Engineering topics

Van Graas, F.

Publications and source records attributed to Van Graas, F..

3 records

NASA NTRS1990

Tests Of A Differential Global Positioning System

Paper describes validation tests of global positioning system (GPS) for low-flying helicopters. Configured as differential GPS, in which components in both aircraft and ground station compute position errors relative to known location using satellite navigational data. Corrections computed from differences between computed and measured ranges to four satellites being tracked by receiver in both aircraft and ground systems. Tests conducted to determine whether equipment and computer programs of system operated correctly and consistently.

Edwards, F. G.↗

NASA NTRS1988

Validating the airborne and ground based components of a differential GPS system

A differential GPS mechanization of an external data link concept under development at NASA Ames Research Center is discussed. The system is intended to evaluate the use of differential GPS to support helicopter approach operation. Analytical techniques for static testing and evaluation of the system hardware and software performance in real time are described. Several techniques that have been used to detect and rectify a specific problem encountered during the tests are dicussed. An example of flight test results using the validated system is provided.

Edwards, F. G.↗

NASA NTRS1986

Architecture and performance of a real time differential GPS ground station

The NAVSTAR Global Positioning System (GPS) is a satellite based navigation system that can be operated in a differential mode. The basic concept of differential GPS is to have a local ground station at a known location. The ground station continuously determines bias corrections based on the received satellite signals and transmits these corrections to local users. This allows the user to improve significantly their estimate of position. The architecture of a real time differential GPS ground station based on two STI (Stanford Telecommunications, Inc.) single-channel GPS receivers is presented. Receiver requirements are described, together with the receiver architectures. Real time operation results are presented for recent data collected from six satellites.

Turner, R. N.↗