|
GEODEETTINEN LAITOS |
 |
08.06.2001 kirjasto@fgi.fi |
PUBLICATIONS OF THE FINNISH GEODETIC INSTITUTE |
|
|
| THE CHENGDU STANDARD BASELINE by Jokela J., M. Poutanen, Zhao Jingzhan, Pei Weili, Hu Zhenyuan and Zhang Shengshu Abstract Interference measurements and high-precision electronic distance measurements (EDM) were performed at the Chengdu Standard Baseline in Sichuan, China, in September-November 1998. The purpose was to improve the accuracy of the calibration baseline used by the Sichuan Bureau of Surveying and Mapping. All combinations of the 1488-m baseline were measured with the Kern Mekometer ME5000 of the Helsinki University of Technology and partly with the Väisälä interference comparator of the Finnish Geodetic Institute. Recent calibration results for the Mekometer were available from the Nummela Standard Baseline in Finland. The scale in interference measurements was obtained through use of a quartz meter system. These made it possible to determine lengths that are traceable to the definition of the metre. Small daily deformations of observation pillars presented a further challenge to interference observations. This was mostly caused by thermal expansion due to uneven warming of the massive constructions at the baseline. Minor longer-term movements were also possible. Satisfactory results were nevertheless obtained. Total standard errors of 0.03-0.07 mm in interference measurements and 0.1-0.2 mm in Mekometer measurements are normal. However, some pillar movements during autumn exceeded observation errors. Combining the results of the Väisälä comparator and the EDM instruments presented no problem, and the results from these two measurement methods fit well with each other. Most EDM instruments can be calibrated at the Chengdu Standard Baseline, but due to possible instability, regular control with high-precision EDM is recommended. |
|
08.06.2001 kirjasto@fgi.fi |
|
|
|
| Finnish Geodetic Institute Geodeetinrinne 2, P.O.Box 15 FIN - 02431 MASALA FINLAND |
|
: +358 9 2955 50