Preliminary conclusions on application of ultrasonic sensors in evaluation of distribution and depth of ruts in forest thinning
Latvian State forest Research Institute 'Silava', Rīgas street 111, LV-2169 Salaspils, Latvia
The scope of the study is to elaborate equipment for measurement of ruts during log forwarding. The system is supposed to be used in practical forestry to replace manual measurement of length of deep ruts and to provide spatially explicated information on soil bearing capacity, which can be used in planning of forest operations.
A set of 4 pairs of ultrasonic sensors were installed on front and rear bunks to measure distance to the ground at 90o angle (in front and behind the wheels in each side of forwarder) and at certain angle to measure distance to the ground outside strip-road. Measurement data are sent to the logger, where they are stored in .csv files. Wired connection between the sensors and the logger was used in earlier version, but later replaced with wireless connection. Depth of rut is calculated using formula for calculation of length of cathetus of a right-angled triangle. Data processing in spreadsheet includes initial identification of error values and calculation of depth of ruts. Further spatial data analysis is done in GIS software.
According to the study results ultrasonic sensors provides sufficient accuracy to characterize depth of ruts in 1…5 m long segments of strip-roads, including dynamic data on depth and length of ruts after each pass. However, the accuracy is insufficient to compare measurements from sensors mounted on front and rear bunks, as well as on left and right side of machine, therefore it is enough to have 2 pairs on sensors on rear bunks.