20020415: calculating areas using McIdas

Mick,

I believe that Jeff is referring to the McIDAS command ASTAT. As far as
I can tell, ASTAT is not part of the core McIDAS application set, but
it does reside in XRD and there is also a copy in the McIDAS developers
Forum.  ASTAT allows the user to draw an outline around a "target"
using the graphics.  Once the outline is complete, the application will
compute basic statistics (mean, mode, max, min,. ..)  for the pixels
contained within the outline. The current version does not compute
earth area and does not account for a parallax shift.

You will find a copy of the help listed below.

Russ Dengel


C ? ASTAT -- Measure image statistics
C ?    ASTAT opt coord <keywords>
C ?
C ? Parameters:
C ?    opt - option type
C ?          BOX | rectangular outline (default)
C ?          CIR | circular or ellipitical outline
C ?          IRR | irregular shaped outline
C ?          LIN | outline based on line between 2 points
C ?    coord - coordinate type
C ?          IC | image coordinates (default)
C ?               All options are designed to run interactivly on the
C ?               current image frame.
C ?          EC | earth coordinates
C ?               CIR EC STA=stn1 RAD=rad - STATION loc and radius
C ?               CIR EC LAT=lat1 lon1 RAD=rad - LatLon pair and radius
C ?               BOX EC LAT=lat1 lon2 lat2 lon2 - LATLON pairs
C ?               LIN EC STA=stn1 stn2 WID=wide  - STATION locs and width
C ?               LIN EC LAT=lat1 lon1 lat2 lon2 WID=wide - LATLON pairs and 
width
C ?
C ? Keywords:
C ?    ARC=barc earc | angular segment of an circle (def=0 360)
C ?    BANd=band | spectral band (def=current)
C ?    COLor=color | outline graphics color (def=2)
C ?    CUT=limit threshold | restrict the data range within the specified limit

C ?                          and threshold; limit and threshold are exclusive;
C ?                          (def limit=-99999.0 threshold=99999.0)
C ?    GRAphic=frame | outline graphics frame (def=current)
C ?    HISt=color frame | histogram color and graphic frame (def=0 current)
C ?    LATlon=lat lon ... latN lonN | latitude longitude pair(s)
C ?    MODe = mode | command mode I=interactive, B=batch (def=I)
C ?    RADius= | CIRCLE radius (def=50KM)
C ?    RANge=rng1...rngN | breakpoint statistics (def=no breakpoints)
C ?    SCAle=factor | external scaling factor applied to data elements (def=1.0)
C ?    STAtion=stn1 ... stnN | station id(s)
C ?    SU=name | name of stretch table to apply to data (def=no table)
C ?    TAIl=pct | tail percentage 0-100 (def=5%)
C ?    UNIt=unit | calibration units (def=BRIT)
C ?    WIDe= | LINE (corridor) width (def=10KM each side of the LINE)
C ?
C ? Remarks
C ?    Use CUT to specify a precise range of data values to include when
C ?    calculating the statistical values. The stated limit and threshold
C ?    mark the EXCLUDED boundaries of the dataset. Values equal to or below
C ?    the limit are not included and values at or above the threshold are
C ?    not included. If no pixels fall within the data range, the stated
C ?    values of all statisics will be 0.
C ?
C ?    Use RANGE to specify breakpoints within the dynamic range of the sample.
C ?       FORMAT: RANGE= beg-endBinc
C ?               where  beg - beginning data value (def=none)
C ?                      end - ending data value (def=beg)
C ?                      inc - breakpoint increment (def=end)
C ?       EXAMPLE: RANGE=0-255B10 UNIT=BRIT
C ?                Generates statistics for the pixels in the sample
C ?                corresponding to breakpoints at every 10 brightness
C ?                counts (0-9, 10-19, ... 250-255).
C ?       EXAMPLE: RANGE=0-30 100 200-255 UNIT=BRIT
C ?                Generates statistics for the pixels in the sample
C ?                corresponding to the breakpoints 0<->30, 100<->100,
C ?                and 200<->250.
C ?
C ?    Note that CUT values determine the overall limits of the data used to
C ?    compute sample statistics, while the RANGE values mark breakpoints within
C ?    these limits. RANGE breakpoints are INCLUSIVE as opposed to CUT values
C ?    which are EXCLUSIVE.
C ? ----------

Mick Pope wrote:

> G'day group,
>
> another newbie question about sat imagery.
>
> I am doing some research into convection and am interested in the lifecycle
> of the convection.  I've already been enjoying the pleasures of stretch
> tables, EU and BAR, and now have something that looks good and is vaguely
> useful for working out min CTTs.
>
> But, I want to know the total cloud area below a certain threshold
> temperature.  Is there a way of calculating the number of pixels &/or the
> actual area in km^2 for this?
>
> Jeff Wilson, my local guru suggested there was a command that could do this?
> Any thoughts?  If not, does anyone have experience in writing code to do
> this?
>
> Cheers!
>
>  Mick Pope                                        / / / / / / / / /
> "Elucidator of Meteorological Phenomena"         / / ______/ / / /
>  Bureau of Meteorology Training Centre (BMTC)   / / /   |  \  / /
>  Bureau of Meteorology, GPO Box 1289K          / /  (__)|    / /
>  Melbourne, Vic, Australia 3001.              / /   (oo)|   / /
>  (03) 9669 4109, address@hidden           /-------\/ |  / /
>                                             / |     ||^_|
>                                            *  ||----|
>                                               ^^    ^