Monitoring sea level is critical due to climate change observed over the years. Global Navigation Satellite System Reflectometry (GNSS-R) has been widely demonstrated for coastal sea-level monitoring. The use of signal-to-noise ratio (SNR) observations from ground-based stations has been especially productive for altimetry applications. SNR records an interference pattern whose oscillation frequency allows retrieving the unknown reflector height. Here we report the development and validation of a complete hardware and software system for SNR-based GNSS-R. We make it available as open source based on the Arduino platform. It costs about US$200 (including solar power supply) and requires minimal assembly of commercial off-the-shelf components. As an initial validation towards applications in coastal regions, we have evaluated the system over approximately 1 year by the Guaíba Lake in Brazil. We have compared water-level altimetry retrievals with independent measurements from a co-located radar tide gauge (within 10 m). The GNSS-R device ran practically uninterruptedly, while the reference radar gauge suffered two malfunctioning periods, resulting in gaps lasting for 44 and 38 days. The stability of GNSS-R altimetry results enabled the detection of miscalibration steps (10 cm and 15 cm) inadvertently introduced in the radar gauge after it underwent maintenance. Excluding the radar gaps and its malfunctioning periods (reducing the time series duration from 317 to 147 days), we have found a correlation of 0.989 and RMSE of 2.9 cm in daily means. To foster open science and lower the barriers for entry in SNR-based GNSS-R research and applications, we make a complete bill of materials and build tutorials freely available on the Internet so that interested researchers can  replicate the system.

<p><strong>Abstract.</strong> This paper addresses a historical issue in Brazil that is that topographic mapping has been performed without application of the theories of cartography to local reality. With the lack of research on this subject, the rules and standards for topographic mapping in Brazil are based on solutions that have been developed in other countries. Even though topographic maps are not a frequent topic of cartographic research, as cited by Kent (2009), when the methods, techniques, and standards are imported from other countries, they are established by considering different natural, rural, and urban landscapes; different histories of land use and occupation; and different cultures. Consequently, it is essential to develop studies that address the theoretical issues of topographic mapping and to verify their suitability to Brazilian reality, considering the geographical aspects that must be represented in topographic mapping. Such a foundation of scientific knowledge is essential to producing solutions that are adapted to the environmental conditions and needs of Brazilian users and society.</p>

Between 2013 and 2014, a kinematic positioning based on the Global Navigation Satellite System (GNSS) was carried out for this research work. This GNSS survey resulted in 275916 points with tridimensional coordinates in the cross-border basin area of 58205 km2 called Mirim Lagoon Hydrographic Basin, located in south of Rio Grande do Sul (Brazil) and west of Uruguay. This study aims at showing the methodology firstly and, furthermore, results regarding the validation of the vertical accuracy of the DEM SRTM through kinematic positioning by GNSS, in the Mirim Lagoon Hydrographic Basin region. Also, the GNSS surveying data was post-processed with the Precise Point Positioning (PPP) method, and the ellipsoidal height was converted into orthometric height through the software INTPT geoid. During this study, the geopotential model (EGM96) was used to transform altitude differences between two countries, Brazil and Uruguay. Results showed that the vertical mean absolute error of the DEM SRTM vary from 0.07 m to ± 9.9m with average of -0.28m. This vertical accuracy is better than the absolute vertical accuracy value of ±16m published in the SRTM data specification and validates the DEM SRTM.

Aerodromes protection zones are defined by plans that are determined by three-dimensional (3D) limiting surfaces, which establish the airspace that must remain clear of obstacles, imposing some restrictions on land use. The objective of this paper is to generate 3D models of the surrounding area of Salgado Filho International Airport, considering the constructive altimetric limit established in the Aerodrome Protection Zone Basic Plan (PBZPA), to identify and quantify obstacles related to plots (urban land parcels) and buildings. The adopted methodology includes the analysis and selection of geospatial data, data modeling and performing spatial analysis on the generated 3D models. The results showed that out of a total of 106,838 plots, covering an area of 69.68 km², 4,826 plots (4.52%) exceeded the limiting surface and 1,054 plots (0.99%) represent critical areas where constructions may not be allowed. And, out of a total of 200,573 buildings, 26,418 of them (13.17%) exceeded the limit imposed by PBZPA's. Also, the methodology is valid for detecting and quantifying critical areas concerning the constructive viability of the plots, affected areas regarding the height of the plots and buildings, and for identifying obstacles to aerodromes according to their respective airspace laws.

