Abstracts of previous student projects

3rd semester

2nd semester, 4th semester

2010

Autonomous Monocycle Robot Conducted by GPS Positioning

By: Iulian Batros, Valerio Ricci

Currently tasks on construction sites and supply of big stores are performed by human operators (moving crated, activating other devices, maintenance tasks). This project would like to highlight the use of a robot capable of performing these tasks using the GPS signals and to identify strengths and weaknesses of this study work.

Several advantages in terms of manufacturing and maintenance costs are to be considered when analyzing the benefits of this project work.

In this project, we propose the localization algorithm of a monocycle robot using differential GPS and a hybrid strategy for a reliable mobile robot in outdoor environment.

2008

Study of a Software-defined Galileo Receiver

By: Francesco Paggi

A single frequency Galileo SDR receiver is presented. The features and modulation of the Galileo signal are briefly listed; the differences with GPS signal are highlighted. A full description of the observations on the B channel of the E1 frequency signal is then presented, along with some results. The pilot C channel is then acquired and tracked, using a coherent integration. 

Data Acquisition in Assisted GPS

By: Andrei Marinescu and Dragos Catalin

The increasing number of mobile facilities has led to new openings in the market of Location Based Services (LBS) when nowadays applications like Turn by turn navigation to any address, Receiving alerts depending on your current position, Location Based Mobile Advertising, and E-911/E-112 services are becoming more and more common.

Assisted GPS has a crucial role in these applications, providing a precise location for the LBS user within few meters in just under 5 seconds, which is much faster than a standard GPS receiver. Another advantage when compared to a standard GPS receiver is the ability of indoor positioning. It's worth mentioning that the amount of energy needed in the case of A-GPS is much smaller than in the case of a normal receiver.

2006

EGNOS Software Receiver

By: Volodymyr Petrovskyy and Vyacheslav Tretyak

The need of accuracy and integrity of a GPS position led to the development of European satellite based augmentation system EGNOS. A software receiver is a flexible implementation of a receiver, where most of the signal processing is done in software. New algorithms and signals can be easily added or modified in this receiver. This project presents an EGNOS software receiver based on modifying an existing GPS software receiver. The receiver was implemented in post processing mode with the signal obtained from the GNSS L1 front end. EGNOS corrections were applied to GPS raw data measured by Topcon dual frequency receiver. The results showed the position accuracy reaching 1 meter level in stand-alone mode. This is a considerable improvement in the accuracy of GPS positioning.

2005

Differential GPS in marine and ideal environments

By: Marcus Fengler, Gediminas Veiverys, Kazimieras Bagdonas and Christian Have Pedersen

Unlike any other positioning method differential GPS made a breakthrough in global positioning and made it applicable to such science and industry spheres which require highest precision possible. However new applications rises new requirements and DGPS implementations become more and more complex. One of late applications is monitoring ocean surface level to a millimeter level with a help of GPS. The marine environment is unfriendly to GPS becauseof heavy multipath, increased humidity and constant variations in antenna normal, thus making DGPS a sentient matter. The aim of this project is to analyze DGPS and apply it to the data collected in two different environments on the surface of the Mediterranean Sea by the Barcelona University and at Aalborg University. DGPS methods and Kalman filters were implemented in MATLAB environment. The precision difference in both environments was investigated.

2004

Combined Differential GPS and RTK to position a Gokart using Kalman Filtering

By: Anders Skeie, Stephen Kwabena Kportufe, Alexandros Filippidis and Cristina Primo Calderón

The project describes tracking of a gakart in real time, using GPS receivers. The positions obtained are kalman filtered and further used for track analysis. This projectis done in cooperation with SnofruTech, an Aalborg based company, which proposed the project as a case study. In addition SnofruTech provided the equipment and field for testing. The main focus of this project, is to find a accurate and cheap way for SnofruTech to get a precise position o its gokart system. During the project two stages of testing were performed, the initial experiments (A) and the experiments with the company (B). Initial testing was performed at campus, while experiments with company were done at Mou a suburb of Aalborg. Radio links were used to transmit correction data from the base GPS receiver to the rover ans coordinates from the rover to computer. Direct communication between GPS receiver and computer was done using HyperTerminal, while all data processing was done using Matlab version 7. Since all results are affected by noise, several filters, such as Kalman, Max/Min, Average, to name a few, were implemented to reduce the noise of the sensors and improve positions of Gokart. It was concluded that the kalman filter performed better if sensor where combined with GPS positions. If additional sensors are implemented, the performance of the filters increases, if right parameters of noise have been chosen.

