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6.6.14 Ocean Wave Spectra
This MDS contains the ocean wave spectrum of
the imagette . There is one MDSR
per wave cell. The format of the
wave-spectrum MDS closely matches that of the cross spectrum MDS where
some fields in the cross-spectrum MDS are
substituted
by new values pertaining
to the ocean wave spectrum product. Each ocean
wave spectrum MDSR is described below:
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Table 6.51 Ocean Wave Spectra
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#
|
Description
|
Units
|
Count
|
Type
|
Size
|
|
Data Record
|
|
0
|
zero_doppler_time
First Zero Doppler
Azimuth time of the wave cell.
Time of first range line in the
SLC Imagette MDS described by
this data set |
MJD |
1 |
mjd |
12 byte(s) |
|
1
|
quality_flag
Quality
Indicator. (-1 for
blank MDSR, 0 otherwise)
|
flag |
1 |
BooleanFlag |
1 byte(s) |
|
2
|
range_spectral_res
Range spectral bin
size of the cartesian cross spectrum |
- |
1 |
fl |
4 byte(s) |
|
3
|
az_spectral_res
Azimuth spectral
bin size of the cartesian cross spectrum |
- |
1 |
fl |
4 byte(s) |
|
4
|
spare_1
Spare |
- |
1 |
SpareField |
4 byte(s) |
|
5
|
spec_tot_energy
Spectrum Total Energy |
- |
1 |
fl |
4 byte(s) |
|
6
|
spec_max_energy
Spectrum Max Energy |
- |
1 |
fl |
4 byte(s) |
|
7
|
spec_max_dir
Direction of
Spectrum Max (deg)
Direction is given
clockwise from north in the
direction the wave propogates
|
deg |
1 |
fl |
4 byte(s) |
|
8
|
spec_max_wl
Wavelength of
Spectrum Max (m)
On higher resolution grid.
|
m |
1 |
fl |
4 byte(s) |
|
9
|
az_image_shift_var
Variance of the
azimuth image shift caused by
the orbital velocity |
m^2 |
1 |
fl |
4 byte(s) |
|
10
|
az_cutoff
Azimuthal Clutter
Cut-off wavelength (m) |
m |
1 |
fl |
4 byte(s) |
|
11
|
nonlinear_spectral_width
Spectral width of
the non-linear part of the cross spectra |
m |
1 |
fl |
4 byte(s) |
|
12
|
image_intensity
Image Intensity |
- |
1 |
fl |
4 byte(s) |
|
13
|
image_variance
Normalised image variance |
- |
1 |
fl |
4 byte(s) |
|
14
|
spare_2
Spare |
- |
1 |
SpareField |
56 byte(s) |
|
15
|
min_spectrum
Min value of ocean
wave spectrum |
m^4 |
1 |
fl |
4 byte(s) |
|
16
|
max_spectrum
Max value of ocean
wave spectrum |
m^4 |
1 |
fl |
4 byte(s) |
|
17
|
spare_3
Spare |
- |
1 |
SpareField |
8 byte(s) |
|
18
|
wind_speed
Wind speed used in
the wave spectra retrieval (m/s) |
m/s |
1 |
fl |
4 byte(s) |
|
19
|
wind_direction
Wind direction
used in the wave spectra
retrieval.
(clockwise from north
from where the wind from if
confidence is 0, relative to
range otherwise) (deg)
|
deg |
1 |
fl |
4 byte(s) |
|
20
|
norm_inv_wave_age
Normalised inverse
wave age |
- |
1 |
fl |
4 byte(s) |
|
21
|
SAR_wave_height
SAR swell wave height |
m |
1 |
fl |
4 byte(s) |
|
22
|
SAR_az_shift_var
Variance of the
azimuth shift computed from the
SAR swell wave spectra |
m^2 |
1 |
fl |
4 byte(s) |
|
23
|
backscatter
Radar backscatter
cross section |
dB |
1 |
fl |
4 byte(s) |
|
24
|
confidence_swell
Confidence measure
of the swell inversion. 0 =
inversion successful (a unique
spectrum in terms of propagation
direction); 1 =
inversion not successful
(symmetric spectrum) |
- |
1 |
us |
2 byte(s) |
|
25
|
signal_to_noise
Average
signal-to-noise ratio |
- |
1 |
fl |
4 byte(s) |
|
26
|
radar_vel_corr
Radar velocity
off-set correction |
m/s |
1 |
fl |
4 byte(s) |
|
27
|
cmod_cal_const
Geophysical
Calibration constant - CMOD |
- |
1 |
fl |
4 byte(s) |
|
28
|
confidence_wind
Confidence measure
of the wind retrieval. 0 =
external wind direction used
during inversion; 1 = external
wind direction not used
during inversion. |
- |
1 |
us |
2 byte(s) |
|
29
|
spare_4
Spare |
- |
1 |
SpareField |
24 byte(s) |
|
30
|
ocean_spectra
Ocean Wave Swell
spectra polar grid.
Number of bins in
wavelength and direction
defined in SPH (nominally 24
by 36). Arranged as 24
wavelength cells from
longest to
shortest wavelength, for
zero degrees, then 10
degrees, up to 350 degrees
(i.e clockwise direction).
|
- |
|
uc |
1 byte(s) |
DS_NAME : Ocean Wave Spectra
Format Version 114.0
The ocean wave spectrum is given in the MDS as real samples
distributed on a polar grid. The size of the
ocean wave spectrum grid is given in the SPH . Typically this will
be 24 by 36 bins in wavelength and direction respectively.
The ocean wave spectrum values shall be stored in
an unsigned integer format, each part linearly
scaled to the maximum and minimum values of
the representation (e.g., 0 to 255). The
original maximum and minimum values are reported.
The detected spectrum statistics are derived from
a high-resolution polar spectrum, prior to
encoding for output to the product, or at
other intermediate stages of the processing.
If the processor is unable to produce the ocean
wave spectra for a given wave cell, the MDSR is
time stamped with the time that the ocean
wave spectra would have corresponded to, the Quality Flag is set to
-1, and the MDSR data fields are all set
to zero.
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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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