The Measurement of Altitude and Inclination of Aircraft by the Echo Method

Citation

Delsasso, Leo P. (1941) The Measurement of Altitude and Inclination of Aircraft by the Echo Method. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/7v7a-rk28. https://resolver.caltech.edu/CaltechTHESIS:03282025-211325615

Abstract

During the past twenty years the Echo Method of measuring distances has been successfully employed by surface ships both for charting and navigating. The present investigation was undertaken in order to determine the advantages and limitations of the parallel application of measuring the altitude of modern aircraft.

Although similar in principle these two applications involve different problems. Some of these arise from the different media in which the sounds are transmitted, some from the vastly different velocities involved and others from the different disturbing influences in the two cases. The investigation has been divided into four parts.

The first section of the paper is devoted to a theoretical examination of the sound waves transmitted from and received on a moving ship. Expressions are derived for the Doppler Effect as a function of the inclination of the reflecting surface and the ratio of ship velocity to that of sound.

The second section is devoted to the corrections introduced by the speed of the ship, its direction relative to the reflecting surface and the temperature. It is shown that, for practical purposes, these corrections can be made from observations in the ship.

A third section is devoted to the measurement of the sound spectra of typical ships in flight and to the attenuation of sound in the atmosphere.

A fourth section describes an experimental altimeter together with the results of field tests in the Goodyear Airship "Volunteer". Altitudes as great as 700 feet and as low as 4 feet were measured. Subsequent work indicates that in order to obtain a maximum range of 1000 feet under unfavorable atmospheric conditions a source radiating 500 watts of acoustical energy is required.

Thesis Files