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.