The SR50 snow depth sensor has an ultrasonic pulse measurement cone
of 22 degrees from the bottom of the sensor to the target. The sensor measures the distance from the sensor to the target (in this case it is the ground surface or snow surface). To calculate snow depth, this distance to target measurement is subtracted from the field measured distance to ground surface. Currently, the sensor records measurements at
one minute intervals and reports hourly averages. Potential
inherent errors exist; since the speed of sound
is affected by the temperature of the air it is traveling in, an
air temperature measurement is required to correct the distance
reading. Physically related errors include wind and blowing snow creating
spurious data readings, difficulty in establishing a zero point due
to tussocks, low shrubs, grass, etc., ground heave altering sensor
height and angle, as well as cable breakages due to wildlife. Research is underway to improve the measurement with moving averages and weighting schemes. |
