Browse Prior Art Database

Global Positioning System Receiver Simulation

IP.com Disclosure Number: IPCOM000112187D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 6 page(s) / 185K

Publishing Venue

IBM

Related People

Rapp, JW: AUTHOR [+2]

Abstract

A system for simulating a Global Positioning System (GPS) receiver for a trainer is disclosed. The simulation utilizes stochastic processes and instructor controls to emulate the observable effects and dynamics of the GPS Satellite Constellation and the Receiver.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Global Positioning System Receiver Simulation

      A system for simulating a Global Positioning System (GPS)
receiver for a trainer is disclosed.  The simulation utilizes
stochastic processes and instructor controls to emulate the
observable effects and dynamics of the GPS Satellite Constellation
and the Receiver.

      The problem was to insert a new GPS simulation function into a
preexisting trainer.  The avionics system needed to be fooled into
operating properly without the actual onboard GPS equipment.
Students needed to be convinced of the proper fidelity for the GPS
navigation functions and malfunctions.  Instructors needed to be able
to control the student training via a number of specific
malfunctions.

      Simulating the 24 satellite positions, each orbiting once every
12 hrs., was determined to be too complicated for practical software
implementation.  Additionally, the effects of aircraft roll needed to
be modelled in response to pilot or instructor maneuvers.  The
effects of GPS navigational errors needed to be modelled as well.

o   Bias Error - A small offset error, normally remaining a constant
    throughout the flight.

o   Key Loss - The GPS navigation error or lack of accuracy due to
    loss of the Military Decryption Key.

o   Geodesic Determination - The GPS navigation errors due to poor
    receiver/satellite geometries.

o   Satellite Reception - The GPS navigation errors due to loss of
    the signal from one or more satellites.

o   Lastly, the student operators were to be allowed to initialize
    the GPS receiver with a current position, date and time which
    resulted in

1.  the GPS receiver converging to an accurate navigation solution,
    or

2.  an erroneous and diverging navigation solution.

      The GPS simulation function will be demonstrated by using a
trainer.  In particular the Navy Helicopter Weapons System Trainer
(WST) will be used for descriptive purposes.  Fig. 1 shows a block
diagram for the new GPS simulation function, which was inserted into
a preexisting Navy Helicopter Weapons System Trainer (WST).

      The four outer blocks (dash line connected) represent
preexisting software functions of the WST.  These blocks are
described below.

      Instructor Controls And Displays (IC&D) Software Support - This
software provides the operator machine interface for the WST
Instructors.  A new screen was added for GPS controls.

      Dynamic Position - Dynamic motion models are provided for all
vehicular entities.  This software provides all positional, velocity,
and acceleration data for the simulated helicopter, as controlled by
either the instructor or the pilot.

      Remote Terminal Interface System (RTIS) - This software
function provides real time interfaces with the actual avionics
equipment which is retained in the WST.  The GPS emulation primarily
occurs via 1553B data bus communications with the actual avionics
co...