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Radar stage sensors and other instrumentation issues
from the ICOM (Instrumentation Committee)
November 14, 2006
James Fallon
Annual COE-NWS-USGS Mississippi Valley meeting
Memphis, Tennessee
13-04-2006
Radar stage sensor information Radar stage sensor information adapted* from: adapted* from:
USGS Hydrologic Instrumentation USGS Hydrologic Instrumentation FacilityFacility
Testing Section Project UpdatesTesting Section Project Updates
ICOM meetingICOM meetingJuly 11, 2006July 11, 2006
*(Brand) names have been changed to protect against endorsements
• Instrumentation Development
• Commerically Available Instrumenation (ICOM)
• Radar Stage Measurement (ICOM)
HIF Testing ProjectsHIF Testing Projects
Timeline of radar stage sensors• 1999: Radar stage sensors tested at
the HIF, tracked by ICOM. Issues:– Accuracy, range, FCC licensing,
temperature effects, communication, power conversion, wave and rain interference
• 2002: Most technical issues seemed OK, HIF stocks unit, ICOM ends project, asks for more field, product testing
• 2003: New issues emerge:– Reports indicate accuracy of instrument
dependent upon water conditions (roughness, wave height and frequency).
– New generation of products need testing.
– Does current definition of stage accuracy apply to new method?
– What are installation requirements?Apollo rocket inspection building near the HIFused for static tests of radars in early testing
USGS stage-accuracy requirements for discharge computation:
• The combined accuracy of the total assemblage of instruments, equipment, and procedures…
• Are to be capable of sensing and recording stage with an uncertainly of no more than 0.01 ft or 0.20 percent of indicated reading
• The accuracy requirement for any single component generally will be more stringent than the requirement for the system as a whole.
• …Assessment of error magnitudes and of achievable accuracies of the various system components led to … the larger of 0.01 ft or 0.10 percent of reading as the accuracy standard for the procurement of … pressure-sensor instruments.
Radar measures stage as footprint of a variable area, dependent upon height of radar above water
Previous systems measure stage of a column of water above a point
Are measurements equivalent?
Timeline of radar stage sensors• 2004: ICOM
reorganized (elevator music here)
• 2005: Headquarters issues interim guidance requesting that field:– Does not purchase
instruments for widespread use
– Works with HIF for quality assurance testing of sensors that are purchased for unique situations
• 2005: HIF reports:Saturn rocket engine testing pad used for radar tests over water in early testing
Radars still purchased—Wouldn’t you if you had this gage?
Trace a ‘best guess’ of gage heights. In some cases the ‘peaks’ or ‘bottoms’ of the painting would be preferred. In painting like this, a trace at about mid-point is used.
• Brand X, model 1
• Brand Y (2 models)
• Brand Z, model 1
• Brand W (not shown)
Non Contact StageNon Contact Stage
4 Models Available4 Models Available
Stage Radars - 2005Stage Radars - 2005
Is Radar Good Enough (2005)?
• Brand X, model 1, problems with accuracy & FCC licensing
• Brand Y (USA), problems with accuracy• Brand Y (EU), problems with FCC licensing• Brand Z, Model 1, no SDI-12, accuracy is
promising
NO!NO!
• TWO commercially available models w/ 12 vdc & SDI-12
• Brand Z, Model 1
• Brand X, Model 1
• Both are pulse radars (FCC approved)
• Temperature tested
• Lab range tests underway
Radar Stage – New Models!Radar Stage – New Models!
• Vendor consulted with HIF on new unit development
• Pulse radar, low power
• Battery power (12vdc) & SDI-12
• Spec accuracy +/-0.01 ft <66 ft
• Units arrived early 2006
Radar Stage – Brand Z, Model 1Radar Stage – Brand Z, Model 1
New
Old
• Vendor has discontinued old model
• Demonstration sites at USGS Water Science Center stations
• Battery power (12vdc) & SDI-12
• Spec. accuracy of +/- 0.01 ft <32 ft.
Stage Radar – Brand X, model 1Stage Radar – Brand X, model 1
Walk-in ChamberWalk-in Chamber
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
0 50 100 150 200 250 300 350Ellapsed time in Hours
Dev
iati
on
in
fee
t fr
om
10
feet
of
stag
e
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
Tem
per
atu
re i
n º
C
SN 12643992 SN 12639922 (proto) Temperature
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.00 25.00 50.00 75.00 100.00 125.00 150.00 175.00 200.00 225.00
ELAPSED TIME IN HOURS
DIF
FE
RE
NC
E W
ITH
RE
FE
RE
NC
E
-50
-40
-30
-20
-10
0
10
20
30
40
50
TE
MP
ER
AT
UR
E IN
DE
GR
EE
S C
SN 1023 SN 1022 Temp
Temperature Temperature TestingTesting
Brand Z
Brand X, model 1
Is Radar Good Enough (2006)?
• Brand X, Model 1 accurate over temperature range.
• Brand Z, Model 1 working to improve units.
• Waves and sampling rates may affect accuracy.
• Air gap testing over larger ranges needed.
MAYBE!MAYBE!
Radar Measurement Questions
Do waves bias measurements low?
How does measurement timing & sample length affect accuracy?
Radar – Wave Effects
• Investigate effects of waves on sampling rate & accuracy
• Construction of wave generator
• Modification of existing test stand
• Horse Mesa Dam Reservoir drawdown fall 2006
• Brand X, Model 1.
• Brand Z, Model 1.
• Brand W
• Remote camera & weather instrumentation
• Instruments sent to AZ
• SRP making mounts
PlansPlans
Field Testing Partnership with SRPField Testing Partnership with SRP
•Accuracy check over large air gaps.
•Can Tow Cart be used?
Radar – Air Gap
Preliminary Air Gap Results
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.081
3-M
ay-
06
18
-Ma
y-0
6
23
-Ma
y-0
6
28
-Ma
y-0
6
2-J
un
-06
7-J
un
-06
12
-Ju
n-0
6
17
-Ju
n-0
6
22
-Ju
n-0
6
27
-Ju
n-0
6
DIF
FE
RE
NC
E w
ith
RE
FE
RE
NC
E i
n F
EE
T
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
HE
IGH
T A
BO
VE
in
FE
ET
H3611
Puls 62
Arm Height
Brand XBrand Z S
hould
be S
TA
GE?
Pearl River PierPearl River Pier
Radar Stage Measurement
Horn antenna
• Temperature may affect radar measurements.
• Sampling period affects measurement uncertainty.
• Radar possibly biased “low” for wavy conditions.
• Radar is less accurate when air gap increases.
• Site licenses can be needed for some radars
Findings So FarFindings So Far
Discussion