck
If you know the lats and lons of the corners of the boxes, you can use
POLYFILL to draw polygons for each grid cell on any map projection.
IDL> map_set, /cont
IDL> polyfill, [0.0, 10.0, 20.0, 10.0, 0.0], [0.0, 10.0, 0.0, -10.0,
0.0], color = ...
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| Re: Irregularly Lat Lon Grid: Displaying Land Types [message #41033 is a reply to message #40879] |
Thu, 16 September 2004 00:54 |
Klaus Scipal
Messages: 45
Registered: November 1997
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Member |
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In principle it depends on the grid you use. In global remote sensing for
example, irregular grids are in fact often the product of a sinusoidal
projection, i.e the number of gridpoints decreases with latitude to get
equally sized cells.
Anyway, a quick and dirty way of doing the plotting is to define a
usersymbol which is a filled circle and then use plots with the color
keyword. Color must have the same size as your lon,lat files and it should
contain the colorcodes of the parameter you want to display.
The code might look as follows
a=Findgen(32)*!pi/16.
r=0.1
UserSym,r*cos(a),r*sin(a),/Fill ; define a usersymbol which is a circle and
has the radius r
Plots,lon,lat,Psym=8,Color=color
regards
Klaus
"Thundurstruck" <alonge@atmos.albany.edu> wrote in message
news:fd11a4c5.0409130848.5fbf26c4@posting.google.com...
> Hello all,
>
> I have vegetation type data (Integer 1-13) on a 12km grid and
> would like to display it on a map. I don't want to contour the data
> but rather just display the grid boxes colored according to the
> vegetation class. I can't use map_image (not a regular lat/lon grid).
> Any ideas or suggestions will be greatly appreciated.
>
> Running IDL 5.4 on SGI IRIX
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