GAL project

Study and development of a new methodology for the determination of high-resolution local gravity models by airborne gravimetry.

GAL project website

«GAL – Galileo for Gravity» is a two-years project co-financed by the GSA – European GNSS Agency in the frame of the FP7 Transport theme. GAL project aimed at the study and development of a state-of-the-art methodology for the determination of 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 one of the most promising alternative to the very expensive, slow and troublesome terrestrial surveying; it requires the measurement of the gravity field at the 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 for the determination of the geometric accelerations.

Furthermore, the GAL concept foresees the combination of satellite-derived global gravity models with airborne-derived local models. While the GOCE gradiometric measurements will provide the global gravity model, the airborne EGNOS/GNSS/INS ranging and inertial measurements will provide the local ones.


Schematic representation of the GAL project flight. Black dots are GOCE observations (only the first two months have been displayed), red dots are airborne observations.

In the framework of the GAL project GReD has studied and developed versatile software to perform Terrain correction at an altitude in the range between 250 km (GOCE satellite mean altitude) and ground level and downward continuation of the gravitational field.

satellite down

Gravitational signal at different heights: GOCE level, airborne level and ground level.


Moreover GReD had a key role in the scientific organization of the first GAL workshop, held in Como on May 24, 2013.

The project was proposed and carried out by the GAL Consortium, which comprises the following partners:

  1. Galileian Plus srl
  2. Politecnico di Milano, Como Campus
  3. Institut de Geomatica
  4. DEIMOS Engenharia S.A.
  5. Istituto geologico de Catalunya
  6. Ecole Polytechnique Fédérale de Lausanne

GReD supported Politecnico di Milano in the development of new algorithms for precise satellite positioning and for the integration of local gravity models with the global ones derived from the GOCE mission.

The project kick off was on February 15, 2012, and it was completed on February 2014.