PERFORMANCE OF AN ULTRASONIC LEVEL SENSING SYSTEM FOR AUTOMATED MONITORING OF SNOWCOVER DEPTH

The operating characteristics of a commercially available ultrasonic level measuring system is described. The objective was to test the applicability of the system to automatically monitor depths of snowcover as part of a fully automated weather station. With temperature compensation, the system is relatively stable when the time rate of change in temperature is below 8-degrees-C h-1, a value that rarely occurs in the natural environment. Measured depths are relatively unaffected by relative humidity, wind velocity, and rain. Spatial average of snow-cover depths measured with the system at seven locations compared favourably with that measured with snow rulers, with a correlation coefficient greater than 0.95. Using three standard deviation limits, the imprecision of the system as compared with the snow rulers is +/- 0.72 cm. A simple electro-mechanical scanner was used to interface sonic transducers to a single electronic measuring unit. With such an interface, additional point measurement of snowcover depth may be achieved with a relatively small amount of added cost. Low cost together with accuracy and reliability makes this system very attractive for use in automatic weather observations in agricultural and forestry applications.