Extrinsic Auto-calibration of a Camera and Laser Range Finder

This paper describes theoretical and experimental results for the auto-calibration of sensor platform consisting of a camera and a laser range finder. Real-world use of autonomous sensor platforms often requires the recalibration of sensors without an explicit calibration object. The constraints are based upon data captured simultaneously from the camera and the laser range finder while the sensor plat-form undergoes an arbitrary motion. The rigid motions of both sensors are related, so these data constrain the relative position and orientation of the camera and laser range finder. We introduce the mathematical constraints for auto-calibration techniques based upon both discrete and differential motions, and present simulated experimental results, and results from a implementation on a B21rT M Mobile Robot from iRobot Corporation. This framework could also encompass extrinsic calibration with GPS, inertial, infrared, and ultrasonic sensors

Autocalibrating vision guided navigation of unmanned air vehicles via tactical monocular cameras in GPS denied environments

This thesis presents a novel robotic navigation strategy by using a conventional tactical monocular camera, proving the feasibility of using a monocular camera as the sole proximity sensing, object avoidance, mapping, and path-planning mechanism to fly and navigate small to medium scale unmanned rotary-wing aircraft in an autonomous manner. The range measurement strategy is scalable, self-calibrating, indoor-outdoor capable, and has been biologically inspired by the key adaptive mechanisms for depth perception and pattern recognition found in humans and intelligent animals (particularly bats), designed to assume operations in previously unknown, GPS-denied environments. It proposes novel electronics, aircraft, aircraft systems, systems, and procedures and algorithms that come together to form airborne systems which measure absolute ranges from a monocular camera via passive photometry, mimicking that of a human-pilot like judgement. The research is intended to bridge the gap between practical GPS coverage and precision localization and mapping problem in a small aircraft. In the context of this study, several robotic platforms, airborne and ground alike, have been developed, some of which have been integrated in real-life field trials, for experimental validation. Albeit the emphasis on miniature robotic aircraft this research has been tested and found compatible with tactical vests and helmets, and it can be used to augment the reliability of many other types of proximity sensors

Step by step: reconstruction of terrestrial animal movement paths by dead-reckoning

Background: Research on wild animal ecology is increasingly employing GPS telemetry in order to determine animal movement. However, GPS systems record position intermittently, providing no information on latent position or track tortuosity. High frequency GPS have high power requirements, which necessitates large batteries (often effectively precluding their use on small animals) or reduced deployment duration. Dead-reckoning is an alternative approach which has the potential to ‘fill in the gaps’ between less resolute forms of telemetry without incurring the power costs. However, although this method has been used in aquatic environments, no explicit demonstration of terrestrial dead-reckoning has been presented.Results: We perform a simple validation experiment to assess the rate of error accumulation in terrestrial dead-reckoning. In addition, examples of successful implementation of dead-reckoning are given using data from the domestic dog Canus lupus, horse Equus ferus, cow Bos taurus and wild badger Meles meles.Conclusions: This study documents how terrestrial dead-reckoning can be undertaken, describing derivation of heading from tri-axial accelerometer and tri-axial magnetometer data, correction for hard and soft iron distortions on the magnetometer output, and presenting a novel correction procedure to marry dead-reckoned paths to ground-truthed positions. This study is the first explicit demonstration of terrestrial dead-reckoning, which provides a workable method of deriving the paths of animals on a step-by-step scale. The wider implications of this method for the understanding of animal movement ecology are discussed

Estimating intrinsic camera parameters from the fundamental matrix using an evolutionary approach

Calibration is the process of computing the intrinsic (internal) camera parameters from a series of images. Normally calibration is done by placing predefined targets in the scene or by having special camera motions, such as rotations. If these two restrictions do not hold, then this calibration process is called autocalibration because it is done automatically, without user intervention. Using autocalibration, it is possible to create 3D reconstructions from a sequence of uncalibrated images without having to rely on a formal camera calibration process. The fundamental matrix describes the epipolar geometry between a pair of images, and it can be calculated directly from 2D image correspondences. We show that autocalibration from a set of fundamental matrices can simply be transformed into a global minimization problem utilizing a cost function. We use a stochastic optimization approach taken from the field of evolutionary computing to solve this problem. A number of experiments are performed on published and standardized data sets that show the effectiveness of the approach. The basic assumption of this method is that the internal (intrinsic) camera parameters remain constant throughout the image sequence, that is, the images are taken from the same camera without varying such quantities as the focal length. We show that for the autocalibration of the focal length and aspect ratio, the evolutionary method achieves results comparable to published methods but is simpler to implement and is efficient enough to handle larger image sequences

Low-Cost MEMS-Based Pedestrian Navigation Technique for GPS-Denied Areas

The progress in the micro electro mechanical system (MEMS) sensors technology in size, cost, weight, and power consumption allows for new research opportunities in the navigation field. Today, most of smartphones, tablets, and other handheld devices are fully packed with the required sensors for any navigation system such as GPS, gyroscope, accelerometer, magnetometer, and pressure sensors. For seamless navigation, the sensors’ signal quality and the sensors availability are major challenges. Heading estimation is a fundamental challenge in the GPS-denied environments; therefore, targeting accurate attitude estimation is considered significant contribution to the overall navigation error. For that end, this research targets an improved pedestrian navigation by developing sensors fusion technique to exploit the gyroscope, magnetometer, and accelerometer data for device attitude estimation in the different environments based on quaternion mechanization. Results indicate that the improvement in the traveled distance and the heading estimations is capable of reducing the overall position error to be less than 15 m in the harsh environments

