1. Quality Assurance Measures for High Frequency Radar Systems
Hugh Roarty , Ethan Handel, Erick Rivera,
Mike Smith, Colin Evans, John Kerfoot,
Josh Kohut ,Scott Glenn
Coastal Ocean Observation Laboratory
Institute of Marine & Coastal Sciences
Rutgers University
Quality Assurance Measures for High Frequency Radar Systems
ABSTRACT
MEASURED VS. IDEAL RADIALS
USE OF OPTIMAL INTERPOLATION
A High Frequency radar network is a major component of the Mid-Atlantic Regional Association Coastal Ocean Observing System (MARACOOS). This network has provided hourly surface current measurements to the US Coast Guard since In order to ensure that the data that is being sent to the Coast Guard for search and rescue is of the highest quality, a study of the radial vector generation and the combination of those radials into totals was conducted. The options available to the user were examined for their potential benefit. Initial findings indicate the use of measured antenna patterns gives improved results.
Kohut and Glenn (2003) and Paduan et al. (2006) have shown that the use of measured patterns improves results. The use of measured antenna patterns comes at an additional cost to the operator. We must understand the benefit of using measured antenna patterns to see if the cost is warranted. This will hold implications for the ~120 radars deployed around the country.
OI Settings
Sx 10 km
Model Variance
420 cm2/s2
U error <
0.6
Sy 10 km
Error Variance
66 cm2/s2
V error <
UWLS Settings
Spatial Threshold 10 km
GDOP <
1.25
+ toward
the radar
- Away from
Two outliers
Zero outliers
UWLS OI
Gulf of Maine
Coverage
26%
RMS U
15.9
15.2
RMS V
22.8
20.1
Mid Atlantic Bight
53%
65%
7.4
8.4
9.8
11.8
South Atlantic Bight
West Florida Shelf
50%
41%
11.7
11.5
13.4
12.9
Gulf of Mexico
49%
47%
14.0
13.7
11.1
USE OF THE ANGSEG.TXT FILE
Several options exist to the SeaSonde operator when measuring surface currents. Through the use of the AngSeg.txt file, radials over user defined sectors can be removed or radial velocities sent to the MUSIC direction finding algorithm can be forced over water. The potential benefit of these options is explored below.
Drifters from NOAA NEFSC
Spectra
Read In Spectra
Apply phases.txt to the ideal pattern , SeaSondeRadialSetup
Apply sea-echo amplitudes factors to the spectra, averaging the last 6hrs of amplitude calculations from the CSS
Pattern Method
Default
Water Only
Spectra analyzed using MUSIC algorithm
Radial File
AngSeg applied to Radial File
Filtered Radial File
AngSeg applied to pattern
RadialSlider
Apply amplitude correction factors for Loops 1 and 2,
Line 17 of header.txt, default value 1.0 and 1.0
The two boxes in yellow are skipped for the Measured pattern since the measured phases and amplitudes of the antenna are in the measured pattern.
Samples 1849
R 0.70
RMS Diff 13.7 cm/s
Y=0.62x-5.1
Samples 1483
R 0.70
RMS Diff 13.5 cm/s
Y=0.68x-3.7
Radial grid from the WILD HF Radar site overlaid with the location of the four moorings deployed as part of the 2007 Mid Shelf Front experiment. The data from these moorings was used as validation comparison against the settings changes on the HF radar.
T_Tide Analysis of the Ideal Radials, Measured Radials and the ADCP (4.4 m below the surface)
Gulf of Maine
Mid Atlantic Bight
WILD Radial Velocities and ADCP Comparison
Radial Shorts, Every 30 minutes, 1 degree
Major reason why operators don’t use measured radials, gaps in coverage
Case
Radial Type
Pattern Method
Corr
RMS Diff
Sample Size 11
Ideal
Water Only
0.77
24.7 cm/s 14
Meas
0.84
19.0 cm/s 15
Anywhere
0.78
25.0 cm/s 13
Water Only
Radials Anywhere
West Florida Shelf
Radial Shorts, Every 30 minutes, merged to 5 degree
Ideal Radial Coverage – 3 days
Measured Radial Coverage – 3 days
Case
Radial Type
Pattern Method
Corr
RMS Diff
Sample Size 11
Ideal
Water Only
0.44
27.5 cm/s 38
Meas
0.72
23.3 cm/s 37 14
Anywhere
0.51
26.7 cm/s 35
Case 9
Case 11
Case 12
Case 13
Case 14
Coverage Time
180 min
120 min
240 min
Output Interval
60 min
Doppler Interpolation
Did not exist
Off
Pattern Method
2 water only
0 Anywhere
AngSeg On
Type of Pattern
Measured 2006 (170° coverage)
Gulf of Mexico
S. Atl. Bight
RECOMMENDATIONS FOR NATIONAL NETWORK
Use measured antenna patterns when available
Develop a Best Practices Document for measuring and processing an antenna patterns