A simple visual navigation system for an UAV

We present a simple and robust monocular camera-based navigation system for an autonomous quadcopter. The method does not require any additional infrastructure like radio beacons, artificial landmarks or GPS and can be easily combined with other navigation methods and algorithms. Its computational complexity is independent of the environment size and it works even when sensing only one landmark at a time, allowing its operation in landmark poor environments. We also describe an FPGA based embedded realization of the method’s most computationally demanding phase

A practical multirobot localization system

We present a fast and precise vision-based software intended for multiple robot localization. The core component of the software is a novel and efficient algorithm for black and white pattern detection. The method is robust to variable lighting conditions, achieves sub-pixel precision and its computational complexity is independent of the processed image size. With off-the-shelf computational equipment and low-cost cameras, the core algorithm is able to process hundreds of images per second while tracking hundreds of objects with a millimeter precision. In addition, we present the method's mathematical model, which allows to estimate the expected localization precision, area of coverage, and processing speed from the camera's intrinsic parameters and hardware's processing capacity. The correctness of the presented model and performance of the algorithm in real-world conditions is verified in several experiments. Apart from the method description, we also make its source code public at \emph{http://purl.org/robotics/whycon}; so, it can be used as an enabling technology for various mobile robotic problems

Polarimetric SAR Image Segmentation with B-Splines and a New Statistical Model

We present an approach for polarimetric Synthetic Aperture Radar (SAR) image region boundary detection based on the use of B-Spline active contours and a new model for polarimetric SAR data: the GHP distribution. In order to detect the boundary of a region, initial B-Spline curves are specified, either automatically or manually, and the proposed algorithm uses a deformable contours technique to find the boundary. In doing this, the parameters of the polarimetric GHP model for the data are estimated, in order to find the transition points between the region being segmented and the surrounding area. This is a local algorithm since it works only on the region to be segmented. Results of its performance are presented

SAR image segmentation through B-spline deformable contours and fractal dimension

Synthetic Aperture Radar (SAR) images are usually corrupted by a signal-dependent non-additive noise called speckle. This makes difficult the segmentation, object identification, and feature extraction within this kind of images. In this work we propose the combination of local fractal estimation and B-Spline based active contours as a solution for the boundary extraction problem in SAR images. After a supervised initialization (the specification of a an initial curve laying completely within the region of interest), the algorithm searches the control points (vertices) of a B-Spline curve that fits the boundary of the region to be segmented. The vertices of the curve are found by a local estimation of the fractal dimension in the surrounding. Fractal dimension provides a good local roughens and statistical correlation estimation. Box-counting measurement of the fractal dimension is widely acknowledged to be the most adequate in terms of robustness and computational requirements. Box counting algorithms are based on a statistical analysis of the brightness distribution of the pixels in a surrounding of varying sizes. A power law can be established between the surrounding size and the amount of pixels with a given brightness profile, and then an adequate assessment of the local fractal dimension can be performed. The proposed algorithm is systematically tested on synthetic and real SAR images, and both the accuracy and the performance of our proposal are assessed.

Inscrições de si: da porta de banheiro ao chat

Writing pervades human history, from rupestrian inscriptions to internet. Although supports change – walls, papyrus, parchments, tiles, papers, computer monitors – there remains a register, which transports human being beyond its own existence and which, precisely, renders it existing. In this thesis, I argue that restroom graffiti, apocryphal and ephemeral by their nature, are a link of the chain that identifies human being as the one who is capable of writing. It is an entity that can be figured out through its marks. Without aiming to interpret inscriptions, I restrict myself to observing that a great amount of impressions prefer to be revealed on the subversive support of the cell defined by the restroom door. And that the freedom of being anonymous that characterizes that door is kept when its contents are transposed to internet chatsSubmitted by Rogele Pinheiro ([email protected]) on 2018-01-17T16:36:01Z No. of bitstreams: 1 79337_Dagoberto.pdf: 1658018 bytes, checksum: 52d6a5632b5504995da34b4ef506d1d8 (MD5)Approved for entry into archive by Gheovana Figueiredo ([email protected]) on 2018-01-17T17:12:37Z (GMT) No. of bitstreams: 1 79337_Dagoberto.pdf: 1658018 bytes, checksum: 52d6a5632b5504995da34b4ef506d1d8 (MD5)Made available in DSpace on 2018-01-17T17:12:37Z (GMT). No. of bitstreams: 1 79337_Dagoberto.pdf: 1658018 bytes, checksum: 52d6a5632b5504995da34b4ef506d1d8 (MD5) Previous issue date: 2005A escrita permeia a história da humanidade desde as inscrições rupestres até a internet. Embora mudem os suportes – paredes, papiros, pergaminhos, cerâmica, papel, o monitor de um computador –, permanece um registro que transporta o ser humano para além de sua própria existência e que, justamente, faz com que passe a existir. Defendo a idéia, nesta dissertação, de que os grafitos de porta de banheiro, apócrifos e efêmeros por natureza, são elo na corrente que identifica o ser humano como ser que é capaz de escrever. Ele é uma entidade que pode ser descoberta por suas marcas. Sem buscar interpretar as inscrições, atenho-me a observar que uma extensa quantidade de impressões prefere ser revelada no suporte subversivo da célula que a porta de banheiro encerra. E que a liberdade desta mesma porta de aparecer anônima se mantém quando seus conteúdos são transportados para a internet, para as salas de bate-papo

Supervised biometric system using multimodal compression scheme

International audienceThis work is a part of a project supported by STIC Am-Sud where the main objective is to design an intelligent vision system to protect children from some critical information accessible from the Internet, from some videos or from some video games that are related to violence, wars, pornography, etc. Considered definitively not appropriate for their age, such multimedia contains can significantly offend young people. More specifically, in this paper, we are interested in discussing a general concept of a supervised biometric system that is controlled by specific tags embedded in video frames through a multimodal compression. Using a spiral insertion scheme, specific frequencies (TAGs) are compressed jointly with video frames in the region of insertion and then extracted for supervision purpose. The multimodal compression is considered here because it allows high-level robustness regarding the bitrates and down-sampling