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DETERMINATION OF THE REPEATABILITY AND REPRODUCIBILITY OF THE SOLUTIONS PROVIDED BY AN ACTIVE GEODETIC NETWORK: APPLICATIONS TO CONSTRUCTION
Enrique Cano Jódar; Francisco Javier Mesas Carrascosa.
Keywords: GNSS, RTK, Repeatability, Reproducibility. 1. Introduction.
Surveying plays a very important role in all the phases into which the construction of engineering projects is divided. It is responsible for ensuring that the project execution coincides with the geometric characteristics of the design. As a result, methods and instruments that allow the work to be dynamic and accurate enough are necessary, so it achieves the required quality. Although surveying has not undergone major changes from a general conceptual point of view, the development of instrumentation, together with the development of computer science and electronics in the 1970s, allowed the incorporation of distance meters that, used together with optical equipment, led to the use of semi-total and total stations, all in an effort to automatically collect data. Consequently, the use of distance measurement offered a substantial change in terms of how surveying methods were applied. Undoubtedly, the implementation of satellite navigation systems (GNSS) starting in the 1980s represented an authentic revolution in the field of surveying and geodesy, yielding different positioning techniques, from the development of differential correction methods (Hofmann-Wellenhof, B, 2001) to real-time data gathering techniques (RTK, Real Time Kinematik) (Remondi B, 1985). Depending on the spatial quality required by the user, GNSS systems can be applied to survey networks, surveys and stakeouts.
However, the application of these systems is not free from limitations in terms of performance and effective work. The emergence of Active Geodetic Networks starting in the 1990s (Fotopoulos et al, 2001, Rizos C, et al, 2002, Alves et al, 2006, Aponte et al, 2009) allowed us to overcome these limitations by increasing performance in survey work applied to construction. It is in this context that we consider the determination of the repeatability and reproducibility of the solutions provided by an Active Geodetic Network as applied to construction, by using the UNE 82009- 2:1999 standard, equivalent to the ISO 5725-2:1994 international standard.
2. Methods and Materials.
The UNE 82009-2 standard (Accuracy (trueness and precision) of measurement methods and results, AENOR, 1999. Basic method for the determination of repeatability and reproducibility of a standard measurement method) was used to determine the repeatability and reproducibility of an active geodetic network. In planning this validation methodology, a number (p) of laboratories are set up in which a number of levels (q) are tested with the same number (n) of repetitions in each level, with identical repeatability conditions considered for each laboratory. The general term for designating the variability present between repeated measurements is precision. The standard considers repeatability and reproducibility as two types of precision for determining the variability of a measurement method, with two terms delimiting the precision: the repeatability characterizes the smallest variation, while the reproducibility the maximum variation.
In applying this standard to an active geodetic network, a set of three reference stations were considered as the laboratories. These stations will yield the position (x, y, z) of a general of six control points or levels, with a total of 90 measurements taken for each. The real-time correction method used in the position determination was the Master Auxiliary Concept (MAC) (Euler H.-J, 2001, N. Brown, 2005), a simple solution from the selected station. In this case, the selected station
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