IMGGRD
Analyzes satellite image data onto a grid
Format
IMGGRD <Keywords> "text
Parameters
- "text
- identifying label in grid directory (no default)
Keywords:
- AREA=
- area number (default=current frame)
- BAND=
- band/channel number (default=current frame)
- ELE=e1 e2, pixel element range to be analyzed (default=cursor or
if AREA keyword specified then default=area domain)
- FORM=
- output format SUM,AVG,STD, in any combination or sequence
(default=AVG)
- GRIDF=
- gridfile number (default=current)
- GRID=
- grid number (default=0)
- INC =
- inclat inclon, grid increments in deg (default=1.0 inclat)
- LAT=se nw, latitude values for the SE and NW psudeo-mercator grid
corners (default=-89.0 +89.0)
- LIN=l1 l2, pixel line range to be analyzed (default=cursor or
if AREA keyword specified then default=area domain)
- LON=se nw, longitude values for the SE and NW psudeo-mercator grid
corners (default=-180.0 +180.0)
- FACTOR= internal scaling factor of calibration type (default=1.0)
- UNIT=
- output calibration type| BRIT,TEMP,RAD,RAW (default=BRIT)
- ZERO=
- zero pixel value option as MISSing or as DATA, or can
indicate a specific non-zero integer as the missing value
code (default=MISS)
Remarks
Maximum grid size is 65K. McIDAS grid Type=4.
Latitude/Longitude values can be entered in DDD.xxx or DDD:MM:SS
format
- Grid points off the image area are assigned a missing value code
For large areas the program is fairly time consuming. This can be alleviated
to some extent by using the REMAP command to reduce the image
resolution (e.g. reducing a 4km image to a 16km image will not drastically alter
the results for a 1x1 degree gridding, but will reduce the cpu time by a factor
of 16).
- It has also been found that images stored in a MERC projection
are manipulated much faster by the program because the transform from image
lat/lon to grid lat/lon is much faster.
-
-
- Can use multiple IMGGRD calls to cover a large image area
with a higher resolution gridding increment.
-
Zero pixel values can be treated as a missing value code or as real data value.
The option also exists to user specify a different pixel value to use as a missing
value code.
- Bi-linear interpolation is used to calculate the corresponding Lat/Lon
location for each pixel, except near the poles where each pixel is individually
navigated.The interpolation corner points are updated at every Lat/Lon grid
increment. The use of this type of scheme also helps to improve the program's
performance.
-
-
- Note that for GOES imagery temperatures are stored as 4-digit
values, and therefore a FACTOR=10.0 must be used in order
for them to be properly interpolated.
-
-
- If attempting to grid a satellite image which includes a pole, then it
is necessary to use the LIN/ELE keywords
to set the pixel line and element ranges to be analyzed, because an ambiguity
exists with the calculation of the default values due to the polar singularity.
