FIG Peer Review Journal


From Passive to Active Control Point Networks – Evaluation of Accuracy in Static GPS Surveying (6446)

Pasi Häkli, Ulla Kallio and Jyrki Puupponen (Finland)
Pasi Häkli
Research scientist
Finnish Geodetic Institute
Geodeetinrinne 2
Corresponding author Pasi Häkli (email: pasi.hakli[at], tel.: +358929555222)

[ abstract ] [ paper ] [ handouts ]

Published on the web 2013-02-02
Received 2012-10-30 / Accepted 2013-02-02
This paper is one of selection of papers published for the FIG Working Week 2013 in Abuja, Nigeria and has undergone the FIG Peer Review Process.

FIG Working Week 2013
ISBN 978-87-92853-05-9 ISSN 2307-4086


Active GNSS stations have become more and more essential for surveying during the past decade. Positioning services, like network-RTK, have revolutionized the surveying practices and challenged traditional control point networks and way of measuring them. In Finland network-RTK services are provided by private companies. Together with non-existent binding regulations, the definition of the national ETRS89 realization, EUREF-FIN, is based on traditional passive networks instead of active GNSS stations. The change from passive to active definition of control point networks would also require comprehensive change in measuring principles. Until present days the surveyors making geodetic measurements have been obliged to do the measurements hierarchically relative to nearest higher order control points. Since average spacing of active stations in network-RTK services is approximately 70 km and for passive networks much less depending on hierarchy class, would the use of active stations require measurements neglecting the hierarchy of the passive networks. However, even if passive networks still define the reference frames in Finland, greatly increased use of network-RTK services both in real-time and post-processing have changed the definition in practice. Since many users are already using these positioning services, is the access to the EUREF-FIN reference frame in such cases through active stations. Many advantages like easiness to use, smaller investments to own GNSS instruments and cost-effective measurements have raised opinions whether the traditional way of measuring is still valid today. Also the need and future of control points have been questioned by many surveyors. To partly answer these questions this study is evaluating the accuracy of static GPS surveying through active stations and with respect to the official passive control point networks in EUREF-FIN. As a result of this study it can be concluded that the consistency of static GPS surveying from active GNSS stations with respect to the official hierarchical passive control point network is in the order of 1–3 cm (68%), however showing some systematic features. An issue needing more careful consideration is determination of ETRS89 coordinates for active GNSS networks. Finland, being under influence of postglacial rebound phenomenon, challenges accurate determination of national ETR89 coordinates for wide-area reference station networks. The results suggest that the accuracy obtained in this study could be improved by correcting for postglacial rebound effect.
Keywords: GNSS/GPS; Positioning; Reference frames; active stations; passive stations; GNSS; VRS; network-RTK; control point; positioning accuracy