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20050706: output of TEMP values in AXFORM (cont.)



>From: "Mekonnen Gebremichael" <address@hidden>
>Organization: Pratt School of Engineering, Duke University
>Keywords: 200504201601.j3KG1gv2005753 McIDAS probing image values

Hi Mekonnen,

>The two images that I sent you earlier were identical - I realized I made a
>mistake. I have rectified this mistake, and also did some analyses as per
>your suggestion. Here is a summary of the results:-

OK.

>RECALL - What I really need is the data over a window a window bounded by
>(25 N - 43 N ; 105 W - 90 W), and re-gridded it at 0.1 degree resolution.
>This is being a challenge.

OK, I finally know what it is your are trying to accomplish.  And, I
assume that you want it in a rectilinear (lat,lon) projection?  All of
this is possible in McIDAS.

By the way, the images you sent are a little odd.  I am unable to view
the recent ones in Mozilla Firefox 1.0.4 either on Linux (Fedora Core
4, 32-bit) or Windows (XP SP2).  I am, however, able to view them using
the image viewer that comes with FC4 and with 'xv'.  I don't understand
this situation.

>1) First, I printed the entire image (i.e. without cutting out the image in
>mcidas). (see original.jpeg)

OK.  This image looks good.

>2) Second, from the image original.jpeg, I cut out the above window and
>re-sampled it at 0.1-degree resolution, using the program I wrote in IDL. I
>used the '.LAT', and '.LON' files to perform this. The result is
>'subset-from-original.jpeg'. (as you see there are series of rings).

OK.  Yes, I see there are a series of rings.  This is what I was
commenting about in my previous email.  This is an artivact of the
resampling.

>3) Next, I cutout a subset of the image from mcidas using these options
>LATLON = 45 117 SIZE=330 720 PLACE=ULEFT. I checked the resulting ascii
>files and this subset covers my entire window. The resulting image is:
>'subset-from-mcidas.jpeg'. Looks good

OK.

>4) Since I want the data at 0.1-degree resolution, I resampled the above
>image (3) to 0.1-degree resolution. The resulting image is:
>'subset-from-mcidas-resampled.jpeg'. This image contains series of rings.

OK.  Again, the rings are an artifact of the resampling.

>In SUMMARY: The problem seems to be in trying to re-grid the data at
>0.1-degree resolution from the GOES data that comes with GOES projection -
>as you pointed out.

I agree.

>The question is: (1) What is the solution?

I would use McIDAS to remap (using IMGREMAP) the original image
specifying the desired output RESolution (RES= keyword) and projection
(PRO=RECT keyword sequence).  IMGREMAP allows you to remap the portion
of the original image you are interested in in the same manner as
IMGCOPY.  IMGREMAP should enable you to get the the areal coverage
you desire; this might take a bit of playing around to get the exact
coverage.  NB: if the portion of the original image you are remapping
lies close to the Earth edge, you may need to include the SSIZE=ALL
keyword sequence.  I would first try without specifying SSIZE, however.
IMGREMAP works in the same way as IMGCOPY:

image in original dataset -> image in output dataset

>The problem I
>had with the previous dataset (GOES composite IR images) was that it comes
>at 13 km resolution, while the current dataset comes with ~4 km resolution.

I understand.  It seems to me that you really need the full resolution
GOES imagery.  Are all of your studies 'historic' (i.e., not realtime)?

>(2) Can MCIDAS provide a solution?,

Yes.  In fact, McIDAS can do everything you have done so far including
the bits done with IDL.

>(3) What do you think is the best way to overcome this?

IMGREMAP.

>Thanks much,

No worries.

Cheers,

Tom
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