An opto-electronic soil profile meter

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Virginia Polytechnic Institute and State University

A mechanical, non-contact soil profile meter was developed to measure soil elevations before and after an artificial rainfall for erosion studies. The design goals were to measure the heights of the soil in a 1.5 x 1.5 m bin with an accuracy of ±1.0 mm and at a data collection rate of 2 points per second.

The profiler consisted of a laser and a digital camera for height measurements, and a drive system for horizontal movement. The device was calibrated to determine the accuracy of horizontal positioning and the error associated with the height measurements. The positioning accuracy of the profiler was ±0.12 mm and the calibrated height error was ±0.68 mm. The rate of data collection was 32 points per minute.

The calibrated height measurement unit was tested with actual soil samples. The analysis of the data collected from 9 different soil colors at 3 different heights and 5 different locations along the profiler indicated that color, rod deflection, and vertical distance between the lens and the surface affected the height measurements. The error for absolute heights was 1.2 mm and the error for the difference in heights was 0.2 mm.

The outdoor performance of the profiler was also checked and the result was satisfactory.