EGNOS Software Receiver

By: Kostas Dragūnas, Vitalijus Linikas, Xiangfu Meng, Usman Ahmed Zahidi and Jose Luis Corral Sanchez

Recent devellopments and modifications in satellite-based positioning systems and new augmentation systems raise the need for a flexible and easily modifiable technology to cope with the amendments. The software receiver is an enabling technology for flexible implementation of a receiver in which significant amount of signal processing is accomplished in software rather than in hardware. This report documents a prototype software EGNOS receiver (EGNOS receiver stands for EGNOS-capable GPS receiver). The CDMA signal structure associated with GPS and EGNOS provides demanding computational requirements, therfore, the receiver design is considered in post process mode. Receiver is able to do GPS and EGNOS signal acquisition and tracking. Real GPS and EGNOS data obtained from a RF frrontend is used for simulation of this algorithms. Satellites ranging capabilities are not considered. Obtained EGNOS signal trackingperformance is not satisfactory enough to extract real EGNOS data from the signals and requires improvements. Simulation of EGNOS corrections application to GPS pseudorangesis done by using real EGNOS data recorded from hardware EGNOS receiver. Raw GPS measurements obtained from the same hardware receiver is used for this simulation as well. This allowed testing and devellopment of algorithms with actual GPS and EGNOS data to verify their performance. Results show considerable improvement in the GPS positioning accuracy. Future refinement will include the transition from a prototype to a complete GPS EGNOS-enabled software receiver. The applicationhas been designed in order to show advantages of software receivers, where new algorithms and signals can be easily added or previously modified.

2003

Navigational System for an Autonomous Farming Vehicle

By: Darius Plaušinaitis, Jon Johansen Wedel, Frank Kofi Ocran, Ramūnas Dirmeikis and Saulius Pušinskas

Operating agricultural equipment accurately can be difficult, laborious or even dangerous. Autonomous control offers many potential advantages over human control; however, previous efforts to automate agricultural vehicles have been unsuccessful due to sensor limitations.

With the recent development in GPS precise positioning using RTK technology,  a receiver can measure a vehicle's position to within a few centimeters and heading to within 0.1°. This ability to provide accurate real-time information about multiple states makes RTK ideal for automatic vehicle control.

This project will attempt to design an RTK system for an autonomous farming vehicle. The focus will be on developing and implementing RTK algorithms.

GPS measurements like other survey measurements are not devoid of errors, the system utilizes the concept of DGPS to eliminate common errors. An extended Kalman filter is used to reduce noise and extreme errors in GPS measurements.

Test results obtained shows that different components of the algorithms worked well but the result of the overall system test showed that the specifications set could not be achieved.

GPS Based Train Control

By: Nicolaj Bertelsen, Marianne Knudsen, Peter Rinder and Rune Tvilum

Safety is a very important issue in train transportation. In Denmark the safety is guaranteed the through the use of a so-called train control system. The present Automatic Train Control is reliable but also very expensive. This project is focused on investigating if the GPS can be a realistic alternative to the current train control system.

The main focus of the project is to implement a system to calculate an accurate position of the train while it is driving. With an accurate position available it should be possible to implement the remaining parts of the complete train control system. This is however not a part of the project.

The carrier phase based differential positioning system was implemented in Matlab. Data was gathered with an epoch interval of 0.3 seconds, and the calculations were made in post-processing. Ambiguities were solved with the Clyde Goad method combined with s static Kalman filter, and the kinematics of the system were estimated with a dynamic Kalman filter.

To make the positioning system able to run in real-time, all calculations were supposed to be optimized and implemented in a DSP. Because of hardware delivery problems, the DSP implementation was postponed so only a simple and less accurate version of the algorithms was implemented.

A system test was carried out, to test the abilities of the Matlab program under realistic conditions. Also the DSP system was tested, mainly for computation speed and accuracy.

The results for the Matlab system test showed that it is possible to calculate accurate positions even under tough conditions, but some improvements could be done to make the system even more reliable in these cases. Regarding the test results for the DSP system, the calculations were done faster with a position not significantly different than in Matlab on a PC.

Based on the obtained results, it can be concluded that it is possible to get positions based on GPS with accuracy necessary for a train control system. Before starting an implementation of the entire train control system based on GPS some additional integrity tests should be carried out. It should be possible to obtain the necessary integrity, especially with the future implementation of the European positioning system Galileo as a backup for the GPS system.

