GENERATION AND PERFORMANCE ANALYSIS OF GPS AND GLONASS VIRTUAL DATA FOR POSITIONING UNDER DIFFERENT IONOSPHERIC CONDITIONS

Several approaches concerning the use in positioning of GNSS (Global Navigation Satellite Systems) can be considered: systems, applied methods and errors that can affect the signals. Following the GLONASS (GLObal NAvigation Satellite System) constellation reestablishment (2011), there was renewed interest in its use with GPS (Global Positioning System). Different possibilities are available concerning applied methods, such as the virtual reference station (VRS) concept (it is possible to obtain data for a virtual station that does not physically exist, using data from a network). One of the main sources of error related to the GNSS signal, is the ionosphere. Many studies have been developed aiming to evaluate GPS positioning quality and influences that can affect it, but there are still several investigation possibilities concerning GLONASS. In this context, this research is intended to assess the GPS/GLONASS virtual data positioning performance considering regions and periods with different ionospheric behavior. A high correlation between the results from virtual and real data (Pearson’s correlation coefficients around 0.8) was noticed. GPS/GLONASS data performance presented better mean squared error results compared to GPS alone (average 3D improvement was 45 cm - 49%). In addition, it was possible to verify ionosphere influence in the positioning error, taking into account station region and period of the year

ASSESSMENT OF GPS/GLONASS POINT POSITIONING IN BRAZILIAN REGIONS WITH DISTINCT IONOSPHERIC BEHAVIOR

Nowadays GPS (Global Positioning System) and GLONASS (GLObal NAvigation Satellite System) are the main systems of GNSS (Global Navigation Satellite Systems), also composed by Galileo and BeiDou. After a long period of degradation, GLONASS was modernized, and its constellation was reestablished in 2011. Considering this new scenario, with GPS and GLONASS full constellations, the interest in the combined use of both systems was renewed. Besides the constellations used, other factors are related to the positioning quality, for instance the ionospheric influence. Several studies have been performed aiming to assess GPS positioning quality as well as the ionospheric influence on it, but concerning GLONASS, there are still several possibilities of investigation. In this context, this research aimed to assess the GPS/GLONASS data point positioning performance considering Brazilian regions with different ionospheric behavior during periods of low and high ionospheric activity. Spatial and time ionospheric influence in the positioning performance were observed. Considering all configurations tested with 30-minute data, the use of GPS/GLONASS data provided better results in 97.35% of the cases when compared to autonomous GPS, the mean improvement was about 60 cm, which corresponds to 30%

Análise do Posicionamento por Ponto Preciso com Dados GPS e GLONASS em Diferentes Latitudes

O GNSS (Global Navigation Satellite System) possui, atualmente, dois sistemas completos, o GPS (Global Positioning System) e o GLONASS (GLObal NAvigation Satellite System). Apesar de terem sido desenvolvidos de forma simultânea, os sistemas apresentam características diferentes. Além disso, o GLONASS passou por um longo período de degradação, o que por muito tempo causou uma lacuna nas investigações realizadas sobre o mesmo. No entanto, em 2011 o GLONASS teve sua constelação restabelecida, renovando o interesse em estudos relacionados ao seu desempenho. No presente trabalho foi investigada a performance dos sistemas GPS e GLONASS de forma autônoma e combinada, considerando estações GNSS em diferentes regiões (latitudes), sendo avaliados os erros obtidos na posição, o número de satélites visíveis e a quantidade de observações coletadas. Em todos os casos considerados, o uso de dados combinados levou a melhores resultados. Em 25% das estações utilizadas o GLONASS apresentou resultados médiosmelhores que o GPS, considerando o posicionamento autônomo

Avaliação do efeito da cintilação ionosférica e de diferentes intervalos de tempo de coleta de dados no posicionamento por ponto preciso na sua forma on-line

O PPP é um método de posicionamento por GNSS que utiliza efemérides precisas, correções dos relógios dos satélites e possíveis modelagens de erros. As possibilidades de aplicações do PPP têm aumentado nos últimos anos, especialmente devido aos serviços on-line, destacando-se entre estes IBGE-PPP, GAPS, APPS e RT_PPP. Esses serviços têm sido utilizados em várias pesquisas e aplicações, porém são poucos os experimentos que consideram ocorrência de cintilação ionosférica. Portanto, no estudo realizado foram selecionados dados de duas estações da RBMC em regiões de alta e baixa atividade ionosférica. Utilizou-se dados de duas épocas do ano, com fraca e forte influência da cintilação ionosfera, buscando-se avaliar o desempenho dos serviços de PPP ­on-line em diferentes intervalos de tempo de coleta de dados GNSS e sob a influência da cintilação ionosférica no posicionamento PPP utilizando o software RT_PPP. Com os dados disponíveis o IBGE-PPP obteve melhores resultados que os demais softwares e o aumento de tempo de coleta de dados melhorou a acurácia do posicionamento. A estação na região sob menor cintilação ionosférica no período de maior atividade ionosférica alcançou resultados mais acurados, entretanto, não se pôde concluir que o motivo foi a cintilação ionosférica

International Nosocomial Infection Control Consortiu (INICC) report, data summary of 43 countries for 2007-2012. Device-associated module

We report the results of an International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2007-December 2012 in 503 intensive care units (ICUs) in Latin America, Asia, Africa, and Europe. During the 6-year study using the Centers for Disease Control and Prevention's (CDC) U.S. National Healthcare Safety Network (NHSN) definitions for device-associated health care–associated infection (DA-HAI), we collected prospective data from 605,310 patients hospitalized in the INICC's ICUs for an aggregate of 3,338,396 days. Although device utilization in the INICC's ICUs was similar to that reported from ICUs in the U.S. in the CDC's NHSN, rates of device-associated nosocomial infection were higher in the ICUs of the INICC hospitals: the pooled rate of central line–associated bloodstream infection in the INICC's ICUs, 4.9 per 1,000 central line days, is nearly 5-fold higher than the 0.9 per 1,000 central line days reported from comparable U.S. ICUs. The overall rate of ventilator-associated pneumonia was also higher (16.8 vs 1.1 per 1,000 ventilator days) as was the rate of catheter-associated urinary tract infection (5.5 vs 1.3 per 1,000 catheter days). Frequencies of resistance of Pseudomonas isolates to amikacin (42.8% vs 10%) and imipenem (42.4% vs 26.1%) and Klebsiella pneumoniae isolates to ceftazidime (71.2% vs 28.8%) and imipenem (19.6% vs 12.8%) were also higher in the INICC's ICUs compared with the ICUs of the CDC's NHSN