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20000327: Plotting isallobars from McIDAS SPC

>From: "Pam Grube" <address@hidden>
>Organization: Lyndon State College
>Keywords: 200003202238.PAA01169 McIDAS-X SPC MDX macro


This is a follow-up to Don Murray's March 27 reply to you concerning
use of the SPC command to plot altimeter setting changes over time
(e.g., isallobars).

You noted:
>>     I tried what you suggested,,,using the DAY= addition to the 
>>command, and it seems to work.

For reference (and for the tracking system files), we did not update
the SSEC-supplied MDX macro commands to check the format of the
DAY key in surface MD files.  The reason we did not was SSEC
has sunset support (i.e., dropped support) for MDX and the macros
that run it.  None of their MDX macro commands (SP, SC, UP, UC) were
Y2Kized.  We have continued to include them in our distribution so
that sites relying on their use had time to switch to use of newer,
ADDE commands that are Y2K capable.

You noted:
>The problem with the SPC 
>>command is that it plots only the whole numbers (one single digit), 
>>and in order to have the students contour and use isallobars, I need 
>>one more significant digit (such as I get with the SP command).  If 
>>the SP command goes away in the future, the SPC command 
>>won't be of much use to me.  (eg. if the program plots a 1, that is 
>>not enough detail.  I need it to plot 13 or 18, or whatever, to tell me 
>>the pressure change has been 1.3 or 1.8 mb/3 hr., so that we can 
>>contour the data properly.  

I checked into this and found the reason that SPC was not plotting
PSL (altimeter setting) differences in tenths of millibars.  I adjusted
the code so that it now does.  The modification to the source code
for SPC, spc.mac, is contained in the McIDAS Addenda that I made
effective 0Z today, March 19.  The URL for McIDAS Addenda is:


Included in this addenda are modifications for other MDX macro commands
that will prevent problems like what Bill Fingerhut was seeing in some
of his BATCH files (i.e., floating point exceptions and McIDAS dying).
I have CCed Bill and Mark Tucker on this message so that they will be
aware of the newly released, bugfixed code.

You noted:
>>Also, on an unrelated matter, do you have at Unidata any 
>>documentation explaining the use of the icons surrounding the new 
>>McIdas image window.  

Don's comment on there not being documentation on the GUI (MCGUI) is
right on the mark:

Don commented:
>Right now, the GUI is under construction (as the icon
>indicates), so while it is in flux, there probably will be little

For the buttons across the top of the GUI, I provided small bubble
helps that basically give one a rough idea about what the button is
supposed to do.  I realize that this may not help the user that is not
familiar with the package as a whole.  This will change as I can get
back to the GUI (which will happen once SSEC provides ADDE versions of
MDX macro routines that have the kind of functionality that you are
using SP for (e.g., parameter differencing, etc.)).

You noted:
>>I hate to admit it, but without 
>>documentation, I can't even figure out how to zoom an image with 
>>the Z icon, as it just zooms the same reframe every time, and there 
>>seems to be no way to control where the center of the zoom is 
>>located (aside from ALT Z, which still just gives you a specific 

With the zoom button, there really is no control over where the center
of the zoom will be.  What you use the zoom for is to blow up the image
by the zoom factor, and then pan the image within the frame viewport.
Panning is accomplished by draging the mouse while holding down the
middle mouse button.  Don's comment about using the ALT-Z keystroke
combination helps, but it doesn't guarantee that the point under the
cursor at the time of the blowup will be the center of the zoom.  By
the way, the zooming works for all frames at the same time.  If you
have a loop of images, pressing the Zoom button will cause all of the
images to zoom.  Draging the mouse with the middle button depressed
will pan all of the images in the loop at the same time.

>>I also can't figure out how to superimpose various fields 
>>using the menu mode.  

I hope that Don's explanation help you out in this regard:

>For plots and contours, you can overlay using the Plot Time Selection
>menu that comes up after you select a parameter (for surface) or level
>(for upper air).  For example, if you wanted to display the latest
>GOES-East IR image using the menu and overlay pressure contours, you would
>Esc - get to Main Menu
>   F1 - Latest Images/Image Loops
>      F2 - GOES-East Infrared  (image will then display).
>Esc - get back to main menu
>   SF2 (shift+F2) - Surface Contours
>      F3 - Sea Level Pressure
>         F3 - Use time of data in current Frame
>If you wanted to select a different time, you could use F2 instead of F3
>in the last step, and select the date/time, but set the map to OLAY
>in the list of maps.

Overlaying using the GUI is accomplished by selecting the Overlay radio
button on the Point Source Plots GUI widget.  In both the Fkey menu and
the GUI, there is an underlying assumption of there being a default map
on top of which "things" are plotted (overlain).  When one plots a
field of anything, the first thing that is done is draw a map followed
by overlay on top of that map.

You noted:
>>     Any help/documentation you can provide would be greatly 
>>appreciated...Mark cannot find anything of assistance in what he 
>>has here, and says it was not really a topic under discussion at the 
>>workshop he and Bill attended. 

We did go over overlaying using both the Fkey menu and GUI, but it was
not dwelled on.

I hope that this helped somewhat.

* Tom Yoksas                                             UCAR Unidata Program *
* (303) 497-8642 (last resort)                                  P.O. Box 3000 *
* address@hidden                                   Boulder, CO 80307 *
* Unidata WWW Service                             http://www.unidata.ucar.edu/*

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