New Calibration Method Using Low Cost MEM IMUs to Verify the Performance of UAV-Borne MMS Payloads

Spatial information plays a critical role in remote sensing and mapping applications such as environment surveying and disaster monitoring. An Unmanned Aerial Vehicle (UAV)-borne mobile mapping system (MMS) can accomplish rapid spatial information acquisition under limited sky conditions with better mobility and flexibility than other means. This study proposes a long endurance Direct Geo-referencing (DG)-based fixed-wing UAV photogrammetric platform and two DG modules that each use different commercial Micro-Electro Mechanical Systems’ (MEMS) tactical grade Inertial Measurement Units (IMUs). Furthermore, this study develops a novel kinematic calibration method which includes lever arms, boresight angles and camera shutter delay to improve positioning accuracy. The new calibration method is then compared with the traditional calibration approach. The results show that the accuracy of the DG can be significantly improved by flying at a lower altitude using the new higher specification hardware. The new proposed method improves the accuracy of DG by about 20%. The preliminary results show that two-dimensional (2D) horizontal DG positioning accuracy is around 5.8 m at a flight height of 300 m using the newly designed tactical grade integrated Positioning and Orientation System (POS). The positioning accuracy in three-dimensions (3D) is less than 8 m

Airborne Navigation by Fusing Inertial and Camera Data

Unmanned aircraft systems (UASs) are often used as measuring system. Therefore, precise knowledge of their position and orientation are required. This thesis provides research in the conception and realization of a system which combines GPS-assisted inertial navigation systems with the advances in the area of camera-based navigation. It is presented how these complementary approaches can be used in a joint framework. In contrast to widely used concepts utilizing only one of the two approaches, a more robust overall system is realized. The presented algorithms are based on the mathematical concepts of rigid body motions. After derivation of the underlying equations, the methods are evaluated in numerical studies and simulations. Based on the results, real-world systems are used to collect data, which is evaluated and discussed. Two approaches for the system calibration, which describes the offsets between the coordinate systems of the sensors, are proposed. The first approach integrates the parameters of the system calibration in the classical bundle adjustment. The optimization is presented very descriptive in a graph based formulation. Required is a high precision INS and data from a measurement flight. In contrast to classical methods, a flexible flight course can be used and no cost intensive ground control points are required. The second approach enables the calibration of inertial navigation systems with a low positional accuracy. Line observations are used to optimize the rotational part of the offsets. Knowledge of the offsets between the coordinate systems of the sensors allows transforming measurements bidirectional. This is the basis for a fusion concept combining measurements from the inertial navigation system with an approach for the visual navigation. As a result, more robust estimations of the own position and orientation are achieved. Moreover, the map created from the camera images is georeferenced. It is shown how this map can be used to navigate an unmanned aerial system back to its starting position in the case of a disturbed or failed GPS reception. The high precision of the map allows the navigation through previously unexplored area by taking into consideration the maximal drift for the camera-only navigation. The evaluated concept provides insight into the possibility of the robust navigation of unmanned aerial systems with complimentary sensors. The constantly increasing computing power allows the evaluation of big amounts of data and the development of new concept to fuse the information. Future navigation systems will use the data of all available sensors to achieve the best navigation solution at any time

Accurate Calibration Scheme for a Multi-Camera Mobile Mapping System

Mobile mapping systems (MMS) are increasingly used for many photogrammetric and computer vision applications, especially encouraged by the fast and accurate geospatial data generation. The accuracy of point position in an MMS is mainly dependent on the quality of calibration, accuracy of sensor synchronization, accuracy of georeferencing and stability of geometric configuration of space intersections. In this study, we focus on multi-camera calibration (interior and relative orientation parameter estimation) and MMS calibration (mounting parameter estimation). The objective of this study was to develop a practical scheme for rigorous and accurate system calibration of a photogrammetric mapping station equipped with a multi-projective camera (MPC) and a global navigation satellite system (GNSS) and inertial measurement unit (IMU) for direct georeferencing. The proposed technique is comprised of two steps. Firstly, interior orientation parameters of each individual camera in an MPC and the relative orientation parameters of each cameras of the MPC with respect to the first camera are estimated. In the second step the offset and misalignment between MPC and GNSS/IMU are estimated. The global accuracy of the proposed method was assessed using independent check points. A correspondence map for a panorama is introduced that provides metric information. Our results highlight that the proposed calibration scheme reaches centimeter-level global accuracy for 3D point positioning. This level of global accuracy demonstrates the feasibility of the proposed technique and has the potential to fit accurate mapping purposes

