IMUVar - GRAVIS - Terrestrial Moving-Base Gravimetry Using a GNSS/SINS Platform

The GNSS/SINS combination may be adapted for terrestrial use where the platform will be mounted on a car. The gravity measurement by a moving car is a possible alternative to airborne and terrestrial gravimetry. This method can especially be applied for the densification of gravity measurements in complicated regions with sparse gravity distribution. Within the project GRAVIS a demonstrator for determining the Earths gravity field by using a car will be built.

Short Description

One method for the determination of the regional gravity field is the use of airborne gravity mapping systems. Today receivers based on Global Navigation Satellite Systems (GNSS) and strapdown inertial systems (SINS), mounted on a multi-sensor platform are used.

One task of the project is the stable determination of accelerations from GNSS measurements, which can be influenced by the difficult surrounding in the case of terrestrial applications like cycle slips, multipath and shadowing effects. Another critical task is the error analysis of the terrestrial application which will need a more complex discussion of the error terms compared to the airborne case.

In principle, the error of the gravity vector for the strapdown inertial gravimetry is mainly a function of the attitude errors due to the initial misalignment and gyro measurement noise, the accelerometer noise, errors of the determination of the vehicle acceleration by GNSS and a synchronization error between the SINS and GNSS system. The SINS uses ringlaser gyros and servo accelerometers.

An innovative approach is the concept of using an antenna array to support the gyro measurements in order to compensate the gyro readings for the drift behavior. The concept of the GNSS/SINS combination is based on the fundamental equation. There the specific force measured by the accelerometers of the SINS is the difference between the inertial acceleration of the vehicle and the gravitational acceleration.

That means if the inertial acceleration of the vehicle can be determined with GNSS, the gravity can be directly obtained. The task of GNSS is the determination of the vehicle’s acceleration as well as the vehicle’s velocity and position. In principle, a double differentiation of the position is needed. Errors of the vehicle acceleration are directly proportional to the gravity error.

Project Partners

Coordinator

Graz University of Technology, Institute of Navigation and Satellite Geodesy - Prof. Norbert Kühtreiber

Contact Address

Graz University of Technology - Institute of Navigation and Satellite Geodesy
Prof. Norbert Kühtreiber
Steyrergasse 30
A-8010 Graz
E-Mail: norbert.kuehtreiber@tugraz.at
Web: www.inas.tugraz.at