M. Elizabeth Cannon

Development of an Integrated Low-Cost GPS/Rate Gyro System for Attitude Determination

The use of low-cost GPS receivers and antennas for attitude determination can significantly reduce the overall hardware system cost. Compared to the use of high performance GPS receivers, the carrier phase measurements from low-cost equipment are subject to additional carrier phase measurement errors, such as multipath, antenna phase centre variation and noise. These error sources, together with more frequent cycle slip occurrences, severely deteriorate attitude determination availability, reliability and accuracy performance. This paper presents the investigation of a low-cost GPS/gyro integration system for attitude determination. By employing the dead reckoning sensor type, the ambiguity search region can be specifically defined as a small cube to enhance the ambiguity resolution process. A Kalman filter is implemented to fuse the rate gyro data with GPS carrier phase measurements. The quality control system based on innovation sequences is used to identify cycle slip occurrences and incorrect inter-antenna vector solutions. The availability of the integrated system also improves with respect to the GPS standalone system since the attitude parameters can be estimated using the angular rate measurements from rate gyros during GPS outages. The low-cost hardware used to design and test the integrated system consists of CMC Allstar receivers with the OEM AT575-70 antennas and Murata ENV-05D-52 piezoelectric vibrating rate gyroscopes. Tests in the urban area demonstrated that the introduction of rate gyros in a GPS-based attitude determination system not only effectively decreased the noise level in the estimated attitude parameters but coasted the attitude output during GPS outages and also significantly improved the system reliability.

GPS/Reduced IMU with a Local Terrain Predictor in Land Vehicle Navigation

In order to reduce the cost and volume of land vehicle navigation (LVN) systems, a “reduced” inertial measurement unit (IMU) consisting of only one vertical gyro and two or three accelerometers is generally used and is often integrated with other sensors. Since there are no horizontal gyros in a reduced IMU, the pitch and roll cannot be calculated or observed directly from the inertial data, and the navigation performance is thus affected by local terrain variations. In this work, a reduced IMU is integrated with global positioning system (GPS) data and a novel local terrain predictor (LTP) algorithm. The latter is used primarily to help estimate the pitch and roll of the reduced IMU system and thus to improve the navigation performance. In this paper, two reduced IMU configurations and two grades of IMUs are investigated using field data. Test results show that the LTP is valid. Specifically, inclusion of the LTP provides more than an 80% horizontal velocity improvement relative to the case when the LTP is not used in a GPS/reduced IMU configuration.

Attitude determination using a multi‐antenna GPS system for hydrographic applications

A four‐antenna GPS attitude determination system was used to estimate roll, pitch, and heading parameters of a 52‐meter surveying vessel in an operational marine environment. The least squares algorithm for platform attitude estimation using multiple baseline vector observables is presented. An efficient on‐the‐fly carrier phase ambiguity searching method is derived, which utilizes the Cholesky decomposition method and the known baseline constraints between the GPS antennas to construct the potential ambiguity sets on the sphere. The accuracy of the estimated attitude parameters from the GPS multi‐antenna system was assessed with an independent inertial navigation system (INS). Results from sea trials show that the proposed GPS multi‐antenna system and processing algorithms delivered a satisfactory performance under various ship maneuvers. The accuracy of GPS estimated ship attitude parameters is better than 0.06 degrees at an output rate of 10 Hz. Such a performance demonstrates a new alternative means t...

Integration of Steering Angle Sensor with Global Positioning System and Micro-Electro-Mechanical Systems Inertial Measurement Unit for Vehicular Positioning

The concept of using the steering angle sensor to enhance positioning accuracy during Global Positioning System (GPS) outages is the focus of this article. This development of a GPS Micro-Electro-Mechanical Systems Inertial Measurement Unit (MEMS IMU) steering angle sensor vehicular positioning system is discussed in detail including the error dynamics and measurement models as well as integration strategy. With postmission and real-time field tests, the benefits in terms of the horizontal positioning accuracy after integrating the steering angle sensors are analyzed. With respect to GPS/MEMS IMU integrated system, the percentage improvement gained when including the steering angle sensor is over 50% for the open-sky test when GPS outages are simulated, and about 30% for the real-time tests conducted in the suburban and pseudourban environments.

GPS/Low-Cost IMU/Onboard Vehicle Sensors Integrated Land Vehicle Positioning System

This paper aims to develop a GPS, low-cost IMU, and onboard vehicle sensors integrated land vehicle positioning system at low cost and with high (cm level) accuracy. Using a centralized Kalman filter, the integration strategies and algorithms are discussed. A mechanism is proposed for detecting and alleviating the violation of the lateral nonholonomic constraint on the wheel speed sensors that is widely used in previous research. With post-mission and real-time tests, the benefits gained from onboard vehicle sensors and the side slip detection and alleviation mechanism in terms of the horizontal positioning accuracy are analyzed. It is illustrated by all the tests that GPS plays a dominant role in determining the absolute positioning accuracy of the system when GPS is fully available. The integration of onboard vehicle sensors can improve the horizontal positioning accuracy during GPS outages. With respect to GPS and low-cost IMU integrated system, the percentage improvements from the wheel speed sensor are 90.4% for the open-sky test and 56.0% for suburban area real-time test. By integrating all sensors to detect and alleviate the violation of the lateral nonholonomic constraint, the percentage improvements over GPS and low-cost IMU integrated system can be enhanced to 92.6% for open-sky test and 65.1% for the real-time test in suburban area.

Chapter 6 – Personal Style

Personal style and intentional branding will change and develop with your career. It may be particularly driven by the positions that you hold or the various functions that your job entails. Capturing the key aspects of the messages you want to convey in addition to your goals is key in projecting the career-appropriate personal style.

Chapter 8 – Personal Style

Publisher Summary This chapter illustrates the importance of developing a personal style. There are two distinct elements of personal style. The first is surface style that consists of visual elements (primarily dress and posture), and second, functional style that is a combination of nonverbal and verbal elements (facial expression, body language, tone of voice, vocabulary). These two aspects of style are far from being evenly weighted in the formation of the critical first impression. In every workplace there are three accepted ranges of style, with some variations, depending on ones location and culture. Although male counterparts lose some of their perceived authority when they dress more casually, the impact on their female counterparts is much more significant. Taking care to dress wisely may be even more important when starting a career. One strategy is to observe other successful women in similar environments and use their approaches to dress as a clue. Another is to consult the Internet and print media for some guidelines. A competent and capable scientist who consistently produces excellent results can become very successful. But one must recognize that choosing to adopt a personal style without considering the importance of both surface and functional styles in influencing the impact on others, and their acceptance of the work could make that success more difficult to achieve.

Submeter real-time differential GPS and attitude determination for unmanned navigation

The performance of real-time differential GPS navigation are affected by the satellite constellation available, the characteristics of user equipment, the data processing method used, the specifications of the data link used to broadcast the data from the reference station to the mobile platform, and the distance between the reference station and the platform. Each of the above parameters are discussed and related errors are quantified. The effect of user equipment characteristics such as code and carrier phase noise, multipath rejection capability, and number of tracking channels, is discussed. The use of latency is quantified as a function of the data processing method and receiver type used. Various aircraft positioning case studies are used to illustrate the capability of the system under various conditions. Attitude determination using a multi-antenna configuration is described, together with limitations due to fuselage stability and wing flexing. The results of various flight test are described to illustrate the performance levels achievable.