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The use of a standalone Global Navigation Satellite System (GNSS) has proved to be insufficient when navigating indoors or in urban canyons due to multipath or obstruction. Recent technological advances in low cost micro-electro-mechanical system (MEMS) – based sensors (like accelerometers, gyroscopes and magnetometers) enabled the development of sensor-based navigation systems. Although MEMS sensors are low-cost, lightweight, small size, and have low-power consumption, they have complex error characteristics. Accurate computation of the heading angle (azimuth) is one of the most important aspects of any navigation system. It can be computed either by gyroscopes or magnetometers. Gyroscopes are inertial sensors that can provide the angular rate from which the heading can be calculated, however, their outputs drift with time. Moreover, the accumulated errors due to mathematical integration, performed to obtain the heading angle, lead to large heading errors. On the other hand, magnetometers do not suffer from drift and the calculation of heading does not suffer from error accumulation. They can provide an absolute heading from the magnetic north by sensing the earth’s magnetic field. However, magnetometer readings are usually affected by magnetic fields, other than the earth magnetic field, and by other error sources; therefore magnetometer calibration is required to use magnetometer as a reliable source of heading in navigation applications. In this thesis, a framework for fast magnetometer calibration is proposed. This framework requires little space coverage with no user involvement in the calibration process, and does not need specific movements to be performed. The proposed techniques are capable of performing both 2-dimensional (2D) and 3-dimensional (3D) calibration for magnetometers. They are developed to consider different scenarios suitable for different applications, and can benefit from natural device movements. Some applications involve tethering the magnetometers to the moving platform (like in cars and machinery applications). Other applications are related to portable navigation (smartphone navigation, whether for pedestrians or while driving). The developed framework was examined through experimental work to verify its performance and robustness. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-05-01 00:52:30.274

Contamination events at Oak Creek, which runs through Oregon State University Research lands, prompted investigations into alternate transport mechanisms for moving liquid effluent from OSU Diary lands to Oak Creek. Magnetometer surveys conducted at the Diary identified magnetic signatures spatially associated with sub-surface locations of drain tiles, a 12-inch pipe, and other features. These pipes may provide alternate methods of transporting effluent to Oak Creek. Magnetometer surveys in support of the contamination study identified an interesting variability in the Earth's local magnetic field. Magnetic signatures spatially associated with drain tiles appear strong in the western portion of the site, but fade out in the eastern part of the site. The cause of this variability was investigated by examining soil iron distributions. The Field-scale soil iron distribution was determined using a colorimetric analysis of extractions obtained from soil core samples. This study shows larger concentrations of iron in the western portion of the site where the magnetic signal is strong and lower concentrations of iron where the magnetic signal is lower. Tile-scale iron distribution over the drain tiles and in control units were analyzed using the same colorimetric technique. This study identified a disturbance to the natural iron distribution over the tile in the western part of the site due to soil mixing in the back-filled tile trench resulting in a contrast in the magnetic data. In the eastern part of the site, where there is no magnetic signature associated with the tile, the iron distribution over the tile looks similar to the control unit results. Analysis of the soils determined that excavating during tile installation disturbed soil horizons, but the iron has redistributed itself to the pre-tile configuration effectively erasing the magnetic contrast that existed shortly after tile installation. This project has shown that iron redistribution can adversely affect the ability of magnetometer surveys to identify drain tiles. This project also demonstrates that soils must be looked at as dynamic systems rather than the more common static system approach when evaluating the success of magnetometer surveys. Applying a dynamic view of soils can help ground-based remote sensing surveyors avoid costly, unproductive surveys. / Graduation date: 2003

