GAL
GAL: GALILEO for Gravity

Airborne gravimetry is considered an efficient and cost effective means of providing accurate high-resolution gravity data.
A stand-alone airborne gravimetry survey provides a trajectory with 20/30cm accuracy, which implies gravity recovery of 15mGal or a geoid with accuracy of 20cm.

With the use of Galileo, EGNOS and GOCE performances can be improved to 0.1 mGal accuracy on spatial scales of 10 km.

These measurements allow areas with poor data coverage to be surveyed in an effective way.

Why this project is important for EGNOS/GSA/SatNav?

The valorisation of European assets (GOCE, EGNOS and Galileo) by developing an innovative methodology for precise and high resolution gravity measurement is of strong scientific and public interest.

Objectives

The GAL project aims to study and develop a state-of-the-art methodology to determine precise and high-resolution gravity field models.

The key issue is the precise Kinematic Airborne Gravimetry (KAG), with the joint use of most recent techniques and technologies, such as EGNOS, GPS, Galileo and strapdown Inertial Measurement Units (IMUs), and its further integration with GOCE global models.

KAG is, in fact, the most promising alternative to very expensive, slow and troublesome terrestrial surveying; it requires the measurement of the gravity field on a local and global scale.

GNSS measurements provide a practical way to separate the gravitational quantities from kinematic accelerations (linear and/or angular). KAG-GNSS/INS uses the IMU as a gravimeter and the GNSS receiver to determine the geometric accelerations.

In the last decade, the limitations of the GPS system (need for dense ground infrastructure, accuracy limitations and carrier phase noise) have strongly limited the operational exploitation of KAG-GNSS/INS. Gravity recovery from airborne surveys, in fact, is mainly affected and limited by the noise related to GPS-derived accelerations.

But nowadays crucial improving technologies have been furnished by European GOCE, EGNOS and Galileo, so the KAG methodology can now become a reality.

How does it work?

The GAL concept foresees the combination of satellite-derived global gravity models (using GOCE) with airborne-derived local models (using airborne EGNOS/GNSS/INS). While GOCE gradiometry will resolve the gravity field with an accuracy of 1-2 mGal and a geoid accuracy of 1-2 cm at 100 km wavelengths and longer, airborne gravimetry will resolve, with comparable accuracy, the gravity field with resolutions ranging from 200 km to 1 km.

Next Steps

The first workshop, to be held in May 2013 in Como - Italy, will present the first results and outline the next steps.