IMPROVING%20RELIABILITY%20AND%20SENSITIVITY%20OF%20A%20LASER%20SNOW%20DEPTH%20GAUGE

1
IMPROVING RELIABILITY AND SENSITIVITY OF A LASER
SNOW DEPTH GAUGE

• Eckhard Lanzinger and Manfred Theel, Deutscher
  Wetterdienst (DWD)

2
Comparison of ultrasonic and laser snow depth
gauges

• 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 lt 0.5 cm no
  temperature compensation needed insensitive to
  snowfall and wind

Experimental setup
Laser gauge provides backscatter signal
3
Snowfall event on 23. January 2009 (Hamburg)
1207 Onset of light / moderate snowfall
wawa (Tab. 4680)
1305 SHM 30 signal strength gt 3.5
1415 SHM 30 snow depth gt 0.5 cm
SHM30 backscatter signal
SHM30 snow depth
1714 SR50 - snow depth 1cm
SR50 (corrected 5 minute mean)
Backscatter signal allows early detection of snow
cover
4
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.
5
Operational Experience
Both laser points were about 10 cm apart
Very good correlation of two laser gauges and no
zero drift
6
Multipoint Measurement

• Manufacturers should think about a scanning laser
  snow depth gauge to cover larger areas

7
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

Thank you for your attention!