One important part of inertial navigation is the estimation of the direction relative to the Earth’s geographic North Pole, the so called heading. In this project, a gyroscope and an accelerometer were used together in an Extended Kalman Filter with a quaternion as the state space variable, representing the attitude. Given the attitude of the system, measurements from a magnetometer were rotated to a horizontal coordinate frame in order to calculate the direction toward Earth’s magnetic North Pole. Comparing this direction with the angle toward the Geographic North Pole given by a GPS, the local magnetic declination was estimated with the purpose of correcting the heading in the future. Different methods for detecting disturbances on the magnetometer in order to automatically decide when it is to be trusted was discussed and evaluated. Routines for easily performing sensor calibration was created. The outcome of the project was a well working attitude estimation, simply performed calibration routines and a set of methods working together to detect magnetometer disturbances. / En viktig del av ett tröghetsnavigeringssystem är skattningen av riktningen relativt jordens geografiska nordpol, den så kallade bäringen. I detta projekt användes ett gyroskop och en accelerometer tillsammans i ett Extended Kalman filter med en quaternion som tillståndsvariabel för att representera attityden. Givet systemets attityd roterades mätningar från en magnetometer till ett horisontellt koordinatsystem för att beräkna riktningen mot magnetiska nordpolen. Genom att jämföra denna riktning med vinkeln mot geografiska nordpolen kunde den lokala magnetiska deklinationen skattas för att sedan användas i framtiden för att korrigera bäringen. Olika metoder för att detektera störningar på magnetometern för att automatiskt bestämma när den är störd diskuteras och utvärderas. Rutiner för att enkelt kalibrera sensorerna skapades. Projektets resultat var en väl fungerande attitydestimering, enkla kalibreringsmetoder samt ett par metoder för att detektera störningar på magnetometern.

Idag ses ett ökat intresse för användandet av rörelseanalys inom olika sammanhang t.ex. övervakning, dataspel och diagnostisk undersökning av personers rörelsemönster med mera. Optisk rörelseanalys är den teknik som finns mest idag, men de systemen är dyra och saknar lämplig mjukvara för klinisk användning. En forskargrupp vid centrum för medicinsk teknik och strålningsfysik (CMTS) forskning och utvecklings avdelning (MT-FoU) vid Norrlands universitetssjukhus har sedan 2007 jobbat med en produktidé som bygger på att skapa ett nytt mobilt system för rörelseanalys som kan användas i medicinska undersökningar. Ett Arduino pro mini kort samt ett 9-axligt prototypkort som består av MPU-6000 och en magnetometer HMC5883L är anskaffat för att tillverka ett system i detta syfte. Syftet med projektet har varit att skapa ett verktyg som kan samla in rörelsemönster för att sedan presentera resultatet i ett diagram. Systemet skulle kunna samla in data från en sensor som inkluderar en 3D-accelerometer ett 3D-gyroskop och en 3D magnetometer för att därefter skicka det vidare till en dator där mätdata presenteras visuellt och sparas undan i en textfil. En viktig detalj att ta hänsyn till vid konstruktionen av det nya systemet var att konstruktionen gjordes med hjälp av billiga standardkomponenter och kretskort. Projektet har genomförts och några testmätningar har gjorts. Ett resultat sparades undan i en textfil och ett diagram har tagits fram som beskriver ett lårs rörelsemönster vid normal gång.

Den obemannade  helikoptern Skeldar utvecklas av Saab Aeronautics. Saab är intresserade av hur väl sensorfusion kan användas för navigering av en obemannad helikopter. Med sensorfusion kan tillgängliga sensordata fusioneras. Det är mätningar från accelerometer, gyro, GPS och magnetometer som används av olika Kalmanfilter. Olika sensorfusionsmetoder föreslås, däribland Extended Kalman Filter (EKF) och ett heuristiskt filter för att visa på hur man intuitivt kan göra för att fusionera mätningar jämfört med det modellbaserade sättet som Kalmanfiltret erbjuder. För att skaffa sig en uppfattning om filtrets prestanda kommer orienteringen, där attityden är avgörande för stabiliteten, att valideras mot en AHRS. Vid reglering av helikoptern används återkoppling därför är det inte helt nödvändigt att navigeringen blir helt exakt. Sensorerna som används vid navigeringen utvärderas, dels med avseende på hur väl de uppfyller databladets specifikationer och dels med avseende på om sensorerna måste kalibreras och tillvägagångssättet för att göra detta.

