%0 Conference Proceedings
%@nexthigherunit 8JMKD3MGPCW/43SKC35
%@holdercode {isadg {BR SPINPE} ibi 8JMKD3MGPCW/3DT298S}
%@usergroup administrator
%@usergroup deicy@cptec.inpe.br
%3 10-Alves_et.al_AGU2007_APRESENT.pdf
%B Joint Assembly.
%X Nowadays, the use of Zenithal Tropospheric Delay (ZTD) prediction from Numeric Weather Prediction (NWP) models is a good alternative to minimize the effects of the troposphere in the radio frequency signs for real time and/or pos-processed applications. This process is denominated here after ZTD dynamic modeling. In Brazil, the procedure used to compute the ZTD by the NWP model was jointly developed by researchers from UNESP (São Paulo State University) and CPTEC (Center for Weather Forecasting and Climate Studies) of the INPE (National Institute for Space Research). The ZTD values are provided for all South America twice a day with predictions for a period of 66 hours. The database and the quality analysis are available by CPTEC-INPE in http:satelite.cptec.inpe.br/htmldocs/ztd/zenital.htm. In order to test the performance of the ZTD dynamic modeling in positioning applications, some experiments were carried out. Besides, the results obtained with dynamic modeling were compared with those obtained by Hopfield empirical model. These two tropospheric models were used to generate a VRS (Virtual Reference Station). In the VRS concept developed in this research, a reference station is generated near the user using data provided by a reference network station and atmospheric models. Therefore, the VRS data are not provided by a real receiver. But, the idea is that the VRS data resemble as much as possible a real receiver data at the same location. Therefore, the user has the possibility of using the VRS as if it were a real reference station in your proximities, and to accomplish the relative positioning with a single frequency receiver. This method was implemented in an software which has been developed at UNESP. In order to test the discussed method it was accomplished two experiments using data from two different networks: (a) Brazilian Continuous GPS Network (RBMC) and some extra stations; (b) GPS Active Network of West of São Paulo State. Using the first network it was processed 10 days of data collected in 2005 May. The results obtained by the dynamic modeling were better than those obtained by Hopfield model. It was obtained, on average, an improvement of 19% using the dynamic modeling instead of the Hopfield one. Using the second network it was processed 4 days of data collected in 2006 December. But, in this case, the results obtained were quite similar. This probably happened because in this period occurred a problem with the dynamic modeling. Some data from radiosondes launched over South America were not assimilated during this period deteriorating the ZTD predictions. This fact is important because shows how the assimilation process is important to the ZTD dynamic modeling and revels that this relationship between assimilation data and ZTD prediction quality must be better investigated. But, in spite of this problem, in general the results from dynamic modeling are still good if compared with empirical model.
%@secondarydate 20070522
%T Evaluating the performance of the  CPTEC-INPE/FCT-UNESP troposphere dynamic model using the vrs concept
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress
%@electronicmailaddress lsapucci@cptec.inpe.br
%@format On-line
%@tertiarytype Poster Session
%@secondarytype PRE CI
%K numerical weather prediction, models, atmospheric sciences, zenithal tropospheric, atmosphere monitoring.
%8 22-25 May
%@visibility shown
%@group
%@group
%@group
%@group DMD-INPE-MCT-BR
%@e-mailaddress deicy@cptec.inpe.br
%J Acapulco, México
%@secondarykey INPE-14971-PRE/9883
%@copyholder SID/SCD
%2 sid.inpe.br/mtc-m17@80/2007/10.19.18.37.56
%@affiliation Universidade Estadual Paulista-Faculdade de Ciências e Tecnologia,  Presidente Prudente, SP , Brazil
%@affiliation Universidade Estadual Paulista-Faculdade de Ciências e Tecnologia,  Presidente Prudente, SP , Brazil
%@affiliation Universidade Estadual Paulista-Faculdade de Ciências e Tecnologia,  Presidente Prudente, SP , Brazil
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%I AGU
%4 sid.inpe.br/mtc-m17@80/2007/10.19.18.37
%D 2007
%1 AGU
%S Anais
%A Alves, Daniele Barroca Marra,
%A Dalbelo, Luiz Fernando Antonio,
%A Monico, João  Francisco Galera,
%A Sapucci, Luiz Fernando,
%C Acapulco, México
%@area MET