Transcript KIISSELI Projekti: DSC111 ja kitka

Road Weather
Sensors
Road Weather, Vaisala Solutions
Taisto Haavasoja
Concept of Ice Warning and Prediction on Highways
C
Thermal mapping
km
One-time
measurement
USER
INFORMATION
COMPUTER
C
SYSTEM
+
ROSA /
Road surface
analysis
ICECAST
t
On-line
real-time data
SOFTWARE
Actual road state
on color map or
data table
Salting Route
Optimization
Road status
warnings/alarms
Road icing
forecast map
Salting conditions
3h
6h
12 h
2
5
3
CLOUDS 0
2
3
TEMP.
Road weather forecast
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24 h
forecast
RAIN
-
LR
-
WIND
4
2
0
Statistics
Training, Service,
HelpDesk
Road Weather Station
• Monitors:
– road surface conditions
– e.g. icy, wet, dry
– road temperature
– road weather conditions
– precipitation
– air temperature, humidity, dewpoint
– wind, pressure, etc.
• Warns of:
– icy road surface
– frost or precipitation
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Typical Sensors in a Road Weather Station
Atmospheric sensors:
•
•
•
•
air temperature, humidity, dew point
precipitation, present weather
wind speed and direction
pressure, radiation, ...
Road sensors:
• surface temperature
• surface condition
– ice, water, snow and how much
– salt amount, concentration, depression of
freezing point (DFP)
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Road Surface Sensors in Testbed
Road Surface Condition Sensor DRS511
•
•
•
•
surface temperature
surface condition
salt amount, salt concentration and
depression of freezing point
Road Surface Temperature Sensor DST111
• infrared remote thermomometer
Road Surface Condition Sensor DSC111
• optical detection of ice and snow or frost
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Vaisala’s Road Surface Condition Sensor DRS511
Black Ice
Detection
Measurement of
Conductance
and Polarization
Optical
Measurement of
Layer Thickness
Surface
Temperature
DRS511
Multi-Sensor Block
Ground
Temperature
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DRS511 Coverage Detection
• Optical coverage detection is based on three fibre optics; one
is transmitting and two are receiving.
• The two reflected signals determine the water layer thickness
(in mm) or the presence of snow on the sensor.
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Salt Amount, Concentration and DFP
Most common deicer is still rock salt (mostly NaCl)
• occasionally also CaCl2 is used
Salt amount (s) is measured in grams per square meter (g/m²)
Water or ice layer thickness (t) is measured in millimeters (mm)
• 1 mm of water equals to: 1 kg/m² = 1 liter/m² = 1 mm m²/m² = 1 mm
We get salt concentration as: c = s/t [(g/m²)/mm] = s/t [g/l]
Depression of freezing point: DFP = f(c)
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Depression of Freezing Point
20
Non Saturated Brine
Salt and Saturated
Brine
T (C)
10
1. DFP
0
-10
2. Surface becomes
slippery here
Dihydrate and
Saturated Brine
Ice and Saturated
Brine
-20
3. All liquid frozen
0
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20
x (%NaCl)
40
New Approach to Road Weather: Remote Sensing
Surface Condition
Surface Temperature
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Vaisala Remote Road Surface Temperature Sensor DST111
Properties
•
•
•
•
remote sensor, no installation in the road
measures also under heavy traffic
measures also air temperature and humidity
accurate remote road surface temperature measurement
– unique compensation of reflection errors
– estimated accuracy of surface temperature
– 1 °C within -20 ... +10 °C and with solar radiation < 200 W/m²
– about 0.3 °C in typical icing conditions
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Vaisala Remote Road Surface Condition Sensor DSC111
Properties
• surface condition
– dry, moist, wet
– snowy/frosty, icy, or slushy (wet snow)
– independent measurement of
– water, ice and snow/frost layer thicknesses
• friction
– slipperiness is output as a friction coefficient
• easy installation and service
– no asphalt cutting, easy traffic control
• measures reliably even under heavy traffic conditions
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DSC111 Performance in Freezing Drizzle 09.01.2006
Freezing Drizzle at Vt6 Imatra, 2006-01-09
0.90
Dry
Grip or Layer Thickness (mm) )
0.80
Moist
Wet
0.70
Wet/s
0.60
Frost
0.50
Snow/Frost
Ice
0.40
Slushy
0.30
Warning
0.20
Alarm
Twater
0.10
Tice
0.00
12:00
14:00
16:00
18:00
22:00
0:00
Tsnow/frost
Frict.VB
-0.10
Time (hh:mm)
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20:00
DSC111 installed in a car
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Highway 3, Helsinki 06.03.2006
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Ring Road 3, Helsinki 06.03.2006
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Side Road in Helsinki 06.03.2006
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DSC111 Friction compared to Actual Measured Values
0.90
0.80
DSC111 Friction
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
0.10
0.20
0.30
0.40
0.50
Measured Friction
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0.60
0.70
0.80
0.90
Summary
• Effective winter maintenance will result increased safety with reduced costs
• Road weather information system is the key component in achieving that
target
• Vaisala is the world leader in road weather systems
• Vaisala’s unequaled Remote Road Surface Condition Sensor DSC111
measures friction coefficient reliably
• look at further details in
– Proceedings of the SIRWEC 2006, page 13.
– http://www.vaisala.com/
– http://www.vaisala.com/weather/dsc111
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