IGeS International Geoid Service

In the last two years, IGeS activities have been mainly focussed on:
– a test on quasi-geoid computation methods, the Auvergne test;
– the participation to the validation of the EGM2008 global geopotential model;
– the organization of schools on geoid computation;
– the support given in computing high definition geoid in South India and Bangladesh.
The Auvergne test on quasi-geoid estimation has been set up in co-operation with IGN and EGGP. IGN supplied the gravity, DTM and GPS/levelling data while EGGP contributed in assessing the test procedures. A first comparison between the computations performed by six different groups have been presented during the last Hotine-Marussi Symposium held in Rome (July 5th-9th, 2009).
The results of this test proved the substantial equivalence of the applied computation methods.
The validation of the EGM2008 global geopotential model has been performed in the frame-work of the activities of the Joint Working Group (JWG) between the International Gravity Field Service (IGFS) and the Commission 2 of the International Association of Geodesy (IAG), entitled “Evaluation of Global Earth Gravity Models”. IGeS participated to the test on EGM2008 comparing it with data covering two areas: the Central Mediterranean area and the South of India.
The scientific papers on EGM2008 validation have been collected in a special issue of the Newton’s Bulletin (the Bulletin n° 4) which can be downloaded at the IGeS web page. This special issue of Newton’s Bulletin consists of 25 peer-reviewed evaluation papers of EGM2008 (and partially of PGM2007A), which are grouped into four different sections according to the geographical region of the evaluation tests: Global, the Americas, Europe and Africa, and Asia, Australia and Antarctica. Their results provide a thorough external assessment of EGM2008, using a variety of geodetic data and testing methodologies.
As it is usually done since 1999, schools on geoid computation have been organized by IGeS in the last two years. A school have been held in Como, in September 15th-19th, 2008.
Also, new schools have been planned in the near future. The next school is going to be held in Universidad National de la Plata, Fac. de Ciencias Astronómicas y Geofísicas , La Plata, Argentina, on September 7th-11th , 2009. A second forthcoming school is going to be organized in Saint Petersburg, in 2010.
Finally, IGeS gave support to researchers in computing local geoids. This has been done in the last two years period in two different areas of the world, namely South India and Bangladesh.
The National Geophysical Research Institute of Hyderabad (India) contacted IGeS in order to get support in computing a gravimetric geoid in South India. This has been done mainly for geophysical investigation in this area, even though the quality of the estimated geoid allows its use also in height conversions (e.g. from ellipsoidal to orthometric heights). Report of the International Association of Geodesy 2007-2009 - Travaux de l’Association Internationale de Géodésie 2007-2009 A co-operation was also established with the Survey of Bangladesh. A researcher of the Survey of Bangladesh was hosted at IGeS in Milano, in February, 2009. During this period, a refinement of the EGM2008 over Bangladesh was computed, based on GPS/levelling points which were collected by the Survey of Bangladesh. This refinement proved to be effective and led to a significant improvement of the global EGM2008 model.