Gamma DIFF&GEO: Reference Manual

look_vector

NAME
look_vector - Calculation of SAR look-vector direction (pointing towards SAR) in map geometry.

SYNOPSIS
look_vector <SLC_par> <OFF_par> <DEM/MAP_par> <DEM> <lv_theta> <lv_phi>

<SLC_par>	(input) parameter file of SLC
<OFF_par>	(input) ISP offset/interferogram parameter file enter - for SLC or MLI data
<DEM/MAP_par>	(input) DEM/MAP parameter file
<DEM>	(input) DEM data file (or constant height value)
<lv_theta>	(output) SAR look-vector elevation angle (at each map pixel) lv_theta: PI/2 -> up, -PI/2 -> down
<lv_phi>	(output) SAR look-vector orientation angle at each map pixel lv_phi: 0 -> East, PI/2 -> North

EXAMPLE
look_vector 8560.slc.par 8560_9562.off aoi.dem_par aoi.dem aoi.lv_theta aoi.lv_phi

Calculates the look vector elevation (theta) and orientation (phi) angle fields (in map geometry).

look_vector 8560.rmli.par - aoi.dem_par aoi.dem aoi.lv_theta aoi.lv_phi

Calculates the look vector elevation (theta) and orientation (phi) angle fields (in map geometry).

INSTALLATION
Source code look_vector.c in ./src. For compilation adjust and use Makefile: Executable version look_vector in ../bin

AVAILABILITY
Uses ISP and DIFF type definition files typedef_ISP.h, typedef_DIFF.h.

DESCRIPTION
look_vector calculates SAR look-vector direction (pointing towards SAR) in map geometry.

Based on the SAR imaging and DEM geometries the look vector is calculated for each pixel of the DEM/map section specified in the DEM parameter file. The local topography is taken into account. The look vector is expressed in the local map coordinates through the SAR look-vector elevation angle and the SAR look-vector orientation angle, both calculated at each map pixel.

The SAR image geometry is specified in the SLC/MLI and ISP offset/interferogram parameter files for (multi-looked) interferometric datasets or in the SLC/MLI parameter file for SLC or MLI data.

The map projection is defined in the DEM/map prameter file.

The output look vector elevation and orientation angles are stored in separate binary files (float). The look vector elevation angle is defined as the angle between the horizontal surface and the look vector with positive angles indicating sensor positions above the surface. The look vector orientation angle is defined as the angle between the East direction and the projection of the look vector on the horizontal surface plan. The orientation angle increases towards north, with the North direction corresponding to PI/2 (and south to -PI/2). Both angles are expresed in radian.

An important use of look vectors expressed in map geometry is the interpretation of surface deformation - the DINSAR approach provides the deformation component in the look vector direction.

The look vector information as provided by the program look_vector is used in the calculation of 3D look vector fields from differential interferometric observations and an deformation direction field as supported by the programs dispmap_vec and dispmap_vec2.

OPTIONS
None.