Leveraging feature uncertainty in the PnP problem

Trabajo presentado a la 25th British Machine Vision Conference (BMVC), celebrada en Nottingham (UK) del 1 al 5 de septiembre de 2014.-- Este ítem (excepto textos e imágenes no creados por el autor) está sujeto a una licencia de Creative Commons: Attribution-NonCommercial-NoDerivs 3.0 Spain.We propose a real-time and accurate solution to the Perspective-n-Point (PnP) problem --estimating the pose of a calibrated camera from n 3D-to-2D point correspondences-- that exploits the fact that in practice the 2D position of not all 2D features is estimated with the same accuracy. Assuming a model of such feature uncertainties is known in advance, we reformulate the PnP problem as a maximum likelihood minimization approximated by an unconstrained Sampson error function, which naturally penalizes the most noisy correspondences. The advantages of this approach are clearly demonstrated in synthetic experiments where feature uncertainties are exactly known. Pre-estimating the features uncertainties in real experiments is, though, not easy. In this paper we model feature uncertainty as 2D Gaussian distributions representing the sensitivity of the 2D feature detectors to different camera viewpoints. When using these noise models with our PnP formulation we still obtain promising pose estimation results that outperform the most recent approaches.This work has been partially funded by Spanish government under projects DPI2011-27510, IPT-2012-0630-020000, IPT-2011-1015-430000 and CICYT grant TIN2012-39203; by the EU project ARCAS FP7-ICT-2011-28761; and by the ERA-Net Chistera project ViSen PCIN-2013-047.Peer Reviewe

Very fast solution to the PnP problem with algebraic outlier rejection

Presentado al CVPR 2014 celebrado en Columbus, Ohio (US) del 23 al 28 de junio.We propose a real-time, robust to outliers and accurate solution to the Perspective-n-Point (PnP) problem. The main advantages of our solution are twofold: first, it integrates the outlier rejection within the pose estimation pipeline with a negligible computational overhead; and second, its scalability to arbitrarily large number of correspondences. Given a set of 3D-to-2D matches, we formulate pose estimation problem as a low-rank homogeneous system where the solution lies on its 1D null space. Outlier correspondences are those rows of the linear system which perturb the null space and are progressively detected by projecting them on an iteratively estimated solution of the null space. Since our outlier removal process is based on an algebraic criterion which does not require computing the full-pose and reprojecting back all 3D points on the image plane at each step, we achieve speed gains of more than 100× compared to RANSAC strategies. An extensive experimental evaluation will show that our solution yields accurate results in situations with up to 50% of outliers, and can process more than 1000 correspondences in less than 5ms.This work has been partially funded by Spanish government under projects DPI2011-27510, IPT-2012-0630-020000, IPT-2011-1015-430000 and CICYT grant TIN2012-39203; by the EU project ARCAS FP7-ICT-2011-28761; and by the ERA-Net Chistera project ViSen PCIN-2013-047Peer Reviewe

Extradural hematoma: comparative radiological study between, comatous and noncomatous patients

A series of 129 patients harbouring extradural hematomas was analysed considering the neurological state immediately before operation as the most consistent variable. Seventy eight patients were considered to be comatous (Group I) and 51 were noncomatous. Among the comatous group, 30 were investigated with computerized tomography (23.3% mortality, 50% good results), 31 were submitted to angiography (48.3% mortality, 38.7% good results), and 17 were operated based on the neurological examination and skull radiography (47% mortality, 35.2% good results). The presence or absence of skull fracture and the density of hematoma did not change the final outcome. Associated intracranial lesions increased the mortality and lowered the good results in both groups. Frontal hematomas (10 cases) in the comatous group were associated with high mortality (52.6%) due to bad neurological state (Glasgow 3-5) and to isolated or multiple intracranial associated lesions (6 patients).Considerando o estado neurológico imediatamente antes da operação como a variável miais fidedigna para antecipação do prognóstico dos hematomas extradurais, os autores realizaram estudo radiológico comparativo de 129 pacientes operados por esta patologia. Desta amostra, 78 casos se encontravam em coma (Grupo I) e 51 eram não comatosos (Grupo II). No grupo I, os 30 casos investigados pré-operatoriamente com tomografia tiveram 23,3% de mortalidade e 50% de bons resultados; dos 31 casos submetidos a angiografia, 48,3% faleceram e 38,7% tiveram bons resultados; 17 casos foram operados pela radiografia simples de crânio e exame neurológico, com 47% de mortalidade e 35,2% de bons resultados. A presença de fratura de crânio e a densidade tomográfica do hematoma não interferiram nos resultados. A presença de lesão associada intracraniana aumentou a mortalidade e diminuiu a quantidade de bons resultados tanto no Grupo I quanto no Grupo II. A localização frontal do hematoma foi associada a elevada mortalidade (52,6%) no grupo comatoso, por estarem todos os pacientes entre 3 a 5 pontos na Escala de Glasgow e seis deles por apresentarem lesões associadas intracranianas únicas ou múltiplas.Hospital Santa IsabelEscola Paulista de MedicinaUNIFESP, EPMSciEL

