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National Aeronautics and Space Administration

Goddard Space Flight Center

ALT

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Data Products

Data Products

Level 1: Waveform Data Record (WDR)

Level 1 data available via the on-line data base is orbital format waveform data records at the full data rate (10/sec for Seasat and Geosat, and 20/sec for ERS and ENVISAT) which contain the time, location altimeter return waveform, and retracking parameters.

Binary Direct Access WDR file description (184 bytes)

WDR Header Record:

BYTES TYPE DESCRIPTION
1-2 C*2 "WH" for WDR header
3-16 C*14 Name of rev access directory to use to read this file
17-30 C*14 Name of georeference directory that corresponds to this file
31-44 C*14 Name of bin/rev directory that corresponds to this file.
45-48 I*4 Version No. of this data base - same as used in name
49-52 I*4 Year month day of beg of file YYMMDD
53-56 I*4 HHMMSS OF BEGINNING OF FILE
57-60 I*4 YYMMDD OF END OF FILE
61-64 I*4 HHMMSS OF END OF FILE
65-68 I*4 SATELLITE ID
69-76 C*8 CONTINENT OR OCEAN COVERED BY DATA BASE
77-184 ??? Spares

WDR Processing Record:

Bytes Type Description
1-2 C*2 "WP" for WDR processing record
3-8 C*6 YYMMDD - year, month, day of date processed
8-26 C*18 Name and version number of processing program (i.e. BINS8902)
27-40 C*14 Name of input file # 1
41-184 ??? Names of other input files in C*14 variables

WDR Database Configuration Record:

Bytes Type Description
1-4 C*4 "WC " - for WDR data base configuration
5-8 I*4 latitude in .01 deg N of beg of data base
9-12 I*4 latitude in .01 deg N of end of data base
13-16 I*4 longitude in .01 deg E of beg of data base
17-20 I*4 longitude in .01 deg E of end of data base
21-184 ??? Spares

WDR Row Descriptor Record:

Bytes Type Description
1-4 C*4 "WS " - for WDR Row descriptor record giving latitude and longitude division sizes that pertain to these rows
5-8 I*4 beg row number that information on this rec pertains to where row 1 corresponds to beg latitude
9-12 I*4 end row number that information on this rec pertains to where row 1 corresponds to beg latitude
13-16 I*4 size of latitude division between individual rows. This pertains to the beg row through the end row -1 in .01 deg
17-20 I*4 number of longitude divisions in each row
21-184 ??? Spares

There can be as many header records as required as long as they start with the letter "C" and are placed in the header region of this file. The order of the header records is not important as long as they all precede the data records.

WDR Rev Record:

Bytes Type Description
1-4 C*4 "WR " for WDR Rev
5-8 I*4 Rev number
9-12 I*4 Date of first processed data rec in pass begin (MJD)
13-16 I*4 Time of first processed data rec in pass (sec)
17-20 I*4 Fractional seconds of time of first processed data rec in pass (microsec)
21-24 I*4 Longitude of asc node ( microdeg)
25-184 ??? Spares

WDR Data Record:

BYTES TYPE DESCRIPTION
1-2 C*2 File/Record type "WD" for WDR data
3-4 I*2 Retracking status word part 1
5-8 I*4 Time in microsec from time on pass header record
9-12 I*4 Latitude in microdeg N
13-16 I*4 Longitude in microdeg E
17-20 I*4 Surface Height relative to the ellipsoid - original orbit (cm)
21-24 I*4 Surface Height status word

Bytes 25-42 contain the parameters describing the function used to fit the waveform for GSFC retracking.

25-26 I*2 þ(1) = Noise level in 0.1 counts
27-28 I*2 þ(2) = Amplitude increment to top of erf for first ramp in counts
29-30 I*2 þ(3) = Gate of midpoint of erf for first ramp in .01 gates
31-32 I*2 þ(4) = Rise time of erf for first ramp in 0.1 gates
33-34 I*2 þ(5) = Amplitude increment to top of erf for second ramp in counts
35-36 I*2 þ(6) = Gate of midpoint of erf for second ramp in .01 gates
37-38 I*2 þ(7) = Rise time of erf for second ramp in 0.1 gates
39-40 I*2 þ(8) = Exponential decay factor for second ramp in (.0001/Gates)
41-42 I*2 þ(9) = slope between first and second ramps in (.01/gate)
43-44 I*2 Waveform Peakiness (x1000)
45-46 I*2 Tracking gate (.01 gates)
47-48 I*2 AGC in .01 dB
49-50 I*2 H13 in cm
51-178 I*2 Waveform 64 Gates in counts
179-180 I*2 Sigma Naught in .01 dB !! Corrected 4/26/2001 by JPD
181-182 I*2 Retracking status word part 2
183-184 I*2 spares