Project Title:

Low-Cost Global-Positioning System and Inertial Mapping System

92-1-14.04-4887                                                     NASW-4784
Low-Cost Global-Positioning System and Inertial
     Mapping System
Navsys Corporation
14960 Woodcarver Road
Colorado Springs, CO  80921
Alison K. Brown                                      (719-481-4877)

Abstract:

     This project combines an inertial instrument with the Global-
Positioning System to make a GPS-inertial mapping (GIM) system
that will be capable of providing sub-meter performance even
during periods of satellite shadowing. This is achieved through
the use of an innovative differential-carrier-ranging (DCR)
algorithm that computes a highly accurate position solution
(<0.15m) when four satellites are visible. To achieve high
accuracy during periods of shadowing, an innovative estimator and
smoother algorithm will be developed to calibrate the inertial
errors. Preliminary simulation results have demonstrated that this
improves the inertial position data by more than an order of
magnitude over a conventional GPS-aided Kalman filter. The
combination of the DCR and estimator and smoother algorithms
allows the GIM to provide submeter accuracy during unaided GPS
operation for up to 100 seconds, using low-cost, miniaturized
inertial instruments (e.g. 0.1ø/ûhr gyros). Phase I will provide
simulation results on the DCR and estimator/smoother performance.
A trade study will also be performed of suitable inertial
instruments for use in Phase II. A preliminary survey has
identified a candidate micromechanical inertial measurement unit
(IMU) with a projected cost of $500 in quantities of 10,000. Phase
II will integrate the selected IMU with a miniaturized GPS
receiver and demonstrate the GIM system performance.

Potential Commercial Application:

Potential Commercial Applications:  The GIM system allows
uninterrupted mapping data to be collected even during periods of
temporary GPS signal outages. This permits highly accurate,
continuous, automatic data collection to be carried out from
moving vehicles. A wide variety of commercial applications exist
for the GIM as a data collection system for geographic information
systems (GIS).

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