The upgraded PTB 600 m baseline: a high-accuracy reference for the calibration and the development of long distance measurement devices
Abstract
The calibration and verification of high-precision electronic distance meters (EDMs) requires well-characterized and calibrated geodetic baselines. As the length measurements are performed typically over several hundred metres in air, a thorough understanding of the environmental conditions is necessary. In the course of a major refurbishment, the 600 m baseline of the Physikalisch-Technische Bundesanstalt at Braunschweig, Germany, was equipped with a dense environmental sensor network. This paper presents the characterization of this novel reference baseline, including the calibration of the inter-pillar distances, and identifies the major sources of uncertainty for such a length standard. A preliminary expanded standard uncertainty (k = 2) of U ( l ) _{k=2}=\sqrt{( 6.2 \times 10^{-4} \: m )^2 + ( 7.6 \times 10^{-7} \, l )^2} is deduced for single-slope distance comparisons on the baseline. In the course of a full calibration, the additive constant cEDM of an EDM can currently be determined with an expanded uncertainty of U(cEDM)k = 2 = 6.1 × 10-5 m, and its scale correction sEDM with an expanded uncertainty of U(sEDM)k = 2 = 8.2 × 10-7. As an example, a femtosecond laser-based distance measurement over 600 m on this baseline is presented.
- Publication:
-
Measurement Science and Technology
- Pub Date:
- September 2012
- DOI:
- 10.1088/0957-0233/23/9/094018
- Bibcode:
- 2012MeScT..23i4018P