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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