A Comparison of Mobile Scanning to a Total Station Survey at the I-35 and IA 92 Interchange in Warren County, Iowa, August 15, 2012

The purpose of this project was to investigate the potential for collecting and using data from mobile terrestrial laser scanning (MTLS) technology that would reduce the need for traditional survey methods for the development of highway improvement projects at the Iowa Department of Transportation (Iowa DOT). The primary interest in investigating mobile scanning technology is to minimize the exposure of field surveyors to dangerous high volume traffic situations. Issues investigated were cost, timeframe, accuracy, contracting specifications, data capture extents, data extraction capabilities and data storage issues associated with mobile scanning. The project area selected for evaluation was the I-35/IA 92 interchange in Warren County, Iowa. This project covers approximately one mile of I-35, one mile of IA 92, 4 interchange ramps, and bridges within these limits. Delivered LAS and image files for this project totaled almost 31GB. There is nearly a 6-fold increase in the size of the scan data after post-processing. Camera data, when enabled, produced approximately 900MB of imagery data per mile using a 2- camera, 5 megapixel system. A comparison was done between 1823 points on the pavement that were surveyed by Iowa DOT staff using a total station and the same points generated through the MTLS process. The data acquired through the MTLS and data processing met the Iowa DOT specifications for engineering survey. A list of benefits and challenges is included in the detailed report. With the success of this project, it is anticipate[d] that additional projects will be scanned for the Iowa DOT for use in the development of highway improvement projects

A systematic approach to airborne sensor orientation and calibration: method and models

