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Re: More Map Projection Madness [message #78302 is a reply to message #78215]

Fri, 04 November 2011 10:34

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

> What is wrong with the right side of this Equirectangular
> map projection?
>
> IDL> m = map_proj_init(117, datum=19, /gctp)
> IDL> map_grid, map_structure=m, linestyle=0
> IDL> map_continents, map_structure=m
>
> There seem to be extra lines at odd angles at
> the top and bottom of the map on the right-hand
> side.

As I have received no answer, I thought perhaps my
example wasn't working. Here is code that reliable
shows the problem I am having with map projections.
In particular, when I set up the projection with
Map_Proj_Init and try to draw grid lines, I am
getting extraneous and ill-positioned lines showing
up on the plot. If you look at the right-hand side
of the third window, you can see an example of
what I mean.

;**********************************************************
lons = -180 > Indgen(11)*36-180 < 180
lats = -90 > Indgen(11)*18-90 < 90
window, 0, Title='Normal Map Grid'
map_set, /Cylindrical, Position=[0.1, 0.1, 0.9, 0.9]
map_grid, lats=lats, lons=lons

window, 1, Title='OK GCTP Map Grid'
m = Map_Proj_Init('Miller Cylindrical', Datum='Sphere', /GCTP)
plot, [0,1], xrange=m.uv_box[[0,2]], yrange=m.uv_box[[1,3]], $
xstyle=5, ystyle=5, /noerase, /nodata, $
Position=[0.1, 0.1, 0.9, 0.9]
map_grid, lats=lats, lons=lons, map_structure=m

window, 2, Title='Screwed Up GCTP Map Grid'
m = Map_Proj_Init('Cylindrical')
plot, [0,1], xrange=m.uv_box[[0,2]], yrange=m.uv_box[[1,3]], $
xstyle=5, ystyle=5, /noerase, /nodata, $
Position=[0.1, 0.1, 0.9, 0.9]
map_grid, lats=lats, lons=lons, map_structure=m
END
;**********************************************************

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: More Map Projection Madness By: David Fanning on Thu, 03 November 2011 11:43
		Re: More Map Projection Madness By: David Fanning on Tue, 01 November 2011 13:20
		Re: More Map Projection Madness By: David Fanning on Tue, 01 November 2011 11:02
		Re: More Map Projection Madness By: chris_torrence@NOSPAM on Tue, 01 November 2011 10:30
		Re: More Map Projection Madness By: David Fanning on Tue, 01 November 2011 10:32
		Re: More Map Projection Madness By: David Fanning on Tue, 01 November 2011 09:35
		Re: More Map Projection Madness By: Paul Van Delst[1] on Mon, 07 November 2011 08:19
		Re: More Map Projection Madness By: David Fanning on Fri, 04 November 2011 10:34

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