Studienarbeit 166

Investigations on multipath effects of GPS reference stations in Paraná and the First Baseline Calibration Station of Brazil (1a BCALBR) in Curitiba, PR.

von Bernhard Schäfer

Aufgabensteller: Prof. Dr.-Ing. B. Heck in Absprache mit Prof. Dr. C. Krueger [Curitiba, Brasilien]
Betreuer: Dr.-Ing. M. Mayer, Dipl.-Ing. A. Knöpfler, Prof. Dr. C. Krueger und MaSc. J. Freiberger [beide Curitiba, Brasilien], Prof. Dr.-Ing. Bernhard Heck
Interne Bibliotheksnummer: 166

The First Baseline Calibration Station of Brazil (1aBCALBR) is a result of the cooperation between the Department of Geomatics, UFPR, Curitiba (Brazil) and the Geodetic Institute, University Karlsruhe (TH), Karlsruhe (Germany).

The main objective of this study work was to investigate carrier phase multipath effects at the two pillars of 1aBCALBR, see Fig. 1 and Fig. 2. The 1aBCALBR is located at the Polytechnic Campus of the Federal University of Paraná (UFPR) on the roof top of a building near the Laboratory of Space Geodesy (LAGE) in Curitiba.

In addition, it should be elaborated if the multipath effects have changed, after the roof was painted with a special material in order to reduce the reflection of electro-magnetic waves. Different equipment (e.g. choke ring antenna (CR), ground plane antenna (GP)) was used. Altogether observation data of five GPS reference stations, separated in two campaigns, were processed by means of the software WASoft/Multipath 3.2.

The carrier phase multipath effects of all stations were calculated, presented, and compared. The first interpretation of the multipath maps leads to a ranking of the used reference stations. The PARA station receives GPS data which is very weakly affected by multipath effects. The GPS data of the pillars 1000 and 2000 of 1aBCALBR were of good quality, but the results varied with respect to the used equipment, see Fig. 3. The data of both other reference stations, which were operated by local companies, were strongly disturbed due to heavy multipath effects.

Based on the comparison of results calculated for identical antenna/receiver combinations pillar 1000 did show always stronger multipath effects than pillar 2000. This corresponds with the obstacle situation.

It also could be confirmed, that effects of multipath propagation on GPS data are depending on the used equipment. The choke ring antenna always showed the weakest multipath effects, but a significant difference between the geodetic antenna with and without ground plane (noGP) could not be recognised.

A comparison of the two campaigns carried out before and after the painting did not show any significantly different results.