brochure · English
Description of Ground Position Indicator Type A-1
This document describes the Ford Instrument Company Ground Position Indicator (GPI) Type A-1, a four-unit airborne system prepared for the U.S. Air Force that continuously computes and displays present latitude and longitude of an aircraft in flight. The system weighs approximately 45 pounds (exclusive of cables), operates from 115 V 400-cycle and 28 V DC power, accepts true airspeed, compass heading, wind direction, wind force, and magnetic variation inputs, and achieves a maximum total air-position error of about 1.5% of computed nautical miles traveled. The document covers operating principles, component descriptions (Preset Control Box, Computer Unit, Amplifier Unit, Ground Position Indicator panel), dimensional drawings, and the trigonometric geometry underlying the latitude/longitude integration.