Avui dia, s'estima que el mercat de la geom atica mou pels volts de 30 bilions d'euros. Al darrera del creixement d'aquest mercat hi trobem noves tecnologies,projectes i aplicacions, com per exemple, \Global Positioning System"(GPS), Galileo, \Global Monitoring for Environment and Security"(GMES), Google Earth, etc. Actualment, la demanda i el consum de geoinformaci o est a incrementant i, a m es a m es, aquesta ha de ser precisa, exacta, actualitzada i assequible. Amb l'objectiu d'acomplir aquests requisits t ecnics i, en general, la demanda del mercat, la ind ustria i l' ambit acad emic estan introduint un darrera l'altre sistemes d'imatgeria, plataformes a eries i plataformes satel.litals. Per o alhora, aquests sistemes d'adquisici o introdueixen nous problemes com el calibratge i l'orientaci o de sensors, la navegaci o de les plataformes (de manera precisa i exacta segons el seu rendiment), la combinaci o de diferents tipus de sensors, la integraci o de dades auxiliars que provenen de diverses fonts, aspectes temporals com la gravaci o \cont nua"en el temps dels sensors, la feble geometria d'alguns d'ells, etc. Alguns d'aquests problemes es poden resoldre amb els m etodes i estrat egies actuals, sovint afegint pegats, per o la majoria no es poden resoldre amb els m etodes vigents o no es poden resoldre amb els m etodes vigents amb fiabilitat i robustesa. Aquesta tesi presenta les abstraccions i generalitzacions necess aries que permeten desenvolupar la propera generaci o d'ajustos de xarxes i m etodes d'estimaci o amb l'objectiu de resoldre aquests problemes. A m es, basada en aquestes idees, s'ha desenvolupat la principal eina d'aquesta recerca: la plataforma de software \Generic Extensible Network Approach"(GENA). L'objectiu d'aquesta recerca es establir les bases met odiques d'un concepte sistem atic per l'orientaci o i el calibratge de sensors aeris i provar la seva validesa amb nous models i aplicacions. Aix , en primer lloc, prenent dist ancia sobre el que s'ha fet tradicionalment i tenint en compte tot el que ens ofereix la tecnologia INS/GNSS, aquesta tesi genera un m etode per l'explotaci o dels sistemes INS/GNSS en l'orientaci o i el calibratge de sensors aeris. I, en segon lloc, s'han proposat i testejat amb dades reals alguns models que conformen aquest concepte, com per exemple, l' us de temps, posici o i actitud donats pel sistema INS/GNSS en mode relatiu (eliminant la necessitat dels par ametres d'absorci o d'errors INS/GNSS o la matriu d'orientaci o relativa IMU-sensor), l' us de temps, posici o, velocitat i actitud pel calibratge de temps (utilitzant aix la soluci o completa que donen els sistemes INS/GNSS per lligar les dimensions espacial i temporal) o reduir el nombre de mesures de l'orientaci o integrada de sensors tradicional, duent a terme la proposta \fast aerotriangulation", Fast AT. Aquesta recerca est a presentada a la tesi com un compendi d'articles. Aix doncs, els resultats de la tesi no s on nom es el document de la tesi en si mateix i les publicacions, hi ha tamb e un software comercial i models i aplicacions que validen el m etode proposat i representen un nou panorama per l'orientaci o i el calibratge de sensors aeris.En la actualidad, el mercado de la geom atica est a valorado en unos 30 billones de euros. Tras el crecimiento de dicho mercado, se hallan nuevas tecnologias, proyectos y aplicaciones, como por ejemplo, \Global Positioning System"(GPS), Galileo, \Global Monitoring for Environment and Security"(GMES), Google Earth, etc. Hoy en d a, la demanda y el consumo de geoinformaci on est a increment andose y, adem as, dicha informaci on debe ser precisa, exacta, actualizada y asequible. Intentando cumplir estos requisitos t ecnicos y, en general, la demanda del mercado, la industria y el ambito acad emico est an introduciendo uno tras otro sistemas de imagen, plataformas a ereas y plataformas satelitales. Pero a su vez, estos sistemas de adquisici on introducen nuevos problemas como la calibraci on y la orientaci on de sensores, la navegaci on de las plataformas (debe ser precisa y exacta teniendo en cuenta su rendimiento particular), la combinación de diferentes tipos de sensor, la integraci on de datos auxiliares que proceden de diversas fuentes, aspectos temporales como la grabaci on \continua" en el tiempo de los sensores, la d ebil geometr a de algunos de ellos, etc. Algunos de estos problemas pueden resolverse con los m etodos y estrategias actuales, generalmente aplicando parches, pero la mayor a no se pueden resolver con los m etodos vigentes o no se pueden resolver con los m etodos vigentes con fi abilidad y robustez. Esta tesis presenta las abstracciones y generalizaciones necesarias que permiten desarrollar la pr oxima generaci on de ajustes de redes y m etodos de estimaci on con el objetivo de resolver estos problemas. Es m as, basada en estas ideas, se ha desarrollado la herramienta principal de esta investigaci on: la plataforma de software \Generic Extensible Network Approach"(GENA). El objetivo de esta investigaci on es establecer las bases met odicas de un concepto sistem atico para la orientaci on y la calibraci on de sensores a ereos, y probar su validez con nuevos modelos y aplicaciones. As pues, en primer lugar, distanci andonos de lo que tradicionalmente se ha realizado y considerando lo que la tecnolog a INS/GNSS nos ofrece, esta tesis crea un m etodo para la explotaci on de los sistemas INS/GNSS en la orientaci on y la calibraci on de sensores a ereos. Y, en segundo lugar, se proponen y testean con datos reales algunos modelos que constituyen este concepto, como por ejemplo, el uso de tiempo, posici on y actitud dados por el sistema INS/GNSS en modo relativo (eliminando la necesidad de los par ametros de absorci on de errores INS/GNSS o la matriz de orientaci on relativa IMU-sensor), el uso de tiempo, posici on, velocidad y actitud para la calibraci on temporal (utilizando as la soluci on completa que dan los sistemas INS/GNSS para enlazar las dimensiones espacial y temporal) o reducir el n umero de medidas de la orientaci on integrada de sensores tradicional, llevando a cabo la propuesta \fast aerotriangulation", Fast AT. Esta investigaci on est a presentada en la tesis como un compendio de art culos. Resumiendo, los resultados de la tesis no son s olo el documento de la tesis en sí mismo y las publicaciones, existe tambi en un software comercial y modelos y aplicaciones que validan el m etodo propuesto y presentan un nuevo panorama para la orientaci on y la calibraci on de sensores a ereos.The geomatic market has an estimated value of some 30 thirty trillion euros. Behind this growing market, there are new technologies, projects and applications like Global Positioning System (GPS), Galileo, Global Monitoring for Environment and Security (GMES), Google Earth, etc. Modern society is increasingly demanding and consuming geoinformation that must be precise, accurate, up-to-date and affordable. In an attempt to meet these technical requirements and general market demand, industry and academia are introducing one imaging system, airborne platform and satellite platform after another. These acquisitions are introducing new problems such as calibration and orientation of the sensors, navigation of the platforms (with an accurate and precise processing of their individual performances), combination of different types of sensors, integration of auxiliary data provided from various sources, temporal issues of the ¿continuously¿ recording sensors, weak geometry of some sensors, etc. Some of the previous problems can be solved with current methods and strategies, oftentimes with a dose of patchwork. However, the vast majority of these problems cannot be solved with the current methods, or at least not with a like degree of robustness and reliability. This thesis presents the abstractions and generalizations needed to facilitate the development of the next generation of network adjustment and estimation methods that will make it possible to solve these problems. Moreover, the main tool of this research is a commercial software platform, ¿Generic Extensible Network Approach' (GENA), based on the proposed network approach. The goal of this research is to establish a methodical basis of a systematic approach to airborne sensor orientation and calibration and to prove its validity with newly-developed models and applications. On one hand, viewing the traditional DiSO and ISO from a distance and considering the possibilities that the INS/GNSS technology offers, this thesis generates a method to exploit the INS/GNSS systems for airborne sensor orientation and calibration. On the other hand, several models that constitute this method are proposed and tested with independent actual data sets; for example, the use of INS/GNSS-derived time, position and attitude in relative mode (avoiding the need for GNSS linear shift parameters, that absorb the INS/GNSS errors, or the relative orientation IMU-to-sensor, boresight, matrix), the use of INS/GNSS-derived time, position, velocity and attitude for time calibration (exploiting the full solution of the INS/GNSS systems to link the space and time dimensions) or the measurement reduction of the traditional integrated sensor orientation to perform the proposed "fast aerotriangulation", or Fast AT. This research is presented in the thesis as compiled papers. Therefore, the results of this thesis are not only the thesis document itself and a number of publications, but also a commercial software platform and models and applications that validate the proposed method and present a new panorama for airborne sensor orientation and calibration

