Abstract. In prevalent engineering practice, geodetic measurement techniques are commonly applied for structural monitoring. For a long time, triangulation, trilateration and levelling techniques have been trusted for the determination of structural deformation and point displacement, with excellent outcomes. With the advent of robotic total stations, the three-dimensional topographic measurement method has been proposed as an efficient and rapid measurement option for the determination of 3D coordinates. In addition, the GNSS (Global Navigation Satellite System) technology improvements, mainly in the RTK (Real-Time Kinematic) measurement mode, opened a new perspective for monitoring, which has also shown consistent results. However, there are some situations where the use of total station or GNSS technology individually is not enough to perform the monitoring. The solution may then be the combination of both technologies. In this paper, we present the details of two proposed measurement methods and the results of a testing campaign carried out to monitor the construction of "La Costanera Tower", in Santiago, Chile, using a total station combined with GNSS receivers. These methods are based on the use of GNSS antennas and total station installed on the under-construction building floor. Having this scenario, two measurement procedures were applied. The first one was based on using a total station coupled with a GNSS receiver, for determining the position of the monitoring point and a GNSS antenna coupled with prism reflector, for the orientation of the total station. The second procedure was based on using a total station and two GNSS antennas coupled with prism reflectors. With this equipment, directions and distances were measured, to determine the position and orientation of the total station, by means of a Free Station positioning computation. The testing results have been compared with traditional measurement techniques. The results showed that the proposed methods could be a suitable solution for monitoring tall building construction.
This paper presents a comparative study of the displacement of the Brazilian Funil Shell Dam centre arch crown as derived from two measurement campaigns using three independent procedures: GPS satellite positioning, terrestrial geodetic techniques and coupled optical plumb measurements with an inverted pendulum. For the GPS measurement, four dual frequency GX1220 GPS receivers from Leica Geosystems were installed in the crest of the dam and in three concrete pillars used as control points. For geodetic measurement, a DI2002 Electronic Distancemeter fitted on the telescope of a T2 theodolite was used. The optical plumb measurement was made using a Nadiral Optical Plumb manufactured by Wild Heerbrugg and calibrated by Furnas Metrology Laboratory. Results showed that GPS technology can be used successfully for horizontal displacement monitoring in areas with high level of multi-path such as water dam surrounding area. The GPS accuracy was also estimated based on the Gauss-Markov homoscedastic model using the historical nadiral optical plumb observations as standard observation.
Uma característica inerente aos bancos de dados de acidentes rodoviários refere-se ao desequilíbrio existente entre o número de observações associadas às ocorrências dos acidentes com vítimas fatais e não fatais, em relação aos acidentes sem vítimas. Essa particularidade conduz à necessidade da aplicação de técnicas de balanceamento, que possibilitam a reamostragem de classes e atributos. Assim, assegura-se que não haja um super ajuste dos dados em problemas de classificação. Este trabalho investigou a influência de diferentes métodos de balanceamento como undersampling, oversampling e SMOTE no processo de classificação da severidade de acidentes rodoviários pela abordagem de Redes Neurais Artificiais. Os resultados obtidos indicam que o balanceamento proporciona um ganho significativo na taxa de acerto da classificação das classes minoritárias. Verifica-se um melhor ajuste do classificador ao modelo e o ganho na qualidade e acurácia do processo de classificação, principalmente, quando são utilizadas técnicas de sobre amostragem como a SMOTE.
The present study aims to evaluate the TOPODATA Digital Elevation Model (DEM) as a source of relevant altimetric information for urban cycling planning. A case study was conducted in the city of Bariri-SP. The Cartographic Accuracy Standard of Digital Cartographic Products (PEC-PCD), assessed by comparing the TOPODATA altitudes with homologous altitudes surveyed by a precise satellite method (GNSS), suggests that the DEM may not be adequate for phases of cycling planning that require greater detailing of the elements to be designed. A moderate to strong positive spatial autocorrelation was observed between the DEM errors. Regarding its usability for estimating the average slopes of the road segments, however, the results suggest that TOPODATA average slopes do not differ statistically from those estimated with field-surveyed data and, for the two criteria adopted for acceptable gradient lengths for cycling, more than 82% of the road segments were classified similarly using both sources of information.
Direito autoral: Este artigo está licenciado sob os termos da Licença Creative Commons-Atribuição 4.0 Internacional.
O objetivo deste estudo foi discutir as principais limitações encontradas no processo de classificação da severidade dos acidentes de tráfego, com base em modelos de árvore de decisão (CART). Para atingir este objetivo, a CART foi utilizada na mineração de um banco de dados desbalanceado de acidentes rodoviários, considerando a variável dependente severidade da lesão, a qual foi categorizada em acidentes sem vítimas e com vítimas (fatais e não fatais). Para tanto, foram utilizadas as variáveis associadas às características dos acidentes, à infraestrutura viária e às condições ambientais, com a finalidade de se identificar a influência desses fatores na variação da severidade dos acidentes. Embora a classificação pela CART tenha resultado em uma alta acurácia, a mesma forneceu baixa taxa de acerto na classificação dos acidentes com vítimas, que correspondem às observações mais raras do banco de dados. Além disso, resultou na extração de um elevado número de regras de decisão, considerando o número de categorias das variáveis independentes no processo de predição da variável alvo. Os resultados indicaram que a CART não é eficiente no estudo de efeitos multicausais como os acidentes rodoviários, pois não tem a potencialidade de associação de um vasto número de parâmetros, o que restringe a análise e interpretação dos resultados quanto à estrutura binária da árvore. Ela é indicada, no entanto, para a análise exploratória de bancos de dados, quando se deseja analisar a influência de uma categoria específica de uma variável do banco de dados na ocorrência dos acidentes de tráfego.
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