Recovery of unattached offshore facilities or missing equipments is a challenging activity. Generally speaking, this activity involves a comprehensive procedure which includes: target characterization, searching, detection, verification, locating, reacquisition and salvage. Among them, target searching and detection are the most critical components of the whole procedure. The purpose of this investigation was dedicated in discussing the efficiency by the application of side-scan sonar, magnetometer and sub-bottom profiler simultaneously in searching, detecting, identifying and locating underwater stationary targets. Procedures of this research include: 1. Discussing the capabilities of instruments and verification cruises on target. 2. Discussing the salvage activity we conducted off Kaohsiung harbor on a depleted anchor. 3. Estimating the practicability of the methodology. According to the characteristics of these apparatus, the water depth, collected by echo sounder, is capable of expressing the relief of the seabed. Seabed sonographs, recorded by side-scan sonar, show that it is feasible to detect, verify and locate targets on the seabed. Sub-bottom profiler provides the sub-surface sedimentary information which can be used to detect buried targets. Magnetometer can detect environmental magnetic intensities, which can locate and determine the size of ferrous targets. Two depleted anchors were recorded off Kaohsiung harbor on the navigation chart. A recovery plan was then arranged which included 4 phases: collection of anchor characteristics, initial field survey and target detection, target verification and locating, target recovery. The underwater searching equipment employed in this activity include: side-scan sonar, sub-bottom profiler, magnetometer, echo sounder, underwater positioning system (include GPS), remotely operated vehicle (ROV) and professional divers. The offshore working platform used in this activity was R/V Ocean Research#3. Results of the initial search phase by side-scan sonar indicated there was only one potential target in the searching area. Follow up verification cruises confirmed acoustically that the target was an anchor with a piece of chain clogged on a block. The results of this investigation included the information such as the dimensions and the location of the anchor. Furthermore, the reason which caused the anchor being abandoned on the seafloor was derived. For underwater ferrous targets, such as anchor and chain cable, all of the aforementioned apparatus, have good potential for their detection and verification. It can be concluded that, applying these apparatus simultaneously can more effectively conduct searching, detecting, identifying and locating underwater stationary targets than by the application of a single instrument such as side-scan sonar system. Optical verifications of this target by ROV were attempted, nevertheless, were not success due to the difficulties in maneuvering OR#3 into proper position. An attempt to recovery this target by divers was arranged. But due to bad weather and rough sea state, the divers were not even allowed to dive. However, according to the experiences collected, a target reacquisition and recovery facility was built to fulfill the necessity of guiding divers to the target and lift it.

This work addresses the relevant errors of the anisotropic magnetoresistance sensor for inertial navigation systems. The manuscript provides resulting guidelines and solution for using the AMR sensors in a robust and appropriate way relative to the applications. New methods also are proposed to improve the performance and, reduce the power requirements and cost design of the magnetometer. The new compensation method is proposed by developing an optimization algorithm. The necessity of the sensor calibration is shown and the source of the errors and compensating model are investigated. Two novel methods of indoor calibration are proposed and examples of operating systems are presented.

Tübingen, Univ., Diss., 2002.

The goal of this paper is to design and implement a module to determine the rotation around three axes normal to each other. The paper is divided into six parts. The first part deals with the rate sensor - the gyroscope. It is explicated how the gyroscope is used for rotation measurement. The next part of the paper explains the acceleration sensor – the accelerometer, functioning as an inclination sensor. The third part analyses the magnetic field sensor – the magnetometer, functioning as an electronic compass. With each type of sensor, the problems of parasitic influences are discussed. The foregoing parts constitute the basis for the HW of the module design that is explained in the forth parts. It deals especially with components used for processing the sensor signals. The next part is a description of the software of the module. Here, the software of the particular sensors and measurement methods used with them are discussed. The last part describes the software of the control application in the computer. The attention is paid especially to processing data from the sensors and their compensation against parasitic influences.