A low-cost 3D reconstruction system using a single-shot projection of a pattern matrix

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação do potencial das imagens quickbird ortorretificadas para o mapeamento das propriedades localizadas na área de expansão e vazios urbanos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Extração de feições retas com precisão subpixel: estudo comparativo entre três métodos

In the fields of Machine Vision and Photogrammetry, extracted straight lines from digital images can be used either as vector elements of a digital representation or as control entities that allow the determination of the camera interior and exterior orientation parameters. Applications related with image orientation require feature extraction with subpixel precision, to guarantee the reliability of the estimated parameters. This paper presents three approaches for straight line extraction with subpixel precision. The first approach considers the subpixel refinement based on the weighted average of subpixel positions calculated on the direction perpendicular to the segmented straight line. In the second approach, a parabolic function is adjusted to the grey level profile of neighboring pixels in a perpendicular direction to the segmented line, followed by an interpolation of this model to estimate subpixel coordinates of the line center. In the third approach, the subpixel refinement is performed with a parabolic surface adjustment to the grey level values of neighboring pixels around the segmented line. The intersection of this surface with a normal plane to the line direction generates a parabolic equation that allows estimating the subpixel coordinates of the point in the straight line, assuming that this is the critical point of this function. Three experiments with real images were made and the approach based on parabolic surface adjustment has presented better results.

Fototriangulação com parâmetros adicionais para câmaras digitais: uma avaliação experimental

Considering the growing use of digital cameras in Photogrammetric projects, especially in aerial survey, this paper presents tests and analyses of bundle block adjustment with additional parameters, using different mathematical models, and blocks of images acquired by the SAAPI digital acquisition system. Three blocks of images were processed by the LPS (Leica Photogrammetry Suite) software, in which five groups of additional parameters (AP) can be used: Bauer, Jacobsen, Ebner, Brown and Lens distortion. These AP's models were employed in the bundle block adjustment, and the results were analyzed based on the accuracy of the checking points and on the changes in these additional parameters. The obtained results showed that the Lens Distortion model allowed the best results.

Extração automatica de segmentos lineares de rodovias em imagens de resoluções variadas

In this paper a methodology for automatic extraction of road segments from images with different resolutions (low, middle and high resolution) is presented. It is based on a generalized concept of lines in digital images, by which lines can be described by the centerlines of two parallel edges. In the specific case of low resolution images, where roads are manifested as entities of 1 or 2 pixels wide, the proposed methodology combines an automatic image enhancement operation with the following strategies: automatic selection of the hysteresis thresholds and the Gaussian scale factor; line length thresholding; and polygonization. In medium and high resolution images roads manifest as narrow and elongated ribbons and, consequently, the extraction goal becomes the road centerlines. In this case, it is not necessary to apply the previous enhancement step used to enhance roads in low resolution images. The results obtained in the experimental evaluation satisfied all criteria established for the efficient extraction of road segments from different resolution images, providing satisfactory results in a completely automatic way.

A influência das injunções de orientação relativa na calibração de um sistema dual de câmeras digitais

Image acquisition systems based on multi-head arrangement of digital frame cameras, such as the commercial systems DMC, UltraCam, besides others, are attractive alternatives enabling larger imaging area when compared to a single frame camera. Considering that in these systems, cameras are tightly attached to an external mount, it is assumed that relative position and orientation between cameras are stable during image acquisition and, consequently, these constraint can be included in the calibration step. This constraint is acceptable because estimates of the relative orientation (RO) parameters between cameras, from previously estimated exterior orientation parameters, present higher and significant deviations than the expected physical variations, due to error propagation. In order to solve this problem, this work presents an approach based on simultaneous calibration of two or more cameras using constraints that state that the relative rotation matrix and the distance between the cameras head are stable. Experiments with images acquired by an arrangement of two Hasselblad H2D cameras were accomplished, without and with the mentioned constraints. The experiments showed that the calibration process with RO constraints allows better results than the approach based on single camera calibration, provided that the estimation has included only images with good target distribution.

Orientação indireta de imagens com uso de apoio fotogramétrico extraído a partir da integração de dados derivados do sistema lidar e fotogrametria

In this work a method is proposed to allow the indirect orientation of images using photogrammetric control extracted through integration of data derived from Photogrammetry and Light Detection and Ranging (LiDAR) system. The photogrammetric control is obtained by using an inverse photogrammetric model, which allows the projection of image space straight lines onto the object space. This mathematical model is developed based on the intersection between the collinearity-based straight line and a DSM of region, derived from LiDAR data. The mathematical model used in the indirect orientation of the image is known as the model of equivalent t planes. This mathematical model is based on the equivalence between the vector normal to the projection plane in the image space and to the vector normal to the rotated projection plane in the object space. The goal of this work is to verify the quality, efficiency and potential of photogrammetric control straight lines obtained with proposed method applied to the indirect orientation of images. The quality of generated photogrammetric control was statistically available and the results showed that proposed method is promising and it has potential for the indirect orientation of images.

