Use this URL to cite or link to this record in EThOS:
Title: Optimal design of GPS networks : operational procedures
Author: Dare, Peter John
ISNI:       0000 0004 2704 0387
Awarding Body: University of East London
Current Institution: University of East London
Date of Award: 1995
Availability of Full Text:
Access from EThOS:
A method for the optimal solution for a particular aspect of Global Positioning System (GPS) networks has been devised. This relates to the logistics of the survey. In particular, it is the organisation of the fieldwork that has been addressed. This becomes especially important as the number of receivers used in a GPS survey increases. The minimum is two but there are marked efficiency gains by using at least one additional receiver. The problem addressed is to determine the order in which each GPS receiver should be moved between the points to be surveyed bearing in mind that it is necessary that the receivers have to be at certain points simultaneously so that the required observations are made. Techniques within the field of Operational Research (OR) have been used to solve this problem. The problem has been transformed into a more complex version of the Travelling Salesman Problem (TSP) -a classical combinatorial problem. With this transformation achieved it was possible to analyse the suitability of techniques within the OR field to solve the GPS logistics problem. A method for the optimal solution of the TSP was developed based upon an existing branch-and-bound approach but modified to take into account the more complex problem now being posed. This method, however, would only work for surveys where the surveyorsstarted and ended at a survey point. To be more realistic, the method was further enhanced to allow for a base (not a survey point) from which the surveyors would start and end their surveys together. This worked well, although it was restricted to surveys that were to be completed in one working period. This method, therefore, has been made more realistic by allowing the surveyors to return on a number of occasions to their base, thus simulating a survey lasting for more than one working period. The developed algorithms have been tested on examples with correct results. The above success is limited in that it cannot work for large networks and so an investigation into heuristic approaches was made. A heuristic approach does not guarantee optimality, but usually the solution is very close to it. This line of investigation was carried out as the guaranteed optimal solution is only possible in applications with a few number of points and receivers. In practice, three of four receivers may be used in networks containing over fifty points. For such a large network, a guaranteed optimal solution cannot be obtained in a sensible amount of time. Modern heuristic techniques have therefore been investigated with guidelines for their implementation to solve the GPS logistics problem given: - simulated annealing and tabu search seem to hold the most promise. A new approach based upon the use of a special fractal known as a space-filling-curve was also developed with successful results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available