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[McIDAS #RDQ-637778]: Re: New Questions Regarding My Research

Hi Rod,

> Oh and one more thing.....
> I am still trying to figure out how to do this part:
> How do I find the reflection angle of visible and effective radius?

I think you mean solar zenith angle.

There is no routine in core McIDAS that outputs solar zenith angle
for individual points or Lat,Lon boxes.  There is, however, a routine
in McIDAS XRD (X Research and development) that can output the solar
zenith angle for individual points.  The routine I am referring to is

Since the XRD portion of the Unidata McIDAS-X distribution is not
built/installed by default, it is possible that you will have to build
and install it yourself:

<logged in as 'mcidas' on iset2>
cd ~/mcidas2009/src
make xrd
make install.xrd

Since XRD routines are not part of McIDAS core, their documentation can
be "sketchy", and they will not be found in the McIDAS-X User's Guide.
The only documentation for SATNAGLES is, therefore, through HELP:


The bad thing about SATANGLES is that it is usable for images that
are currently loaded into a McIDAS session frames.  One then has
to move the mouse cursor over a point and then run SATANGLES to
get information for the pixel selected.

The other MAJOR limit to using SATANGLES is that it only works
for select navigation types:

 SATANGLES -- Lists satellite zenith, solar zenith, and relative angles at 
cursor location
     Works for GOES, GVAR and GMS Navigation

     This is a renamed copy of a McIDAS-XRD 2007 routine called ANGLES.
     Renaming was needed since there is a subroutine in the McIDAS
     distribution called angles.for.

This means that it will work for your original images (e.g., images from
the G13/IR27APR11 dataset), but not for remapped images (e.g., images created

> Is there a way they can be in a ASCII text file?

SATANGLES does not have an option to write its output to ASCII text files,
but information for individual pixels can be written to ASCII text files
by specifying the DEV=T <fname> keyword sequence in SATANGLES invocations.

Since the solar zenith angle should not change drastically over the
area that you are interested in for a particular time, you may be
able to do spot checks to see if the pixels can be kept pursuant to
the guidelines you forwarded in a previous email:

> On Wed, Oct 31, 2012 at 11:01 AM, Dan Lindsey <address@hidden> wrote:
> Hi Nimrod,
> I calculate the solar zenith angle (it's a function of latitude,
> longitude, date, and time), and only consider effective radius
> retrievals valid when the solar zenith angle is less than 68 degrees
> (90 degrees means the sun is on the horizon, and 0 degrees means
> directly overhead). I don't know if MATLAB has a solar zenith angle
> routine.
> ...


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Ticket Details
Ticket ID: RDQ-637778
Department: Support McIDAS
Priority: Normal
Status: Closed

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