The Vertical Reference System in the Argentine Republic

This paper is a summary of the tasks that have been developed and the ones that are under development in the Argentine Republic by means of joint activities, agreements and cooperation among institutions, together with national and international scientific and educational agencies, related to: -Completion, calculation, unification and link to planialtimetric networks. -Gravity activities and procedures used for heights correction. -Linking to neighboring countries networks. -Initial leveling experiences by means of GPS technology, and results obtained. -Regional and national geoid modeling. -Determination of vertical crustal movements, evaluation of sea technology, variations of the mean sea level and its influence over the zero of the argentine height system.Facultad de Ciencias Astronómicas y Geofísica

PROGRAMA CIENTÍFICO PARA O MONITORAMENTO EM TEMPO REAL OU PÓS-PROCESSADO DAS IRREGULARIDADES IONOSFÉRICAS E CINTILAÇÃO DOS SINAIS GNSS

O Brasil é um dos países que mais sofrem os efeitos provocados pela ionosfera, principalmente os oriundos da Anomalia de Ionização Equatorial, irregularidades ionosféricas e cintilação dos sinais GNSS (Global Navigation Satellite System). Várias estratégias podem ser utilizadas para minimizar os efeitos, tais como: modelos ionosféricos, arquivos IONEX ou a combinação linear ion-free. Em se tratando do monitoramento da ionosfera a situação é diferente. A quantidade de instrumentos dedicados ao estudo da camada ionosférica é reduzida no âmbito brasileiro. Neste contexto foi desenvolvido o programa científico denominado Ion_Index, com objetivo de estimar indicadores dos níveis de irregularidades da ionosfera e de cintilação dos sinais GNSS em tempo real ou pós-processado, utilizando a infraestrutura já existente de dados GNSS de redes ativas públicas, como a RBMC, a GNSS-SP e a CALIBRA, transformando assim estações GNSS em estações monitoras da camada ionosférica. Dessa forma é proporcionado um aumento na resolução espacial das informações sobre o comportamento da ionosfera na região brasileira, permitindo um melhor entendimento e contribuindo para o desenvolvimento ou aprimoramento de modelos de mitigação. Experimentos utilizando dados de ionossondas digitais e de receptores PolaRxS-PRO da Septentrio (fontes externas) comprovam a eficiência do program

Optimising the use of GPS multi-reference stations for kinematic positioning

Bibliography: p. 273-293

The Nazca-South America Euler vector and its rate of change

We present velocities relative to the South American plate for five GPS stations on the Nazca plate and use these measurements to estimate the modern Euler vector. We find a pole at 55.8°N, 92.5°W with a rotation rate of 0.60 °/Myr. Because the GPS station at Easter Island appears to be moving at approximately 6.6 mm/yr relative to the other Nazca stations, we repeat our analysis with this station excluded from the inversion to obtain a second and preferred result (called CAP10) with a pole at 61.0°N, 94.4°W and a rate of 0.57 °/Myr. We compare these results with published finite rotation vectors and infer that during the past 10-20 Myrs, the Nazca-South America rotation rate has decelerated by 0.04°-0.06 °/Myr2. © 2003 Elsevier Science Ltd. All rights reserved

Seasonal fluctuations in the mass of the Amazon River system and Earth's elastic response

A GPS station in Manaus, near the center of the Amazon basin, manifests an annual cycle of vertical displacement with a peak-to-peak amplitude of 50-75 mm. This is by far the largest crustal oscillation observed to date, and nearly 2-3 times larger than the amplitude predicted for this region. Vertical ground displacement is strongly anticorrelated with the local stage height of the Amazon river, with no detectable time lag between the two time series. This suggests that we are observing, for the first time, a purely elastic response to changes in the weight of a flowing river system. We use a simple hydrological model to relate stage height to the regional pattern of flooding, and argue that the elastic oscillations observed in Manaus are dominated by changes in water loading developed within ∼200 km of the GPS station. Copyright 2005 by the American Geophysical Union