Introduction

 

There is a need for an inexpensive altimeter to facilitate the landing of small, non-commercial seaplanes on lakes.  Most small non-commercial airplanes are equipped with barometric altimeters.  In order to obtain accurate readings, these altimeters must be calibrated in reference to the air pressure at a landing site.  Since this can only be accomplished when there is a radio tower located in the landing site vicinity, with an operator who has the tools necessary to read atmospheric pressure, a barometric altimeter is not able to provide accurate readings for bush pilots landing in remote locations.

 

There are other options available to determine altitude in regions where barometric altimeters are not feasible.  Some alternatives include laser and radio rangefinder devices. Laser rangefinders are very accurate, even over distances of 400m. Commercial laser altimeters are available for approximately $3500 USD [2].  Using Radio technology for altimeters is the oldest and one of the most common methods in aviation and research today. Radio altimeters are extremely accurate, and can operate under hugely ranging temperatures and atmospheric conditions.  However, they are also highly expensive.  Both of these instruments are simply too costly for many pilots to justify their purchase.

 

In most situations, it is possible for bush pilots to land by gauging the distance to ground with their eyes.  However, when landing on a lake on a calm day it is difficult to gauge where the surface of the water is, due to the waterıs high reflectivity.  The method currently employed to aid pilots in landing is to throw an item from the window of the plane in order to see the ripples on the lake [1].

 

The aim of this project is to determine the feasibility of employing a sonic ranging device as an altimeter. This altimeter should have a range of 0-40 m, with an accuracy of 10cm [1].