Este trabalho é parte de uma pesquisa sobre Infraestrutura de Dados Espaciais (IDE). Com o objetivo de evitar a duplicidade de ações e o desperdício de recursos na obtenção de dados geoespaciais, o Governo Brasileiro iniciou, em 2003, estudos sistemáticos com o objetivo de integrar e padronizar os dados espaciais produzidos por diferentes instituições federais. O Decreto 6.666, aprovado em 27 de novembro de 2008, estabeleceu a Infraestrutura Nacional de Dados Espaciais (INDE). A padronização da estrutura de dados espaciais e de metadados proposta pela INDE atende as escalas padrão de 1:25.000, 1:50.000, 1:100.000, 1:250.000 e 1:100.0000 da Cartografia Sistemática Brasileira. O mapeamento topográfico em escalas maiores que 1:25.000, no entanto, ainda carece de uma legislação em âmbito federal para sua normatização. A adoção das normas e padrões propostos pela INDE para projetos cartográficos em escalas grandes significa um avanço nesse sentido e atende à recomendação do Plano de Ação da INDE. Ao considerar a importância dos dados espaciais em escalas grandes para os diferentes setores da sociedade brasileira que utilizam informação espacial, o principal objetivo dessa pesquisa é analisar a aplicabilidade das normas e padrões de dados e de metadados propostos pela INDE, para o mapeamento topográfico em escalas grandes. A metodologia de trabalho adotada compreende o levantamento e a análise das feições mapeadas, a definição da relação destas feições com as categorias, classes, subclasses e atributos de objetos, de acordo com os padrões da INDE, a implementação da base de dados espaciais e a associação dos metadados, para uma área piloto na escala 1:2.000. Os dados utilizados no desenvolvimento deste trabalho referem-se a 123 cartas topográficas na escala 1:2.000. Com os resultados obtidos, verifica-se que as feições representadas em cartas de escalas grandes, como no caso desta pesquisa, podem ser estruturadas de acordo com o modelo de dados e o padrão de metadados propostos na INDE, o que confirma sua aplicabilidade para escalas grandes. Pelo maior grau de detalhamento, inerente à representação de feições na escala 1:2.000, novas classes, novos atributos e novos domínios de atributo foram criados.

No abstract

This paper is on volume visualization of spatial data. It aims at showing new possibilities to visualize three-dimensional phenomena such as geology, soils, geophysics, seismic and the like. The use of volumes in the evaluation processes allows one to visualize and to explore the phenomenon as a continuous body in space, thus incorporating the third dimension in cartography. The volumetric visualization is a branch of scientific visualization that has shown a fast growth and its goal is to comprehend the internal structure and the behavior of three-dimensional volumetric objects. Volumetric visualization depends on the interaction. We must, therefore, interact with the volume trough rotations, cuts and other forms of graphic manipulation, seeking the complete information. The methodology of this research entails the acquisition of three-dimensional data, three-dimensional interpolation, as well as volume formation and visualization by means of three-dimensional Geographic Information System and volumetric visualization software. Soil’s data were interpolated in order to be continuously represented in three-dimensional space. The outcome of volume representations of physical and chemical properties is a new way to visualize the soil and a new source of knowledge to the study of this phenomenon.

Aerodromes protection zones are defined by plans that establish the limits that objects can project into airspace without affecting the safety and regularity of air operations. These plans are composed of a set of imaginary threedimensional surfaces that impose restrictions on the use of properties within the protection zones. Our research problem is how to classify the risk of obstacles in aerodromes protection zones. In this paper, we propose a methodology to obtain an obstacle risk classification model. We defined the risk factors and applied a questionnaire to an expert in civil aviation. The obstacle risk classification model resulted from the specialist analysis and by applying the analytic hierarchy process (AHP) for multi-criteria decision analysis. The advantage of the AHP in studies that use specialists' empiric knowledge for risk modeling is the treatment of uncertainties, and the use of tangibles and intangibles criteria. The results showed that the most significant influence on the risk of an obstacle is how much that obstacle protrudes the limiting surfaces, followed by the distance between the obstacle and the nearest airport runway threshold, the limiting surface in which the obstacle is, and the nature of the obstacle.