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6.6.8 Doppler Centroid parameters
The Doppler centroid 2.6.1.2.2. of the
image is estimated once for stand-alone products , and
is hence reported once. For stripline , however, a Doppler
centroid estimate is performed at least at the
start and at the end of a slice . To ensure the user is
given a
complete record of the Doppler
parameters used during processing, the Doppler
Centroid Coefficients ADS is updated with a new ADSR
at every granule for stripline
processing. Each update is time stamped with the
zero Doppler time to
which the update applies. The Doppler centroid
coefficients used on range lines between two
updates are found by linear interpolation
between the updated and previous values. The
contents of each update (each update is a
single ADSR within the ADS) are as shown in the
table below:
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Table 6.44 Doppler Centroid parameters
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Doppler Centroid parameters
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#
|
Description
|
Units
|
Count
|
Type
|
Size
|
|
Data Record
|
|
0
|
zero_doppler_time
Zero Doppler
azimuth time at which estimate applies |
MJD |
1 |
mjd |
12 byte(s) |
|
1
|
attach_flag
Attachment Flag
Always set to zero for
this ADSR
|
flag |
1 |
BooleanFlag |
1 byte(s) |
|
2
|
slant_range_time
2-way slant range
time origin (t0) |
ns |
1 |
fl |
4 byte(s) |
|
3
|
dop_coef
Doppler centroid
coefficients as a function of
slant range time: D0, D1, D2,
D3, and D4. Where
Doppler Centroid = D0 +
D1(tSR-t0) + D2(tSR-t0)2 +
D3(tSR-t0)3 + D4(tSR-t0)4
|
HzHz/sHz/s2Hz/s3Hz/s4 |
5 |
fl |
5*4 byte(s) |
|
4
|
dop_conf
Doppler Centroid
Confidence Measure.
Value between 0 and 1, 0
= poorest confidence, 1=
highest confidence
|
- |
1 |
fl |
4 byte(s) |
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5
|
dop_conf_below_thresh_flag
Doppler Centroid
Confidence below threshold flag.
0=confidence above
threshold, centroid
calculated from data;
1=confidence below
threshold, centroid
calculated from orbit parameters
|
flag |
1 |
BooleanFlag |
1 byte(s) |
|
6
|
delta_dopp_coeff
Delta Doppler
coefficents DelatD0(SS1) ,
DelatD0(SS2) DelatD0(SS3)
DelatD0(SS4) DelatD0(SS5) |
- |
5 |
ss |
5*2 byte(s) |
|
7
|
spare_1
Spare |
- |
1 |
SpareField |
3 byte(s) |
DS_NAME : Doppler Centroid parameters
Format Version 114.0
Note: For Field# 5:
Doppler Centroid Confidence Measure:
Value between 0 and 1, 0 = poorest confidence, 1=
highest confidence
If multiple Doppler Centroid estimates were
performed, this value is the lowest confidence
value attained.
Doppler
Confidence Below Threshold Flag
0 = confidence above threshold, Doppler Centroid
calculated from data
1 = confidence below threshold, Doppler Centroid
calculated from orbit parameters
For a discussion of the Doppler Centroid
estimation algorithms, refer to the included
technote " Doppler Centroid
Frequency Estimator " . 2.6.1.2.2. See also " Level 1B Essential
Product Confidence Data " 2.6.2.3. in
chapter 2.
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Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,
atmospheric chemistry
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