Optimal Image-Aided Inertial Navigation

The utilization of cameras in integrated navigation systems is among the most recent scientific research and high-tech industry development. The research is motivated by the requirement of calibrating off-the-shelf cameras and the fusion of imaging and inertial sensors in poor GNSS environments. The three major contributions of this dissertation are The development of a structureless camera auto-calibration and system calibration algorithm for a GNSS, IMU and stereo camera system. The auto-calibration bundle adjustment utilizes the scale restraint equation, which is free of object coordinates. The number of parameters to be estimated is significantly reduced in comparison with the ones in a self-calibrating bundle adjustment based on the collinearity equations. Therefore, the proposed method is computationally more efficient. The development of a loosely-coupled visual odometry aided inertial navigation algorithm. The fusion of the two sensors is usually performed using a Kalman filter. The pose changes are pairwise time-correlated, i.e. the measurement noise vector at the current epoch is only correlated with the one from the previous epoch. Time-correlated errors are usually modelled by a shaping filter. The shaping filter developed in this dissertation uses Cholesky factors as coefficients derived from the variance and covariance matrices of the measurement noise vectors. Test results with showed that the proposed algorithm performs better than the existing ones and provides more realistic covariance estimates. The development of a tightly-coupled stereo multi-frame aided inertial navigation algorithm for reducing position and orientation drifts. Usually, the image aiding based on the visual odometry uses the tracked features only from a pair of the consecutive image frames. The proposed method integrates the features tracked from multiple overlapped image frames for reducing the position and orientation drifts. The measurement equation is derived from SLAM measurement equation system where the landmark positions in SLAM are algebraically by time-differencing. However, the derived measurements are time-correlated. Through a sequential de-correlation, the Kalman filter measurement update can be performed sequentially and optimally. The main advantages of the proposed algorithm are the reduction of computational requirements when compared to SLAM and a seamless integration into an existing GNSS aided-IMU system

An Analytical Investigation of Acquisition Techniques and System Integration Studies for a Radar Aircraft Guidance Research Facility

Boresight camera records for angular tracking accuracy of aircraf