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Titelfoto auf dem Titelmaster einfügen
Deutscher Wetterdienst
IMPROVING RELIABILITY AND SENSITIVITY OF A LASER SNOW DEPTH GAUGE
Eckhard Lanzinger and Manfred Theel, Deutscher Wetterdienst (DWD)
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Comparison of ultrasonic and laser snow depth gauges
Experimental setup
Campbell SR50G (ultrasonic)
■ sonic cone with angle of aperture: 12°
■ vertical measurement
■ measurement uncertainty: 1% of distance
■ needs temperature compensation
■ sensitive to snowfall and wind
Jenoptik SHM30 (laser)
■ small red laser beam
■ slanted measurement at an angle of 30°
■ measurement uncertainty: < 0.5 cm
■ no temperature compensation needed
■ insensitive to snowfall and wind
Laser gauge provides backscatter signalLaser gauge provides backscatter signal
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Snowfall event on 23. January 2009 (Hamburg)12:07 Onset of light / moderate snowfall
14:15 SHM 30 – snow depth > 0.5 cm
13:05 SHM 30 signal strength > 3.5
17:14 SR50 - snow depth ≥ 1cm
SHM30 backscatter signalSHM30 backscatter signalSHM30 snow depthSHM30 snow depth
SR50 (corrected 5 minute mean)SR50 (corrected 5 minute mean)
wawa (Tab. 4680)wawa (Tab. 4680)
Backscatter signal allows early detection of snow coverBackscatter signal allows early detection of snow cover
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Operational Experience
Backscatter signal varies from gauge to gauge. Signal level should be calibrated and adjusted at the factory
Grey snow plate improves snow cover detection
Heating of housing has to be improved for icing conditions
Visible laser point can attract birds
Comparison of two Laser snow depth gauges JENOPTIK SHM30.
Icing problem of JENOPTIK SHM30.
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Operational Experience
Very good correlation of two laser gauges and no zero driftVery good correlation of two laser gauges and no zero drift
Both laser points were about 10 cm apart
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Multipoint Measurement
Manufacturers should think about a scanning laser snow depth gauge to cover larger areas
DWD / E. Lanzinger TECO-2010, 30. August – 1. September 2010, Helsinki, Finland
Thank you for your attention!
Conclusions
Positive features of Laser snow depth gauges ■ Slanted measurement with high accuracy ■ Practically independent of air temperature and wind ■ No drop outs even during heavy snowfall
Detection of snow cover by backscatter signal ■ Sensitivity increased ■ Reliability of snow depth measurement increased
Possible improvements ■ Backscatter signal strength has to be calibrated ■ Multipoint measurements