Spectroscopic thermometry for long-distance surveying

Teemu Tomberg, Thomas Fordell, Jorma Jokela, Mikko Merimaa, Tuomas Hieta

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)


    Electronic distance meters are routinely used to accurately determine the distance between two points. To reach relative measurement uncertainties of 10-7, the average temperature along the beam has to be known within 100 mK since it is a key component in determining the refractive index of air. Temperature measurements at this level are extremely challenging over long distances and especially in an outdoor environment. This paper presents a thermometer for accurate temperature measurements over distances up to a few km. The thermometer is based on direct laser absorption spectroscopy of oxygen near 770 nm. The thermometer yields a spatially continuous measurement of air temperature, and it can provide spatially and temporally well-matching data with an actual distance-measuring laser beam. A field measurement campaign at the 864-m Nummela standard baseline demonstrates applicability of the developed thermometer for improving the refractive index compensation of current high-performance electronic distance meters.
    Original languageEnglish
    Pages (from-to)239-246
    JournalApplied Optics
    Issue number2
    Publication statusPublished - 10 Jan 2017
    MoE publication typeA1 Journal article-refereed


    • absorption spectroscopy
    • laser beams
    • refractive index
    • temperature measurement
    • thermometers
    • air temperature
    • continuous measurements
    • electronic distance meters
    • field measurement
    • laser absorption spectroscopy
    • outdoor environment
    • refractive index of air
    • relative measurement


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