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Re: Map Projections [message #69506 is a reply to message #69371]

Mon, 18 January 2010 09:28

Juggernaut
Messages: 83
Registered: June 2008

Member

On Jan 15, 3:52 pm, David Fanning <n...@dfanning.com> wrote:
> Bennett writes:
>> I currently have data with an associated latitude and longitude
>> frame. I've seen David Fanning's "Navigating GOES Images" example but
>> the process does not seem to work for my data.
>> When I say it does not work the resulting projection results in
>> showing much less of the data than it should based on the lat/lon
>> limits.
>
> How are you choosing the "limits"? These are not necessarily
> the corners of your image.
>
>> Does the data inherently have to be North up and east/west going right/
>> left? My data is presented in an orientation where North is at an
>> angle as are the other directions where the bottom of the image is not
>> lowest latitude etc... Is there a special way to handle the
>> projection for these types of datasets?
>
> No, pick the upper-left corner of the rectangular image as your
> starting point, and you should be good to go. What kind of map
> projection is this, what is the lat/lon in the upper left corner,
> what size is your image in pixels, and what is the resolution of
> a pixel in meters? (You *can* determine the later number from
> the lat/lon corners of your image.)
>
>> The end result I'm looking for is a GeoTiff. I would think that with
>> all this information at my fingertips IDL would make this easy but
>> alas it is not.
>
> You have been reading WAY too many marketing materials. :-)
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")

I am currently simply following your example and selecting the middle
left, top, right and bottom as my limits. I should probably be doing
a different calculation to retrieve these points since I don't have
the nicely oriented data. Poor map projection knowledge = rough road.

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[Message index]

		Map projections By: James Kuyper on Mon, 12 November 2001 07:55
		Re: map projections By: jeffnettles4870 on Wed, 13 February 2008 14:04
		Re: Map Projections By: David Fanning on Fri, 15 January 2010 13:12
		Re: Map Projections By: Juggernaut on Mon, 18 January 2010 05:16
		Re: Map Projections By: David Fanning on Fri, 15 January 2010 12:52
		Re: Map Projections By: Juggernaut on Mon, 18 January 2010 09:28
		Re: Map Projections By: Juggernaut on Mon, 18 January 2010 11:00
		Re: Map Projections By: David Fanning on Mon, 18 January 2010 09:41

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