Augmented Reality Audio Applications in Outdoor Use

Lisätyksi audiotodellisuudeksi (LAT) kutsutaan todellista äänimaisemaa, johon on lisätty virtuaalisia ääniobjekteja. Käyttäjän kuulema ääni tallenetaan LAT-kuulokkeisiin integroiduilla miniatyyrimikrofoneilla ja toistetaan tämän jälkeen suoraan käyttäjän korviin. Nauhoitetun signaalin päälle käyttäjälle voidaan toistaa keinotekoista tai aikaisemmin nauhoitettua signaalia. Binauraalisella prosessoinnilla lisätyt, virtuaaliset, äänilähteet voidaan sijoittaa haluttuun suuntaan. Virtuaaliset äänilähteet voidaan sitoa todelliseen äänikenttään binauraalisella prosessoinnilla, jos käyttäjän sijainti ja orientaatio tunnetaan. Käyttäjän jäljittämiseen käytettyjen menetelmien rajoituksista johtuen aikaisemmin toteutetut LAT-sovellutukset on tarkoitettu vain sisäkäyttöön. Tämän diplomityön tavoitteena oli suunnitella ja toteuttaa alusta ulkona käytettäviä LAT-sovellutuksia varten. Sekä inertiaan että maan magneettikenttään perustuvia menetelmiä käytettiin käyttäjän orientaation ja satelliittipaikannusta (GPS) paikan määrittämiseen. Alustan toimivuuden osoittamiseksi toteutettiin äänimuistisovellus suunnitellulla alustalla. Äänimuistia käytetään tallentamaan kaikki käyttäjän kuulema ääni, paikka- ja orientaatiotiedolla laajennettuna. Paikka- ja orientaatiotieto tallennettiin metatietona äänitiedostoon uudessa Ara-Wav formaatissa, jotta tietoa voidaan käsitellä myöhemminkin. Äänimuistisovellusta testattiin ja analysoitiin, minkä pohjalta alusta todettiin toimivaksi lähtökohdaksi ulkokäyttöön tarkoitettujen LAT-sovellusten toteuttamiseen.Augmented Reality Audio (ARA) can be defined as the real audio environment augmented with virtual sound objects. Everything the user hears is recorded with miniature microphones integrated in the ARA headset earphones. The recorded audio is immediately played back directly to the ears of the user. Along with the recorded signal, artificial or previously recorded sounds can be added. Binaural processing is used to position the virtual sounds in certain directions related to the user. The virtual sound sources can be fixed to the real environment with binaural processing, if the position and orientation of the user are known. Several ARA applications have been implemented before, but so far only to be used indoors, because of the limitations of applied tracking methods. The goal of the thesis was to design and implement a platform to be used outdoors. Inertial and magnetic tracking were used together to track the orientation of the user, and Global Positioning System (GPS) was used for position tracking. As a proof of concept, the Audiomemo application was implemented on the platform. Audiomemo can be used to record everything the user hears, and to enable the user to browse through previously recorded audio memories. The orientation and position information is saved as metadata in the audio file to enable retrieval of the information afterwards. The Audiomemo application was preliminarily tested and analyzed. The platform was found functional and a useful working base for ARA applications in outdoor use

A Comparative Analysis of Attitude Estimation for Pedestrian Navigation with Smartphones

International audienceWe investigate the precision of attitude estimation solutions in the context of Pedestrian Dead-Reckoning (PDR) with commodity smartphones and inertial/magnetic sensors. We propose a concise comparison and analysis of a number of attitude filtering methods in this setting. We conduct an experimental study with a precise ground truth obtained with a motion capture system. We precisely quantify the error in attitude estimation obtained with each filter which combines a 3-axis accelerometer, a 3-axis magnetometer and a 3-axis gyroscope measurements. We discuss the obtained results and analyse advantages and limitations of current technology for further PDR research

On Attitude Estimation with Smartphones

Accepted for the International Conference on Pervasive Computing and Communications (PerCom 2017), Mar 2017, Kona, United StatesInternational audienceWe investigate the precision of attitude estimation algorithms in the particular context of pedestrian navigation with commodity smartphones and their inertial/magnetic sensors. We report on an extensive comparison and experimental analysis of existing algorithms. We focus on typical motions of smartphones when carried by pedestrians. We use a precise ground truth obtained from a motion capture system. We test state-of-the-art attitude estimation techniques with several smartphones, in the presence of magnetic perturbations typically found in buildings. We discuss the obtained results, analyze advantages and limits of current technologies for attitude estimation in this context. Furthermore, we propose a new technique for limiting the impact of magnetic perturbations with any attitude estimation algorithm used in this context. We show how our technique compares and improves over previous works