A system, apparatus, and method can tune a sensor to filter unwanted reflections or echoes of sound waves from a vegetation layer covering a ground surface in favor of reflections or echoes of sound waves from the ground surface. Such tuning can include adjusting a width of the sound waves output by the sensor. A distance from the sensor to the ground surface underlying the vegetation layer can be determined using the reflections or echoes of the sound from the ground surface based on the sound waves output from the sensor at the adjusted width.