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20000314: GEMPAK and satellite zooming

>From: David Ovens <address@hidden>
>Organization: .
>Keywords: 200003142021.NAA13569

>Hello,
>
>I've checked the archives and have not found out how to zoom a GOES-10
>(west coast) satellite image in GPMAP so that the left and right top
>edges of the display are off the planet.  Using garea = dset works
>fine, of course, displaying the planet's limb on both edges and it
>also works in GARP to zoom.  But in GPMAP, "cursor garea" and anything
>else I try fails, basically, because that upper left corner is out of
>bounds in lat/lon space (e.g., cursor garea gives something like
>29.3;179.6;-9999.0;-9999.0).
>
>I've gone as far as looking into imisub.f, hoping to be able to get
>away from lat.s/lon.s to use another coordinate system, such as pixel
>location in the satellite image.  So, I am willing to modify code as
>appropriate, obviously someone figured a way to do it in GARP.
>
>Is there a way that I haven't figured out yet to do this in GPMAP?  Is
>there anyone working on this feature for release 6?
>
>Thank you for any help and information,
>
>David
>-- 
>
>David Ovens            e-mail: address@hidden
>(206) 685-8108
>Dept of Atmospheric Sciences, Box 351640
>University of Washington 
>Seattle, WA  98195
>


David,

Garp gets around the problem by loading the entire image into a shadow buffer
and then displaying the portion of the pixels within the view window.
In effect, you are in graphic coordinates rather than lat/lon coordinates
which is why Garp is displaying the XY cursor location.

NMAP has a similar feature called "roaming" where a "panning" icon is used to 
display a viewport of a larger image (this allows the user to roam within
an image without having to unzoom and zoom into a different region).

The "cursor garea" zoom does not work as you mention because the lat/lon
points in space are not defined.

With Gini images, the Gempak program sector will allow the user to create a
new region by sampling the data region directly. Unfortunately, sector
does not support area files. To do that, you have to use McIDAS to
write a new AREA file of the portion of the AREA file you need.

Steve Chiswell