2002

High Precision Tracking System for Virtual Reality Using GPS

By: Stephen Neuman Asamoah and Tue Klaus Kyndal

The key elements in this project was to investigate the dynamics of a kinematic system, and the real-time determination of the system's pose (position & orientation). To direct our investigations, we chose to focus on the development of a specific application. For this, we chose the virtual environment. Some virtual environment systems require a spatial tracking application for pose purposes. Several methods are currently used such as magnetic trackers etc. However, most of these systems only work in a restricted laboratorial environment. With the use of GPS technology, an outdoor system could be made. For such a system, the orientation and position are rather critical, and if there is a lag between head movement and visual feedback, the user perceives a temporal distortion effect. It is therefor necessary to develop a system that includes a predictive filtering technique such as the Kalman Filter. Real-Time Kinematic (RTK) GPS is used for the estimation of the user's position in the virtual environment. The problems concerning system orientation were not addressed in this project. Download project.

2001

Comparison of Methods of Accuracy Improvement in Kinematic GPS

By: Mindaugas Paukštė, Mindaugas Stonys, Jevgenij Gagac and Inga Paulauskaitė

This project documents the analysis and possible improvements of the positioning accuracy in static as well as in kinematic GPS setups using simple GPS receivers. The project describes a set of experiments performed by the group, and the results of post processing methods, including a code DGPS and Kalman filtering. Possible applications of Kalman filter trying to improve the accuracy of estimation of the position in static and kinematic setups are investigated. Algorithm for moving object coordinate estimation using Kalman filtering is derived. A filter, which is implemented in this project, tries to predict further moving object trajectory considering that a movement is linear with zero acceleration in X, Y, Z components. The filter algorithm decides what to believe more: the predicted movement trajectory. The errors and mismatches in the algorithm flow are discussed. Possible other improvement methods are briefly discussed. The code DGPS method of improving of positioning accuracy is applied for coordinates, and not for pseudo ranges, considering that measurement conditions are exactly the same for the rover and reference receivers. It is concluded that simple methods of GPS accuracy improvement, such as code DGPS are not very efficient or do not increase accuracy that much. Kalman filter applied for coordinates is not efficient, because kinematic GPS “noisy” measurements are not normally distributed about the mean value.

2000

Implementation of Kalman filter for double differenced real-time setup

By: Adeniyi Iyiade and Kofi Owusu-Nkansah

This project work describes how a centimeter level accuracy can be obtained in real-time setup. The real-time set up was achieved by using a serial communication prot to read the GPS receiver data from the Matlab workplace. In the report, the first part describes the communication protocol between the serial communication port and the receiver and this shows how Matlab can write to an read data from the receiver in real-time set up. The second part describes how data was processed using developed tool box and how a centimeter levelaccuracy was obtained for the rover position. To help provide current estimates of the position coordinates, we use the Kalman filter. It also determines up-to date uncertainties of the estimates for real-time quality assessments. Because of its optimum performance, we have adopted its use in reducing the associated noise in measurements.

Precise Real Time Positioning in Kinematic Mode

By: Audronė Kvedarienė

The purpose of this project was to investigate the real-time precise positioning in kinematic mode. It was found that a centimetre level accuracy is obtained using relative positioning and carrier phase pseudorange observables. Unfortunately, this method brings difficulties in measuring ambiguities and also needs expensive equipment - at least two GPS receivers with radio modems.

Implementation of the Kalman filter for double differenced phase and/or code observation in a kinematic setup

By: Dalia Prizginienė, Saulius Prizginas, Darius Popovas, and Kristina Radzevičiūtė

Today the satellite navigation technology, with its capability to provide accurate position information, plays a key role for a more efficient management of the available transport resources. A user having a GPS receiver, fitted to a vehicle, is able to constantly determine its location. But there are some users that need more accurate position then usual GPS receiver gives. The project was made in case to show the extensive opportunities of using GPS receivers in the precise kinematic applications. So the investigation was undertaken in advance to implement a system, which gets the actual and accurate position of the ground vehicle in real time and plots it on the map. The simulation of real time system in a kinematic setup was implemented. The objectives of this project are to use the Ashtech Z-12 GPS receiver in moving vehicle and improve accuracy of the position by using Double differential GPS and Kalman filtering. Corrected positions are to be plotted on the digital map. Measurements for dual point positioning were undertaken to fulfill a static and a kinematic experiments. Before starting to simulate real-time, the static experiment was realized to ensure that the Kalman filter and double differenced GPS data processing techniques are functioning. Afterwards, the kinematic experiment accomplished to simulate the real-time. The computed positions were plotted on the digital map.

Useful links:

> Project library

Danish GPS Center, Fredrik Bajers Vej 7C, DK-9220 Aalborg Ø, Denmark, Tel +45 9940 8362, E-mail: gpscenter(at)gps.aau.dk