20010417: Global Mollweide questions

>From: Edward Hindman <address@hidden>
>Organization: CCNY
>Keywords: 200104171531.f3HFV7L24721 McIDAS IMGCOPY MAP mollweide

Ward,

>We are using Global Mollweide imagery to study thunderstorms in Nepal.  
>Nepal appears small in these 32 km-resolution images.  Thus, we are 
>attempting to magnify them X2.   However, we are unable to magnify 
>the images using the IMGCOPY command.  We are, however, able to magnify 
>the 8 km-resolution GOES images X2 with the IMGCOPY command.  What are we 
>doing wrong?

You may be comparing the "look" of the global Mollweide IR image with
that of the GOES images in the Unidata-Wisconsin broadcast.  The GOES
images in the broadcast have 4 km resolution.  The Fkey menu loads
them with a 2x blowdown, a procedure that makes them look like they
have 8 km resolution.  The Mollweide images, on the other hand, are
loaded at their full resolution through the Fkey menu.

If one loads one of the GOES images from the Fkey menu using the
"User-definded load" (SF12), and chooses Line and Element
blowup/blowdowns of 1, the image will be loaded at its primary
resolution.  In order to blowup the Mollweide image (i.e., to make a
smaller earth area take up more of the display), you would have to load
using a blowup of 2, 3, 4, etc.  Again, you will not see more
information since the image is small to begin with.

>Further, when we use the MAP H command to put a map on our Mollweides 
>which are displayed using the IMGDISP command, only the USA is mapped.

'MAP H' means to draw a High resolution map over the image.  High
resolution (and Very High (VH) resolution) maps are only available over
the continental US.

>However, when we display the Mollweides using 
>the F-Key menu, a world map appears.

The Fkey menu is essentially doing a:

MAP SAT

This draws a medium resolution map over the image.

>Could you please teach us how to 
>put that world map on the Mollweide's we display manually using the 
>IMGDISP command.

Here is what I would do:

IMGDISP RTIMAGES/MOLL-IR LATLON=30 -92 MAG=4 EU=IMAGE REFRESH='EG;MAP X 5 
FILE=OUTLHPOL;MAP SAT 1'

(this is one long line, not two)

This will display the current global Mollweide IR image centered on
30N,92E blownup by a factor of 4 using the IMAGE enhancement.  The
REFRESH= keyword sequence will erase all graphics from the frame and
then draw two maps:  political boundaries in color 5 (red) and
land/water boundaries in color 1 (magenta).

The above invocation is equivalent to:

IMGDISP RTIMAGES/MOLL-IR LATLON=30 -92 MAG=4 EU=IMAGE
EG
MAP X 5 FILE=OUTLHPOL
MAP SAT 1

As far as IMGCOPY goes, the reason it is not working for you is that
the resolution set in the header of the Mollweide images incorrectly is
set to 1 km.  IMGCOPY will complain saying that it can not blow up an
image if its resolution is already 1 km.  I am not quite sure why
IMGCOPY is preventing this.  I will have to chat with SSEC to find out
the real reason.

>Thank you.

You are welcome.

Tom Yoksas