Contribution of Pseudolite observations to GPS precise surveys

Although GPS has been widely used for precision surveys, many survey environments, like in urban areas, deep open-pit mines and valleys, limit the number of visible GPS satellites, deteriorating the survey accuracy. In addition some engineering projects require higher positioning accuracy in a particular direction. A GPS-only system hardly satisfies the requirements. Pseudolite-augmented GPS survey technique can strengthen the positioning geometry. Pseudolite (PL) measurements, however, suffer from various sources of errors different from GPS observations. In order to employ them for precise surveys these sources of errors must be treated properly. This paper discusses of the major sources of errors in PL measurements and the methodologies for their mitigation. Some experimental tests are then presented.Department of Land Surveying and Geo-Informatic