SARREPROJ

Description

SARREPROJ uses a digital elevation model (DEM) to project an orthorectified image into the viewing geometry of the SAR reference file. The viewing geometry of the reference SAR data set is determined from the orbital state vectors and look direction. The projection of the reference file (slant or ground range) and pixel spacing in azimuth and range is extracted from the metadata.

Parameters

Name	Type	Caption	Length	Value range
FILI *	String	Input Orthorectified file name	1 - 192
DBIC	Integer	Database reference input channels	0 -	1 -
DBVS	Integer	Database vector segment	0 -
FILREF *	String	SAR Reference file name	1 - 192
RESAMPLE	String	Resampling method	0 - 192
FILEDEM *	String	Input file name of digital elevation model	1 - 192
FILO *	String	Database output file name	1 - 192

* Required parameter

Parameter descriptions

FILI

The name of the orthorectified input file. The specified channels of the input file will be projected into the viewing geometry of the SAR reference file. If a DEM is specified as FILI, the elevations will be coregistered with the SAR reference file.

DBIC

The list of channel numbers from FILI to be re-projected. Ranges of channels can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

DBVS

The list of segments containing the geocoded polygons. The geocoded polygons will be reprojected to the viewing geometry of the reference file.

FILREF

The name of the SAR reference file. This file can be a detected or complex valued data set in either slant or ground range.

RESAMPLE

FILEDEM

The name of the input file containing the elevation data. The elevations are automatically resampled to match the sample size, earth model (usually WGS-84) and processing elevation of the SAR data set. If the DATUM metadata tag is not specified, mean sea level (MSL) in meters is assumed.

FILO

The name of the output file containing the re-projected channels. This file must not already exist. The output file will be written in the same projection (slant or ground range) and with the same number of image rows and columns as the SAR input file. Pixels which do not overlap with the DEM are marked as NO DATA.

Details

The user specified DEM is projected and resampled to match the viewing geometry and sample sizes of the reference file. The re-projected elevation is used to determine the shift to be applied to each pixel from the orthorectified file. Areas not covered by the DEM will be marked as NO DATA. Geocoded polygons such as water boundaries or road networks can also be reprojected to align with the reference SAR data set.

Examples

In the following example, we will re-project four channels of an optical Landsat image and a network of geocoded vectors stored in segment 3 into the slant range viewing geometry of the reference SAR data set. The DEM file is automatically converted from MSL to WGS-84. The output file will have the same number of image rows and columns as the reference file and will contain the number of channels specified by the DBIC parameter.

EASI>FILI = "Landsat_8.pix"                ! Landsat data as input
EASI>DBIC = 1,2,3,4                        ! re-project first 4 channels
EASI>DBVS = 3                              ! segment containing vector network
EASI>FILREF = "RSAT2_slant_range.pix"      ! SAR reference data set
EASI>FILEDEM = "N38W123.hgt"               ! digital elevation model
EASI>FILO = "Slant_range_Landsat_8.pix"    ! name of output file
run SARREPROJ
    

In the next example, we will re-project a DEM into the ground range viewing geometry of the reference SAR data set.

EASI>FILI = "N38W123.hgt"                  ! digital elevation model
EASI>DBIC =                                ! default channel
EASI>DBVS =                                ! no vector info to add
EASI>FILREF = "RSAT2_ground_range.pix"     ! SAR reference file
EASI>FILEDEM = FILI                        ! DEM is the input file
EASI>FILO = "Ground_range_DEM.pix"         ! name of output file
run SARREPROJ