| Huge Maps & a device for faking a large window [message #38845] |
Wed, 31 March 2004 12:02 |
JD Smith
Messages: 850
Registered: December 1999
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Senior Member |
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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
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