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Re: Huge Maps & a device for faking a large window [message #38825]

Thu, 01 April 2004 05:55

Jack Saba
Messages: 30
Registered: January 1996

Member

JD Smith wrote:

>
> Any makers of large map projection images here? I'm having a
> conceptual problem creating a very large (~1Gpix) projected image. I
> bin a large data set into small bins tiling the entire range of
> latitude and longitude (43200x21600). I do this in a series of
> "tiles" to avoid working with the entire data set at once. So far so
> good. If I then want to warp this image to a given projection (like
> Aitoff), it seems I must first use MAP_SET to specify the projection
> details, *and* have a window open of the desired output size. The
> problem is, I have no intention of actually displaying the projected
> image (too large!), so all of the memory allocated for creating that
> big window is wasted (which is more than a nuisance when building such
> huge images).
>
> Unfortunately, MAP_PATCH (possibly via an undocumented keyword to
> TRIGRID -- MAP) and MAP_IMAGE (via CONVERT_COORDS) rely on a presently
> set window to dictate the size of the projected image. If
> TRIGRID(MAP=) were documented, perhaps I could do this myself, but it
> seems likely it also internally consults the current window to set the
> size for the coordinate transform. I see two ways out:
>
> a) Does anyone know of a way to access the mapping transformations
> directly (aside from re-coding them yourself), independent of any
> particular window geometry? Why shouldn't I be able to perform an
> arbitrary coordinate transformation using one of the many mapping
> transforms MAP_SET offers? Coupling this to a specific display
> device size is an unnecessary limitation.
>
> b) Barring this, is there a device in which a window can be
> established which does not consume any memory or accept display
> commands, but simply provides a dummy framework from which
> CONVERT_COORDS etc. can take window info?
>
> Thanks,
>
> JD
>

If the problem is space, what about postscript mode with filename='/dev/null'?
Assuming you are on a unix system, of course.

Jack Saba
--
jack / saba at gsfc / nasa / gov

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[Message index]

		Re: Huge Maps & a device for faking a large window By: Jack Saba on Thu, 01 April 2004 05:55
		Re: Huge Maps & a device for faking a large window By: JD Smith on Wed, 31 March 2004 15:38
		Re: Huge Maps & a device for faking a large window By: Liam Gumley on Wed, 31 March 2004 13:59
		Re: Huge Maps & a device for faking a large window By: Michael Wallace on Wed, 31 March 2004 13:09
		Re: Huge Maps & a device for faking a large window By: btt on Wed, 31 March 2004 12:46
		Re: Huge Maps & a device for faking a large window By: dmarino on Thu, 01 April 2004 13:13

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