Within the scope of the project VarIoNav, a scientifically based and comprehensive investigation of the integration of GPS and inertial measurement systems (IMS) is performed. For this purpose, GPS-receivers and inertial measurement units of different quality and price classes are to be compared in a lot of possible combinations. The type of integration not only depends on the quality of the involved sensors but also on the coupling method within signal processing. Due to the used filtering technique, an uncoupled, loosely coupled, and tightly coupled integration of GPS and IMS can be performed.
As a primary result of the investigations, a classification of the integration types with respect to usability, accuracy, and reliability is expected. The two latter quality measures are related to positioning and attitude determination. Regarding the high value of GPS-IMS fusion within integrated navigation, the integration analysis is performed against the background of the challenging trajectory determination for a mobile exploration system (e.g., imaging sensors, active or passive) and the subsequent direct georeferencing of the sensor and its output.
For the purpose of direct georeferencing, the methods of the comparative analysis of GPS-IMS-integration are based, within VarIoNav, both on simulations and experimental (field) tests for measurement and imaging platforms.
The determination of the earths gravity field is an essential tool for many scientific disciplines. While satellite missions can be used to determine the long wavelength character of the earths gravity field, terrestrial measurements provide the high frequency part of the local and regional structure.
One method to determine the regional gravity field is the use of airborne gravity mapping systems. Through the fast technological progress during the last decades a new concept of airborne gravimetry could be applied for the first time around 1995. Instead of using a gravimeter mounted on a horizontally stabilized platform, Carrier GPS and a strapdown inertial system were put together in a sensor platform.
The GNSS/INS combination for determining the earths gravity field is not restricted to airborne applications. It may be adapted for terrestrial use where the platform will be mounted on a vehicle moving on the earths surface (e.g. ships or cars). The gravity measurement by a moving car is a fast and cheap alternative to airborne and terrestrial gravimetry. The method can especially be applied for the densification of gravity measurements in complicated regions with sparse gravity distribution. As a result line-based measurements will be gained.
The Institute of Navigation and Satellite Geodesy is the only institute in Austria having a high precise IMU. In combination with the GNSS equipment of the institute a platform equipped with a GNSS/SINS can be set up. This opens the field to comprehensive investigations for the use of GNSS and inertial techniques for moving gravimetry using cars as a vehicle.