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There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for nav- igation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and de ciencies that must be addressed. In many cases a pseudolite system with ground based transmitters has di culty in determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the problem of poor vertical observability is to use a height constraint, which is well known when travelling on a surface of water. For a ground-based vehicle, knowledge of the surface topography can be obtained, but cannot be readily used in the same manner as marine cases, since the height is often a varying function of position. This research investigates and develops ve methods of incorporating the known surface topography in a non-linear batch least squares estimation algorithm using carrier-phase measurements from pseudolites. The -oating point carrier-phase ambi- guities are estimated in this process. Real and simulated data sets are used to evaluate the performance of the ve algorithms. In simulation, all methods performed equiv- alently well on a -at surface. When simulating a hill, constraining the solution to lie in a plane tangent to the surface topography appeared to aid the solution with the best knowledge of the terrain. Use of a pseudo-measurement, a commonly used approach, did not provide the best results, and indicates the inadequacy of using this method for pseudolite-based systems. Results using data from a real system on a ground-based vehicle demonstrated sub-decimeter level positioning accuracy in all three dimensions.This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work.This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.
