Gamma MSP: Reference Manual

multi_GRD_SLC

NAME
multi_GRD_SLC - Generates multi-look ground range intensity images from complex SAR SLC data.

SYNOPSIS
multi_GRD_SLC <SLC_PROC_par> <GRD_PROC_par> <SLC_image> <GRD_image> [rlks] [azlks] [interp_mode] [samp_spacing] [t_start] [t_end]

<SLC PROC_par>	(input) MSP SLC processing parameter file
<MLI PROC_par>	(output) MSP ground range (GRD) multi-look image parameter file
<SLC_image>	(input) SLC image file
<GRD_image>	(output) ground range projected image file
[rlks]	number of range looks (default=1)
[azlks]	number of azimuth looks (default=1)
[interp_mode]	interpolation mode 0:nearest neighbor 1=SINC (default)
[samp_spacing]	multilook image sample spacing (m) (default = azimuth SLC spacing * azlks)
[gr_start]	starting ground range (meters) (enter - for default: start of data)
[t_start]	starting time (s) for output, (default - : start of data)
[t_end]	ending time (s) for output, (default: end of data)

EXAMPLE
multi_GRD_SLC p8560.slc.par p8560.grd.par 8560.slc 8560.grd 1 3 12.5

Generates ground range multi-look images products. It can be used to generate multi-look detected images that are similar to the ESA PRI product for ERS data.

DESCRIPTION
This program resamples the SLC image into ground range geometry, detects the these data to make a multi-look image. The detected intensity image is stored as 4-byte floating point numbers. The program uses either nearest-neighbor or SINC interpolation to resample the output image into the desired sample spacing. The ground range is determined by making a best spherical fit to the earth curvature across track, perpendicular to the heading. The distance from the satellite ground track to the start of the image swath in ground range is stored in the range to start of image parameter in the p*.grd.par file.

The number of looks selected in range and azimuth should roughly correspond to the desired image spacing to achieve the best radiometric and geometric fidelity. If the output image spacing is not specified, then the azimuth spacing, determined by multiplying the SLC azimuth spacing by the number of azimuth looks, is selected for the ground range spacing. In order to emulate the PRI product from ESA for the ERS AMI instrument, the number of range looks is 1, azimuth looks is 3, and the pixel spacing is specified to be 12.5 meters. The output image parameters image size, pixel spacing [m], number of looks are written to new processing parameter file.

The default two-dimensional SINC interpolation is gemetrically and radiometrically more accurate than the nearest neighbor interpolation algorithm. Either method permits independent selection of the output spacing and the number of looks in range and azimuth.

The user can also specify the starting time and nominal ending time of the image on the command line. The true ending time of the data is an integer number of time intervals between lines. The time interval between output lines dt is determined by the azimuth line spacing in the output az_grd, the pulse repetition interval prf, and the azimuth spacing between lines in the SLC image az_slc.

dt = az_grd * az_slc / prf

SLC input image data may be displayed using disSLC, the (real) output multi-look image using dispwr. Alternately, the intensity image can be scaled and stored as a SUN raster or BMP format image using raspwr or ras_linear.