Abstract: A control system for establishing grade and elevation control for a tool of a construction apparatus for maintaining the vertical position of the tool relative to a reference includes a first ultrasonic transducer configured to be carried by the construction apparatus, with the first transducer transmitting and receiving acoustic waves, at least one reflector, a second ultrasonic transducer configured to be carried by the construction apparatus, with the second transducer receiving acoustic waves, and a controller coupled to the first and second ultrasonic transducers which drive the transducers to produce an acoustic wave and monitors the time reflections of the acoustic wave are respectively received by the first and second transducers.

Abstract: A control system for establishing grade and elevation control for a tool of a construction apparatus for maintaining the vertical position of the tool relative to a reference includes a first ultrasonic transducer configured to be carried by the construction apparatus, with the first transducer transmitting and receiving acoustic waves, at least one reflector, a second ultrasonic transducer configured to be carried by the construction apparatus, with the second transducer receiving acoustic waves, and a controller coupled to the first and second ultrasonic transducers which drive the transducers to produce an acoustic wave and monitors the time reflections of the acoustic wave are respectively received by the first and second transducers.

Abstract: A digitally filtered laser receiver includes a plurality of radiation sensors spacially arranged in a manner which identifies a relative position of the sensors with respect to a rotating laser radiation source. The digitally filtered laser receiver includes a microcomputer having inputs which are responsive to impingement of the sensors by radiation. The microcomputer is programmed to process data from the inputs only when the radiation sensors are impinged by radiation from the rotating laser radiation source. The microcomputer processes the data and provides an output which is indicative of the position of the rotating laser radiation source and the sensors.

Abstract: A method and apparatus for controlling a trencher having a tractor that is propelled along terrain and a trenching implement adjustably mounted to the tractor at a rearward portion thereof with respect to movement of the tractor along the terrain includes monitoring movement of the tractor as it is propelled along terrain in order to survey the contour of the terrain and adjusting the position of the trenching implement with respect to the tractor as a function of the contour of the terrain in the vicinity of the trencher.

Abstract: An ultrasonic sensor for a construction implement is disclosed which provides an indication of the position of the sensor relative to a reference surface in two dimensions. In a preferred embodiment of the invention, a pair of sensors are positioned a predetermined distance from one another to transmit and receive ultrasonic waves to measure the time it takes the waves to travel to the reference surface and be reflected back to the ultrasonic transducers. Additionally, a transducer is disclosed which detects a side lobe of a acoustic wave transmitted by an acoustic transducer whereby the velocity of said acoustic pulse may be calculated.

Abstract: An ultrasonic sensor for a construction implement is disclosed which provides an indication of the position of the sensor relative to a reference surface in two dimensions. In a preferred embodiment of the invention, a pair of sensors are positioned a predetermined distance from one another to transmit and receive ultrasonic waves to measure the time it takes the waves to travel to the reference surface and be reflected back to the ultrasonic transducers. Additionally, a transducer is disclosed which detects a side lobe of a acoustic wave transmitted by an acoustic transducer whereby the velocity of said acoustic pulse may be calculated.