TABLE OF CONTENTS Descriptions of aids to navigation presented in this chapter include the following:
Doppler velocity sensors (DVS).
Tactical air navigation (TACAN) range.
Global positioning systems (GPS).
Forward looking infrared (FLIR) and other line-of-sight (LOS) systems.
These systems provide independent redundant navigation information that can aid an integrated navigation system via the Kalman filter algorithm.
Doppler velocity sensors are used widely in aircraft, seacraft, and land vehicles. While operating with different mechanizations, e.g., radar, acoustic, laser, etc., most employ the Doppler shift principle. A simple characterization of a Doppler system's operation, performance characteristics, and development of error modeling approaches, assuming the navigation system error model representations defined in Chapter 5, is presented.
GPS operates on a satellite-to-receiver/antenna ranging principle. This is functionally similar to the principle of operation for TACAN. TACAN ranging is used with respect to a fixed ground station, while GPS ranging is used with respect to a satellite whose position is known relatively accurately. In this presentation, TACAN is used to illustrate a single ranging operation that is extended to multiple satellite ranges for GPS.
Presented are Keplerian equations that describe satellite orbital motion and are used in the GPS receiver's processing to determine the satellite positions in an Earth-centered, Earth-fixed (ECEF) frame. Quality measures associated with GPS data are used to determine which satellite's ranging data are to be used. The satellite elevation and geometrical dilution of precision (GDOP) quality measures are developed.
Airborne line-of-sight systems include radar, FLIR, television (TV), etc. These systems serve many functions,...
