Resumen
The determination of distances consistent with the definition of the base unit of length in the International System of Units (SI), the SI meter, with uncertainties of less than 1 ppm for distances of several km in the open air is a current challenge that is being increasingly required for different applications, including calibration baselines, high precision geodetic metrology in singular engineering projects, and, generally, all those applications requiring optimal use of geodetic and surveying instruments, like deformation monitoring in critical sites.
The use of Electronic Distance Meters (EDMs) is limited by the required knowledge of the index of refraction of the propagating medium at the same level of accuracy, which has motivated the recent development of new two-color, refractivity-compensated, electronic distance meter prototypes. As an alternative, the use of Global Navigation Satellite Systems (GNSS) could benefit from their high scale stability although the lack of appropriate estimation of the uncertainties in
their sources of error and their unknown propagation to the final result during the data processing have prevented so far a rigorous uncertainty analysis and, therefore, the use of GNSS for absolute distance determination.
Stemming from our initial methodology for a GNSS-Based Distance Meter (GBDM), subsequently improved for baselines up to 5 km providing the baseline distance with the corresponding uncertainty rigorously propagated from the GNSS initial error sources (approach named as GBDM+), this proposal aims to expand our GNSS-based methodology with rigorous uncertainty propagation mainly in two directions: first, by increasing the range of application to distances beyond the 5-6 km tested so far; and second, by optimizing the methods and observable selection in terms of the resulting uncertainty not only for the optimal determination of every distance but ely dedicated optimization procedures, for the optimal determination of every azimuth and every height difference.
The resulting methodology will be transferred to three significant applications: well-controlled metrology infrastructures (calibration baseline planned to be located at INTA premises), deformation monitoring networks in critical sites (Cortes de Pallás monitoring network next to the largest hydrological power complex in Europe) and precise geodetic networks for large engineering works (CERN geodetic network).
Considering these characteristics, the project proposal is not driven by the resolution of specific problems linked to the associated thematic priorities of the Plan Estatal de Investigación Científica, Técnica y de Innovación 2021-2023, but has as a primary objective the advancement of knowledge related to metrology and all its possible applications in fields such as civil engineering, industry and space science. It has therefore to be considered as a project proposal under the category of non-oriented research, and, in particular, a Type B proposal, if the degree of consolidation of the main researcher is taken into account.
