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GEOID BEHAVIOUR IN THE BAHIA BLANCA AREA 
Raúl Perdomo y Daniel Del Cogliano 
(Fac. de Cs. Astronómicas y Geofísicas UNLP, CONICET, La Plata, Argentina) 
Nilda Di Croché, Esteban Napal, Beatriz Aldalur, 
Ana María De Aduriz, Pablo Napal, Nora Plana, Irene Pintos 
(Dto. de Ingeniería UNS, Bahía Blanca, Argentina) 
Miguel Angel Martínez (Municipalidad de Bahía Blanca) 
Santiago Rosso (Dirección de Geodesia PBA, Bahía Blanca, Argentina) 
ISPRS Working Group VI/3 
KEYWORDS: Geoid, GPS, Global Models. 
ABSTRACT: 
During November and December 1997 a campaign in the South - South West part of the Buenos Aires 
province was realized. A GPS Network was measured on points of the Argentine Altimétrie and Trigonometric 
Networks. 
With the processing of the campaign data the observed values of N (geodetic undulation) were obtained by 
means of the difference between h (ellipsoidical heights obtained by GPS and referred to the PROSGAR’94 system) 
and H (pre-existing heights referred to the average sea level(geoid)). 
The global model EGM96 was used to obtain the geodetic undulations in this area: these undulations are called 
estimated values of N. 
The difference between the observed values of N and the estimated values of N gives as result a numerical 
model where the differences are bigger in some areas, in the south part specifically, where we consider the possibility of 
making more dense the observations, since it coincides with a complex topography, with heights that reach 700 m 
above the sea level.