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ASA_WS__BP: ASAR Wide Swath Browse Image
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ASA_WV__0P: ASAR Wave Mode Level 0
ASA_WS__0P: ASAR Wide Swath Mode Level 0
ASA_MS__0P: ASAR Level 0 Module Stepping Mode
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ASA_GM__0P: ASAR Global Monitoring Mode Level 0
ASA_EC__0P: ASAR Level 0 External Characterization
ASA_APV_0P: ASAR Alternating Polarization Level 0 (Cross polar V)
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ASA_IMS_1P: ASAR Image Mode Single Look Complex
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ASA_WVS_1P: ASAR Wave Mode Imagette Cross Spectra
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6.6.9 Geolocation Grid ADSRs

The Geolocation Grid is a table which lists the slant range time, incidence angle, and geodetic latitude and longitude positions at various range/azimuth positions within the image. The location of each tie point (or grid point) in the image is specified by
a line and sample co-ordinate system. Tie point locations in azimuth are specified using the Zero Doppler Time stamp found at the start of each range line in the MDS. The location in range is specified by the number of range samples. Tie points must
be placed at points corresponding to an integer number of range samples, and tie points must be located at least the following 3 points within those reported: the first range sample of the range line, the mid swath range sample, and the last range
sample of the range line.

For Geocoded products, the Zero Doppler Time stamp does not apply. Therefore, it is set to zero, and only the range line number is used to index the grid entries.

The grid spacing in azimuth defines the granule size of the ASAR product. That is, a grid line provides tie points for the first line and last line of a granule. There will be 11 grid updates in range per ADSR. In azimuth, a new ADSR will be added to the ADS nominally every:
  • 10 km in azimuth for IM and AP;
  • 40 km in azimuth for WS and GM.
The contents of a Geolocation Grid ADSR are shown below:
Table 6.45 Geolocation Grid ADSRs

Geolocation Grid ADSRs

# Description Units Count Type Size
Data Record
0 first_zero_doppler_time
Zero doppler time in azimuth of first line of the granule

Gives azimuth location of grid line for first line of the granule.

MJD 1 mjd 12 byte(s)
1 attach_flag
Attachment Flag

Set to 1 if all MDSRs corresponding to this ADSR are blank, set to zero otherwise

flag 1 BooleanFlag 1 byte(s)
2 line_num
Range line number corresponding to the first line of the granule within the slice.

Warning: (1) This is not always the record number of the corresponding image MDSR. Use the number of lines per granule field to determine the image MDS record corresponding to each record of tie points.(2) For a stripline product, which may consist of multiple slices in a single MDS, this number is reset to 1 at the beginning of each slice.(3) For child products, which are subsets of a full product, the range line number in the first record may not be 1.

- 1 ul 4 byte(s)
3 num_lines
Number of output lines in this granule
lines 1 ul 4 byte(s)
4 sub_sat_track
Subsatellite track heading (relative to North) for first line of granule

This is the heading on the ground (includes Earth rotation)

deg. 1 fl 4 byte(s)
5 first_line_tie_points
First Line Tie Points

The following fields each contain 11 values corresponding to 11 tie points in the first line of the granule

- 1 first_line_tie_pointsStruct 220.0 byte(s)
a samp_numbers
Range sample number Gives the range location of the grid points. First range sample is 1, last is M
- 11 ul 11*4 byte(s)
b slant_range_times
2 way slant range time to range sample
ns 11 fl 11*4 byte(s)
c angles
Incidence Angle at range sample
deg. 11 fl 11*4 byte(s)
d lats
geodetic latitude (positive north)
(1e-6) degrees 11 GeoCoordinate 11*4 byte(s)
e longs
geodetic longitude (positive east)
(1e-6) degrees 11 GeoCoordinate 11*4 byte(s)
6 spare_1
Spare
- 1 SpareField 22 byte(s)
7 last_zero_doppler_time
Zero doppler time for the last line of the granule
MJD 1 mjd 12 byte(s)
8 last_line_tie_points
Last Line Tie Points

The following fields each contain 11 values corresponding to 11 tie points in the last line of the granule

- 1 last_line_tie_pointsStruct 220.0 byte(s)
a samp_numbers
Range sample number Gives the range location of the grid points. First range sample is 1, last is M
- 11 ul 11*4 byte(s)
b slant_range_times
2 way slant range time to range sample
ns 11 fl 11*4 byte(s)
c angles
Incidence Angle at range sample
deg. 11 fl 11*4 byte(s)
d lats
geodetic latitude (positive north)
(1e-6) degrees 11 GeoCoordinate 11*4 byte(s)
e longs
geodetic longitude (positive east)
(1e-6) degrees 11 GeoCoordinate 11*4 byte(s)
9 spare_2
Spare
- 1 SpareField 22 byte(s)
Record Length : 521

DS_NAME : Geolocation Grid ADSRs



Format Version 114.0