Measuring the standard baseline is a demanding project requiring both expertise and suitable weather conditions. The measurement is carried out using the Väisälä Interference Comparator, which determines length by analyzing light beams reflected between mirrors. Pictured is Research Manager Jorma Jokela.
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Nummela, a small town in Finland, is home to the world’s most accurate geodetic baseline, attracting industry experts, researchers, and surveying professionals from around the globe. Known as the Nummela Standard Baseline, this 864-metre measurement line is renowned for its unmatched precision, with a margin of error within one-tenth of a millimetre.
The line is used to calibrate the world’s most advanced electronic distance measurement devices, essential in the construction of dams, bridges, and nuclear power plants.
Researchers and industry clients have traveled from as far as East Asia to test their equipment against this unparalleled benchmark.
Originally, the Nummela Standard Baseline provided the scale foundation for Finland’s national maps. Today, it plays a critical role in validating cutting-edge distance measurement technologies, supporting industries requiring exact measurements.
The baseline is periodically re-measured to maintain its precision. The Finnish Geospatial Research Institute (FGI) under the National Land Survey of Finland recently completed the latest field measurements, an operation conducted roughly every 20 years.
Fieldwork is carried out using interferometric measurement techniques with an instrument known as the Väisälä Interference Comparator. This device measures distance by analyzing the interference of light beams reflected between mirrors. Proper weather conditions, such as thick nighttime cloud cover, are essential for the process, which was conducted throughout last autumn whenever conditions permitted.
“This is a challenging project, both in terms of technical expertise and weather requirements,” said Jorma Jokela, Research Manager at FGI. “During the autumn, we worked through the nights under heavy cloud cover, which offers ideal conditions for the measurements.”
The methodology used in Nummela was developed by the late Finnish academic Yrjö Väisälä, a celebrated geodesist, astronomer, and physicist. Nummela’s sandy ridge was selected as the location for the baseline due to its stable ground. Since its establishment in 1947, the line’s length has varied by only 0.7 millimetres.
Preliminary results from the latest measurements confirm the line’s length at 864.1229 metres, identical to measurements conducted in 2013 to a tenth of a millimetre.
The Finnish-developed technique has gained international recognition and has become a key export. The Nummela scale has been transferred to approximately 30 countries, including Estonia, Lithuania, Austria, Germany, Spain, China, and South Korea.
Nummela’s Standard Baseline remains a vital re
Source: www.helsinkitimes.fi
