ABSTRACT

          "In the 1950's, a small group of students and researchers, working at Princeton University under Robert H. Dicke, probably first gave substance to the concept of what would become the technique of optical laser ranging [Alley, 1972]. In an attempt to probe the fundamentals of gravity, they suggested that powerful, pulsed searchlights on the Earth be used to illuminate optical corner retroreflectors placed upon an orbiting artificial Earth satellite. One could then precisely analyze the orbital characteristics of that satellite's motion by photographing its position against the background of fixed stars. The invention of the laser, with its precise wavelength and beam divergence characteristics, coupled with the technique of Q-Switching to produce laser pulse lengths on the order of only a few nanoseconds, caused a re-thinking of the artificial satellite photography experiment and ushered in the era of optical laser ranging. Procedures similar to those which were performed with microwave radars were upgraded to provide optical range measurements that had remarkable precision and accuracy. The initial such laser-to-target-and-return time-of-flight experiments were made at the NASA Goddard Space Flight Center in Greenbelt, Maryland in the mid-1960's. Degnan [1993] has recently reviewed U. S. artificial satellite ranging efforts."

          This project in its present form is the result of experimentation on the interfacing of an electronic device which communicates with a computer through the serial port. Previously success has been obtained in applying the idea of ranging mechanically without any computer.

For calculating the height of any object the angles are measured by the serial device itself which remain attached to the computer’s serial port.

This serial device can calculate the angles subtended by the object’s length quite accurately. To calculate the angle the computer calculates the rotation of a shaft driven by a gear train. By using the gear train we have been able to magnify an angular rotation significantly. Using these angles we can then calculate the height of the object. This device with a computer can be used to measure the height and can also be used for measuring the under water heights. One of the major advantages of this device is that it can be used at night as well.