Jokinen, Jarmo 1995

GPS in spatial data production and its use in urban areas

The purpose of this thesis is to introduce the latest GPS techniques and research the applicability of GPS in urban areas. The study deals with the basis of spatial data capture, field work which have need of surveying in urban area and the applicable GPS systems for those purposes.
The use of GPS has been directed to the higher class control point surveying this far, but the development of rapid static modes has made it a more effective technique also in control point surveying of local networks. The GPS-traverses are measured between known higher class points. Then the new points are adjusted in a WGS84-system and transformed to the local coordinate system using local transformation parameters which have been determined in connection with higher class GPS control point surveying. GPS/GIS is the subject most interest in surveying nowadays. Differential and kinematic GPS/GIS systems which use numeric spatial data have been developed. Using real-time systems it is possible to deal with settings out and mapping when post-processing systems have only data capture capabilities. There are many different needs concerning the positioning accuracy. The most advanced systems are capable of centimetre level accuracy. There are also lot of other jobs where GPS is used as a positioning device, for example in vehicle positioning.

For this thesis some test measurements were made in Klaukkala and Tampere. The basic idea was to research the usability of GPS in different types of measurements also in practice. There was made local control point surveying in Klaukkala test field using Ashtech Z-XII receivers and rapid static mode. The observation session was only about 5 minutes. Mapping and settings out were also tested in Klaukkala using Trimble's real-time kinematic GPS-system. GPS test measurements in urban areas were made using Ashtech's system in the centre of Tampere city where a building site limited the satellite visibility and affected multipath errors.