Avaliação postural em pacientes com doença pulmonar obstrutiva crônica

O objetivo deste estudo foi avaliar alterações posturais em pacientes com Doença Pulmonar Obstrutiva Crônica (DPOC), por meio do Software para Avaliação Postural (SAPO). Trinta indivíduos constituíram 2 grupos: 15 pacientes com DPOC e 15 idosos saudáveis (controle). Os grupos realizaram espirometria e foram fotografados para avaliação postural. As imagens obtidas foram digitalizadas e, posteriormente, avaliou-se dez alterações posturais com o SAPO [inclinação lateral da cabeça (ILC), desnivelamento dos ombros (DO), desnivelamento pélvico anterior (DPA), inclinação lateral do tronco (ILT), desnivelamento das escápulas (DE), desnivelamento pélvico posterior (DPP), protusão da cabeça (PC), protusão de ombro (PO), báscula anterior da pelve (BAP) e cifose torácica (CT)]. Essas alterações, obtidas no grupo controle, foram conferidas com o padrão de normalidade para adultos jovens, proposto em estudo prévio. Para a comparação das alterações posturais entre grupo controle e DPOC, foi utilizado o teste de Mann-Whitney em grupo controle, e em adultos jovens, o teste t de Student não pareado, ambos com nível de significância estatística de 5%. Dentre as dez alterações posturais, o grupo controle apresentou sete (ILC, DPA, DE, DPP, PC, PO, BAP) com valores angulares significativamente maiores em relação aos adultos jovens. Quando comparados a idosos saudáveis, indivíduos com DPOC apresentaram um aumento significante na angulação de BAP, DPP e CT. Pacientes com DPOC apresentam três alterações posturais que provavelmente estão relacionadas à doença.

Análise do alinhamento dos membros inferiores em crianças com excesso de peso

O sobrepeso e a obesidade (SO) têm atingido proporções epidêmicas, principalmente, em idade escolar, tornando-se um problema mundial de saúde. Muitas adaptações podem ocorrer na organização postural de crianças com SO, provocando, graves consequências. A avaliação postural pode colaborar para o entendimento destas alterações. O objetivo do presente estudo foi verificar alterações na postura dos membros inferiores de crianças com SO, através de metodologia específica. Vinte e dois indivíduos, sendo distribuídos de acordo com o sexo: 9 do feminino e 13 do masculino, com faixa etária entre 5-9 anos, participaram do estudo. Na avaliação postural, foram utilizados a fotogrametria e o software SAPo. Foram analisados os ângulos articulares dos membros inferiores e a projeção plantar do centro de gravidade. Foi utilizada estatística não-paramétrica descritiva, além dos testes de Kruskal-Wallis e de Mann-Whitney (p<0,05), para comparação entre os sexos. Ambos os sexos apresentaram anteroversão e leve rotação pélvica, à direita para o feminino e à esquerda para o masculino hiperextensão e valgismo de joelhos e valgismo tornozelos. O centro de gravidade apresentou 26,95% de anteriorização. Conclui-se que a avaliação postural nessa população foi congruente aos achados da literatura e a metodologia utilizada possibilitou quantificar os dados para futuras comparações.

Confiabilidade inter e intraexaminadores nas mensurações angulares por fotogrametria digital e goniometria

INTRODUÇÃO: A utilização da fotogrametria computadorizada em prol da goniometria, ou vice-versa, na prática clínica ainda necessita de fundamentações consistentes. OBJETIVOS: Os objetivos deste estudo foram: verificar a confiabilidade inter e intraexaminadores avaliadores na quantificação das medidas angulares obtidas a partir da fotogrametria computadorizada e a goniometria e determinar a confiabilidade paralela entre esses dois diferentes instrumentos de avaliação. MATERIAIS E MÉTODOS: 26 voluntários e 4 examinadores foram utilizados no estudo. A coleta foi realizada em 4 etapas sequenciais: demarcação dos pontos anatômicos de referência, mensuração e registro dos valores goniométricos, captação da imagem do voluntário com os marcadores fixados no corpo e avaliação do registro fotográfico no programa ImageJ. RESULTADOS: O goniômetro é um instrumento confiável na maioria das evidências, porém, a confiabilidade das medições depende principalmente da uniformização dos procedimentos. Considerações metodológicas relativas ao estabelecimento de confiabilidade e padronização da colocação dos marcadores se fazem necessárias, de modo a oferecer opções de avaliação ainda mais confiáveis para a prática clínica. CONCLUSÃO: Ambos os instrumentos são confiáveis e aceitáveis, porém, mais evidências ainda são necessárias para suportar a utilização desses instrumentos, pois poucos pesquisadores têm utilizado o mesmo desenho de estudo, e a comparação dos resultados entre eles muitas vezes são difíceis.

Automatic absolute orientation of scanned aerial photographs

Image orientation is a basic problem in Digital Photogrammetry. While interior and relative orientations were succesfully automated, the same can not be said about absolute orientation. This process can be automated by using an approach based on relational matching and a heuristic that uses the analytical relation between straight features in the object space and its homologous in the image space. A build-in self-diagnosis is also used in this method, that is based on the implementation of data snooping statistic test in the process of spatial resection, using the Iterated Extended Kalman Filtering (IEKF). The aim of this paper is to present the basic principles of the proposed approach and results based on real data.

Strategy to detect ground control in digital images

The identification of ground control on photographs or images is usually carried out by a human operator, who uses his natural skills to make interpretations. In Digital Photogrammetry, which uses techniques of digital image processing extraction of ground control can be automated by using an approach based on relational matching and a heuristic that uses the analytical relation between straight features of object space and its homologous in the image space. A build-in self-diagnosis is also used in this method. It is based on implementation of data snooping statistic test in the process of spatial resection using the Iterated Extended Kalman Filtering (IEKF). The aim of this paper is to present the basic principles of the proposed approach and results based on real data.

Accuracy assessment of a photogrammetric close-range reconstruction system

Geometric accuracy of a close-range photogrammetric system is assessed in this paper considering surface reconstruction with structured light as its main purpose. The system is based on an off-the-shelf digital camera and a pattern projector. The mathematical model for reconstruction is based on the parametric equation of the projected straight line combined with collinearity equations. A sequential approach for system calibration was developed and is presented. Results obtained from real data are also presented and discussed. Experiments with real data using a prototype have indicated 0.5mm of accuracy in height determination and 0.2mm in the XY plane considering an application where the object was 1630mm distant from the camera.