Marcio Augusto Reolon Schmidt

Gestalt aspects for differentiating the representation of landmarks in virtual navigation

The application of nonimmersive virtual reality (VR) to the creation of rich cartographic representations in 3D is a current research area in cartography. However, the cartographic knowledge needed to build these representations is lacking. The consequences of this include misconceptions in map design that can inhibit or even impair understanding of the representation. A common task in cartographic VR is virtual navigation supported by 3D topographic maps. This geographical task gathers different knowledge schema, based on the selection of specific features for use as landmarks. In VR, there is a need for adaptation of cartographic representations to improve cartographic communication. The strategy adopted in this research uses Gestalt aspects to direct the users selective attention to features that will act as landmarks. To evaluate this proposition, we compare sketch maps from 3D and conventional 2D topographic maps made by 43 volunteers and identify which features were used as landmarks and how they were drawn in the sketch maps. The number of landmarks identified by the user, their topology and orientation, and how the symbols were drawn highlights the success of this proposal for 3D topographic maps for virtual navigation.

PROPOSTA DE USO DAS ÁREAS VARIÁVEIS DE AFLUÊNCIA COMO ÁREA DE PROTEÇÃO PERMANENTE

Despite numerous Brazilian environmental laws, human settlement in protected areas is growing. Among reasons highlight is the management tool of the areas of permanent protection (APP) that define areas symmetrical relative to the center of the water body without, however, consider the physical aspects and dynamics of flow of the river basin. This dynamic is represented by variable source areas (AVA) that define small areas in the watershed and that relate to the quality of water resources, since they are sources of runoff from the saturation and may carry sediments and pollutants for watercourses. As AVA undergo expansion and contraction due to frequency and intensity of precipitation events, in which water saturation occurs, their proper delimitation is not trivial task. Therefore, this article presents a discussion of the definition and modeling of AVA through Geographic Information Systems, with emphasis on its application potential in the delimitation of protected areas in urban environments.

Evaluation of the performance of image classification methods in the identification of vegetation

Orbital imaging techniques offer comprehensive coverage of different regions for numerous environmental and socioeconomic applications, revealing the spatial characteristics and land use of those regions. The advantages of remote sensing include its ability to record spatial distribution patterns, and spectral and temporal data over large regions. The objective of this research is to evaluate the performance of different multispectral image classification methods in the selection of general vegetation, based on a set of samples taken from a LandSat 8 image. The quality of multispectral images and their final classification is usually evaluated based on the Kappa index, which is used as the quality standard in many remote sensing software programs. The classification methods chosen for this study were Parallelepiped, Maximum Likelihood, Mahalanobis Distance, and neural networks. The most suitable classification was used as standard and the other images were compared with it to determine the degree of similarity ranking (IS1x), defined as the percentage of pixels classified differently from those of the standard image. The IS1x was determined using a Matlab routine involving pixel subtraction between images. The results indicate that probability distribution methods are more suitable for discriminating vegetation types than other methods, and that some band combinations should be chosen.

SENSIBILIDADE DE CARACTERÍSTICAS MORFOLÓGICAS NO COMPORTAMENTO DE PARÂMETROS DE QUALIDADE DA ÁGUA EM RIO DE PORTE MÉDIO

Due to the lack of historical water quality data in the country, many technical papers about the river self-cleaning capacity in lotic ambients estimate the biochemical reaction coefficients from empirical equations, which depend on morphological and hydraulic characteristics of the river channel, the quality of the watercourse and the quality of the effluent released in the river. This paper analyzes the sensitivity of some morphological and hydraulic characteristics such as longitudinal slope, cross-section geometry and roughness of the side walls and bottom of the channel, in the concentration change of DO and BOD in a medium-sized river in Minas Gerais Brazil. A reach of 33 km of the Uberabinha River in Triângulo Mineiro has been chosen because its surface water availability and quality are critical for Uberlândia’s water suply system. The simulations showed that (i) the variation of the channel cross-section causes the lowest sensitivity in the OD profile; (ii) the sensitivity in the OD profile is larger for the longitudinal slope and Manning roughness coefficient, which shows the importance of field work and not use of inaccurate techniques for the determination of these two characteristics; (iii) there were not significant BOD differences for the three morphological characteristics analysed. Keywords: Sensitivity analysis, morphological characteristics, self-purification, medium-sized river.

USO DE REDES NEURAIS ARTIFICIAIS NA PONDERAÇÃO INICIAL DA TÉCNICA AHP EM ANÁLISES DE VULNERABILIDADE DE BACIAS HIDROGRÁFICAS

Em muitos problemas decisorios, a informacao fornecida pelos tomadores de decisao muitas vezes e imprecisa ou incerta devido ao limite de tempo, a falta de dados ou capacidades de avaliar as informacoes disponiveis. Como forma de superar essas dificuldades, algumas pesquisas tem apresentado a aplicacao da tecnica Analytical Hierarchic Ponderation (AHP). Esta tecnica estrutura um problema de decisao complicada em uma hierarquia de subproblemas, faz comparacoes par a par das informacoes de entrada e, a partir do ranqueamento dos resultados, permite estimar pesos para cada variavel apresentada. Entretanto, reconhece-se que o ponto mais fraco do metodo e a ponderacao inicial das variaveis de entrada, visto que o conhecimento de especialistas pode ser subjetivo e a importância relativa entre os elementos de analise pode variar. O que nao se discute na literatura e a importância desses pesos e a variacao da ordem no calculo dos pesos finais. Por isso, esta pesquisa avalia diferentes cenarios no contexto de vulnerabilidade ambiental comparando as variacoes entre as ponderacoes iniciais da AHP em relacao a ponderacao realizada por um grupo de especialistas e em relacao a ponderacoes iniciais obtidas a partir de redes neurais como forma de minimizar a subjetividade do processo de analise.

AVALIAÇÃO DA VARIÁVEL VISUAL TAMANHO APLICADA A MAPAS PERSPECTIVOS TRIDIMENSIONAIS

A adocao de um ponto de vista nao ortogonal na construcao dos mapas implica em mudancas no processo construtivo da simbologia para que a comunicacao cartografica seja possivel. Nao existem principios gerais para projetos cartograficos 3D e equivocos no processo de construcao destes mapas podem restringir ou ate mesmo impossibilitar a comunicacao cartografica adequada das feicoes representadas e suas relacoes espaciais. Alem disso, as tecnologias de criacao de imagens permitem solucoes visuais bastante complexas e atrativas, mas o problema de uma simbologia adequada e agravado pela falta de conhecimento de como os usuarios reagem a perspectiva da representacao e as diferencas perceptivas em relacao ao mapa topografico convencional. Por isso existe a necessidade de adaptacao das representacoes cartograficas para o ambiente 3D. Esta pesquisa propoe a avaliacao da variavel tamanho em algumas feicoes especificas em um mapa 3D e avalia a influencia destas na percepcao de usuarios especialistas. Para alcancar este objetivo, a pesquisa apresenta uma metodologia de teste que combina tecnicas qualitativas e quantitativas para mensurar o grau de sucesso da proposicao. Os resultados apontam diferentes graus de percepcao das variaveis visuais no processo de diferenciacao de pontos de referencia.