Optinen lämpötilan mittaus ilman taitekertoimen määrittämiseksi

In optical length measurement, attaining a measurement uncertainty beyond a 10^−6 level is often precluded by inaccurate knowledge of the refractive index of air. In particular, large variations in temperature along the measurement path often prevent to adequately quantify the refractive index and thus the speed of light in the medium. To that end, this thesis presents an optical thermometer designed to measure an effective temperature of air over long distances. The temperature measurement is based on absorption spectroscopy at the oxygen A-band and is fully controlled by a microcontroller. With the measurement technique developed in the thesis, the thermometer can attain high accuracy without requiring calibration. The measurement uncertainty of the thermometer is strongly dependent upon the measurement distance and exhibits the least uncertainty for distances over 100 m. Preliminary experiments with 25 m path length showed a standard deviation of 0.2 K in the difference between spectroscopic and reference thermometer measurements, and the developed measurement technique should allow to further reduce the uncertainty.Optisen etäisyysmittauksen epävarmuutta huonontaa usein vaikeus määrittää tarkasti ilman taitekerroin. Erityisesti merkittävät spatiaaliset lämpötilavaihtelut mittausmatkalla vaikeuttavat taitekertoimen, ja näin ollen valonnopeuden, tarkaa määrittämistä. Tämän vuoksi tässä työssä toteutettiin optinen lämpömittari ilman efektiivisen lämpötilan mittausta varten. Lämpötilan mittaus perustuu hapen absorptiospektroskopiaan lähi-infrapuna-alueella, ja mittaus on täysin ohjattu mikrokontrollerilla. Työssä kehitetyllä mittausmenetelmällä on mahdollista saavuttaa hyvä mittaustarkkuus ilman kalibrointia. Mittausepävarmuus riippuu vahvasti mitattavasta etäisyydestä ja vähenee yli sadan metrin mittausetäisyydellä. Alustavat tulokset osoittivat 25 m mittausetäisyydellä olevan mahdollista saavuttaa 0.2 K keskihajonta spektroskooppisen ja referenssilämpötilamittarin mittaamien lämpötilojen erotuksessa, ja tuloksen pitäisi olla helposti parannettavissa

The European GeoMetre project : developing enhanced large-scale dimensional metrology for geodesy

We provide a survey on the joint European research project “GeoMetre”, which explores novel technologies and their inclusion to existing surveying strategies to improve the traceability of geodetic reference frames to the SI definition of the metre. This work includes the development of novel distance meters with a range of up to 5 km, the realisation of optical multilateration systems for large structure monitoring at an operation distance of 50 m and beyond, and a novel strategy for GNSS-based distance determination. Different methods for refractivity compensation, based on classical sensors, on dispersion, on spectroscopic thermometry, and on the speed of sound to reduce the meteorological uncertainties in precise distance measurements, are developed further and characterised. These systems are validated at and applied to the novel European standard baseline EURO5000 at the Pieniny Kippen Belt, Poland, which was completely refurbished and intensely studied in this project. We use our novel instruments for a reduced uncertainty of the scale in the surveillance networks solutions for local tie measurements at space-geodetic co-location stations. We also investigate novel approaches like close-range photogrammetry to reference point determination of space-geodetic telescopes. Finally, we also investigate the inclusion of the local gravity field to consider the deviations of the vertical in the data analysis and to reduce the uncertainty of coordinate transformations in this complex problem