Pasture digital image analysis as a support tool for grazing management in montados: a preliminary approach

The knowledge of vegetation land cover over time is essential for an appropriate grazing management in any free range animal production system. Ground vegetation has traditionally been monitored using visual methods that produce estimates of percentage covered/bared soil, green/senescent vegetation and also grasses/forbs occurrences. Visual methods are extremely time consuming and prone to observer bias. The use of digital image to evaluate and monitor ground vegetation has increased in recent years. These techniques allow a more cost effective data collection over larger areas, avoiding the need of judgement-based choices of representative areas. The aim of this work is to test the applicability and robustness of simple image processing techniques to monitor ground vegetation in Montado. The set of images were collected using a GoPro HD HERO2 digital camera, facing down, mounted on a stand at constant distance above ground.An application of threshold segmentation techniques to a set of digital images is presented. A procedure to calibrate the threshold value is proposed. Some results are presented and analyzed for different lighting conditions, type of vegetation, as well as percentage of Montado vegetation cover. Montados are characterized by a pronounced patchiness of vegetation communities and should benefit from such an approach

An assessment for UAS depart and approach operations

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation. In previous research advances have been proposed in the flight plan capabilities by offering semantically much richer constructs than those present in most current UAS autopilots. The introduced flight plan is organized as a set of stages, each one corresponding to a different flight phase. Each stage contains a structured collection of legs inspired by current practices in Area Navigation (RNAV). However, the most critical parts of any flight, the depart and approach operations in an integrated airspace remain mostly unexplored. This paper introduces an assessment of both operations for UAS operating in VFR and IFR modes. Problems and potential solutions are proposed, as well as an automating strategy that should greatly reduce pilot workload. Although the Document type: Conference objec

Uncertainty-aware camera pose estimation from points and lines

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Perspective-n-Point-and-Line (PnPL) algorithms aim at fast, accurate, and robust camera localization with respect to a 3D model from 2D-3D feature correspondences, being a major part of modern robotic and AR/VR systems. Current point-based pose estimation methods use only 2D feature detection uncertainties, and the line-based methods do not take uncertainties into account. In our setup, both 3D coordinates and 2D projections of the features are considered uncertain. We propose PnP(L) solvers based on EPnP and DLS for the uncertainty-aware pose estimation. We also modify motion-only bundle adjustment to take 3D uncertainties into account. We perform exhaustive synthetic and real experiments on two different visual odometry datasets. The new PnP(L) methods outperform the state-of-the-art on real data in isolation, showing an increase in mean translation accuracy by 18% on a representative subset of KITTI, while the new uncertain refinement improves pose accuracy for most of the solvers, e.g. decreasing mean translation error for the EPnP by 16% compared to the standard refinement on the same dataset.This work has been partially funded by the Spanish government under projects HuMoUR TIN2017-90086-R, ERA-Net Chistera project IPALM PCI2019-103386 and María de Maeztu Seal of Excellence MDM-2016-0656Peer ReviewedPostprint (author's final draft

Epidemiology of fungal infections in liver transplant recipients: a six-year study of a large Brazilian liver transplantation centre

Liver transplant seems to be an effective option to prolong survival in patients with end-stage liver disease, although it still can be followed by serious complications. Invasive fungal infections (ifi) are related to high rates of morbidity and mortality. The epidemiology of fungal infections in Brazilian liver transplant recipients is unknown. The aim of this observational and retrospective study was to determine the incidence and epidemiology of fungal infections in all patients who underwent liver transplantation at Albert Einstein Israeli Hospital between 2002-2007. A total of 596 liver transplants were performed in 540 patients. Overall, 77 fungal infections occurred in 68 (13%) patients. Among the 77 fungal infections, there were 40 IFI that occurred in 37 patients (7%). Candida and Aspergillus species were the most common etiologic agents. Candida species accounted for 82% of all fungal infections and for 67% of all IFI, while Aspergillus species accounted for 9% of all fungal infections and for 17% of all IFI. Non-albicans Candida species were the predominant Candida isolates. Invasive aspergillosis tended to occur earlier in the post-transplant period. These findings can contribute to improve antifungal prophylaxis and therapy practices in Brazilian centres.Universidade Federal de São Paulo (UNIFESP)Hospital Israelita Albert EinsteinUNIFESPSciEL

Incidental Diagnosis of Bladder Cancer in a 17-year-old Patient

AbstractBladder cancer is the fourth most common type of cancer among males and the ninth most common cause of cancer death. Bladder cancer can occur at any age. This paper reports the incidental diagnosis of bladder cancer in a 17-year-old female patient. Data on bladder cancer at this age are uncommon in the literature