Gamma ISP: Reference Manual

DELFT_vec2

ANSI-C program: DELFT_vec2.c

<SLC_par>	SLC image parameter file
<DELFT_dir>	directory containing Delft orbit arclist and ODR files for ERS-1, ERS-2 or ENVISAT) NOTE: enter . to specify the current directory
[nstate]	number of state vectors to generate (enter - for default (>= 15)
[interval]	time interval between state vectors in the ISP image parameter file (s) (default: 10.0)
[ODR]	ODR file to use (include path) rather than ODR file determined from the Delft orbit arclist

EXAMPLE
DELFT_vec2 199960421.slc.par /raid/Delft/ers1/eigen_gl04s

DESCRIPTION
DELFT_vec2 uses ERS-1, ERS-2, and ENVISAT position state vectors available by the Technical University of Delft to generate position and velocity state vectors for use by the MSP. Details on the Delft orbit data are available at the web site http://www.deos.tudelft.nl/ers/precorbs. The orbit position data from Delft is provided as binary Orbital Data Record (ODR) files along with an arclist text file specifying the start and stop times for each of the ODR files. Recently these state vectors have been recomputed and the improved orbit data are available from http://www.deos.tudelft.nl/AS/pieter/Local/ERS/index.html.

The ISP image state vectors include both the position and velocity. Since the ODR data provide only the platform position, DELFT_vec2 calculates the velocity vector for each state vector in the ODR file. DELFT_vec2 calculates the number of state vectors required to cover the scene with sufficient overlap of the scene start and end.. The default number of state vectors is 7, though any value up to 64 can be specifiied on the command line.

The time interval between the ODR state vectors is 60 sec. DELFT_vec2 resamples the state vector data to evenly spaced set of vectors (default 10.0 sec interval) and writes the interpolated state vectors into the ISP image parameter file. The default time interval value should be at least 5 sec. Furthermore there should be several state vectors both before and after the data interval to obtain the most accurate interpolation in the ISP and DIFF/GEO processing.

Each ODR data have best accuracy after a time specified in the ODR header that is some hours after the time of the first state vector in the ODR file. In cases where no ODR file is available with the data at the highest accuracy, the user can specify a specific ODR file to use on the command line. DELFT_vec2 checks to see if the ODR file covers the time period of the SAR imge file.