Position, velocity, and attitude information are crucial in many kinematic geodesy and navigation applications. Traditionally, an Inertial Navigation System (INS), a self-contained measuring unit, has provided this information. The INS consists of an Inertial Measurement Unit (IMU) and computer/software that processes the raw IMU measurements.

The IMU, comprising accelerometers and gyroscopes, measures motion based on physical laws of nature, while the computer performs the mathematical integration operations. The basic concept of INS navigation computation is to integrate the acceleration vector sensed by the accelerometers to determine velocity and position. However, the stand-alone INS positioning accuracy deteriorates rapidly with time due to its double-integration mechanisation algorithm.

In contrast, GPS provides accurate position, velocity and time data without any impact of mission length or time since update. The main factor limiting the use of GPS is the requirement for line-of-sight between the receiver antenna and the satellites. Additional shortcomings include the low data output rate and the need to deploy more than one GPS antenna in order to obtain full attitude information (e.g., heading, pitch and roll). Because of their complementary natures, integrating INS with GPS (and/or pseudolites, which are "pseudo-satellites") can arguably leverage the advantages of each sensor system.

The advantages of GPS/INS integration, relative to either GPS or INS alone, are:

Hence, these systems have been used for a wide range of applications, such as aerial photogrammetry and gravimetry, mobile mapping, vehicle navigation, guidance and control. This web page summarises the research activities at the School of Surveying & Spatial Information Systems, UNSW, that deal with the integration of GPS (and/or pseudolite) with INS, as well as providing links to some useful web resources and manufacturers' sites.

SNAP Research Activities:

1. SATNAV Toolbox v3.0 is a collection of M-files which allows for total system emulation of satellites, receivers, and propagation channels. The Toolbox allows the user to emulate the C/A-code on L1, L2, L5 and any other user defined frequency. In addition the toolbox can be used to simulate P-code on L1 and L2. The toolbox has recently been upgraded to handle the processing of real receiver data files in RINEX format.
2. INS Toolbox Version 2.0 extends the capabilities of the original toolbox with a number of key features. Among these are a non-linear 6DOF flight profile/trajectory generator, a land vehicle trajectory generator, an improved delta-theta measurement emulator, and functions that allow the user to define a dynamic trajectory in a local-level coordinate frame and then perform a full INS simulation in the rotating earth frame. Raw measurements (delta-V's and delta theta's are generated and typical error sources (gyro and accelerometer biases, scale factor errors, noise and initialization errors) are emulated. The Toolbox is fully compatible with the SatNav Toolbox to allow for integrated system analysis and simulation.
3. Navigation System Integration and Kalman Filter Toolbox extends the capabilities of the GPSoft SatNav and INS toolboxes by providing the Kalman Filter algorithms used to achieve maximum performance. Among these are GPS stand-alone 8-State and 11-State extended Kalman filters, inertial error modeling in state-space, loosely-integrated INS/GPS Kalman filters, and tightly-integrated INS/GPS Kalman filters. The Toolbox is fully compatible with (and actually requires both) the SatNav and INS Toolboxes.

Web Resources:

Manufacturer's Sites: