| Re: google earth projections [message #63293 is a reply to message #63180] |
Tue, 04 November 2008 07:42   |
liamgumley
Messages: 74
Registered: June 2005
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Member |
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On Nov 3, 6:42 pm, "R.G. Stockwell" <notha...@noemail.com> wrote:
> <liamgum...@gmail.com> wrote in message
>
> news:2f8cf74c-b86f-4ece-bb13-694bf3badde3@n1g2000prb.googleg roups.com...
> On Nov 1, 2:20 pm, "R.G. Stockwell" <notha...@noemail.com> wrote:
>
>
>
>> Does anyone know the IDL map projection to use to make a
>> ground overlay in a kml file (to be viewed by a geobrowser such
>> as google earth?)
>
>> I've googled and have seen many different things stated,
>> so I am not sure if my use of cylindrical projection is right.
>
>> My figures are off, in that my continents do not match earth's continents
>> I am initiallty making a full globe image (-90 to 90 lat , -180 to 180
>> lon)
>> similar to the big blue marble example.
>
>> http://www.gearthblog.com/blog/archives/2006/11/blue_marble_ time_ani....
>
>> but my image of the global map, does not reproduce the continents like
>> in those
>> images.http://mw1.google.com/mw-earth-vectordb/kml-samples/b mng12/files/BMNG...
>
>> cheers,
>> bob
>> This is the projection used by Google Earth overlays:
>> http://en.wikipedia.org/wiki/Plate_carre_projection
>
> Thanks Liam,
> one problem is in converting from the uv coords in the plot window,
> (which range from -2*10^7 to 2*10^7, and -1*10^7 to 1*10^7).
> to my data coordinates that my data is in (drawing polygons in lat and lon).
> Where do i get the info for that coordinate transformation?
>
> I can overlay the continents nicely, and grid and label it, perhaps I just
> have to dig into those routines to see how they do it.
>
> Cheers,
> bob
Bob,
MAP_PROJ_FORWARD converts from lon,lat to x,y
MAP_PROJ_INVERSE converst from x,y to lon,lat
Both of these routines require a map structure variable from
MAP_PROJ_INIT.
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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