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Validation of the Laboratory Calibration of Geodetic Antennas based on GPS Measurements (4308)

Philipp Zeimetz and Heiner Kuhlmann (Germany)
Mr. Philipp Zeimetz
Scientific Assistant
University of Bonn
Institute of Geodesy and Geoinformation
Nu├čallee 17
Bonn
53115
Germany
 
Corresponding author Mr. Philipp Zeimetz (email: p.zeimetz[at]igg.uni-bonn.de, tel.: + 49 228 733565)
 

[ abstract ] [ paper ] [ handouts ]

Published on the web 2010-01-14
Received 2009-11-19 / Accepted 2010-01-14
This paper is one of selection of papers published for the FIG Congress 2010 in Sydney, Australia and has undergone the FIG Peer Review Process.

FIG Congress 2010
ISBN 978-87-90907-87-7 ISSN 2308-3441
http://www.fig.net/resources/proceedings/fig_proceedings/fig2010/index.htm

Abstract

In relative GNSS positioning, the antenna effects are one of the accuracy limiting factors. Besides relative and absolute field calibration procedures, there is an absolute laboratory calibration procedure, which is used at the University o f Bonn. Since February 2009 a new antenna calibration lab, which is especially concepted for the antenna calibration, is operable. This paper presents some investigations on the accuracy of this calibration procedure. The results are mainly based on GPS height measurements and the comparison with the results from a precise levelling. For this purpose 121 baselines between the 8 pillars of an EDM calibration baseline site with distances between 18 and 1101 meters were analysed. The levelled height differences can be regarded as references, thus it is possible to quantify the absolute GPS-accuracy. Furthermore, the GPS-accuracy is an indicator for the antenna calibration accuracy. The measured height differences are usually smaller than 1-2 mm (maximal deviations), when using the L1 or the L2 frequency, thereby the standard deviation is 0.8mm in both cases. As expected, in case of the ionospheric free linear combination L0 the standard deviation rises up to 3 mm. This very high accuracy is possible, if besides other effects, the antenna effects are reduced to a minimum level (e.g. the differences between an individual calibration and a type calibration can reach several mm). It is not possible to quantify the accuracy exactly, because the antenna effect is only one of various remaining uncertainties. Thus, the effects due to the calibration uncertainties are smaller than s = 0.8mm, at least. This high accuracy can not be reached, if dominant near-field effects exist. Near-field effects, which can not separated from the behaviour of the antenna itself, limit the accuracy of the relative GPS. Such effects are present in some of the analysed baselines, too. Here, one special antenna-near-field combination causes height differences of several millimeters. The other GPS results show an exceedingly high accuracy and gives an idea of the high calibration accuracy.
 
Keywords: GNSS/GPS; Positioning; Engineering survey; GNSS antenna calibration; GPS; calibration accuracy; anechoic chamber; laboratory calibration; near-field

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