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Pilot study on EDM instrument comparison

Project overseer
Jianshuang LI; Mingzhao HE

Project timeline
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Project description

EDM instrument is widely used in the fields of survey topography, meteorological monitoring and etc. There is no comparison for EDM instrument due to variety of calibration procedures and many factors that affect measurement results. Since APMP TCL meeting in 2015 in China, EDM comparison was discussed intensely. In APMP TCL the meeting in 2018, all TCL members agree to conduct a workshop together with pilot study. NIM have applied the EDM instrument comparison pilot study project, and been approved by TC chair in Feb 2019. 

The goal of this project is to study the calibration procedures and factors that affect EDM measurement results and reach a consensus on EDM instrument comparison.

The main tasks include

  1. The improvement of the baseline centering mechanism. NIM has designed, and manufactured the new centering plate and connector for baseline. NIM has also designed new connectors for EDM instrument and prism. NIM has also improved the software for the meteorological parameters auto-measurement system.

  2. The baseline long-term EDM measurement stability. The stability of baseline has been analysed by long-term stability and short-term stability. The long-term stability of baseline was monitored with the Leica absolute distance meter. The short-term stability of pillar spacing was checked before and after the EDM measurements.

  3. Onsite EDM measurement experiments. Over 7 NMIs include NIM, NMIA, NMISA, MSL, VMI, MASM and NMIJ have signed up for onsite EDM  experiments. However due to COVID-19 international travel is restricted,  onsite EDM experiments has been carried out without oversea participants in April and May 2021.

  4. Online EDM comparsion workshop. On November 10-11, 2021, 27 members from 11 NMIs have attended the Online EDM comparsion workshop. NIM have introduced the research results on EDM calibration since 2015. NMIA and VMI have also shared the progress on EDM calibration. 


NIM have carried out the onsite EDM measurement and online workshop. The outcome of this pilot study will give useful technical suggestions for formal EDM instrument comparison if revision to DimVim is needed. 

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