In modern industrial geodesy, high demands are placed on the final accuracy, with expectations currently falling below 1 mm. The measurement methodology and surveying instruments used have to be adjusted to meet these stringent requirements, especially the total stations as the most often used instruments. A standard deviation of the measured distance is the accuracy parameter, commonly between 1 and 2 mm. This parameter is often discussed in conjunction with the determination of the real accuracy of measurements at very short distances (5–50 m) because it is generally known that this accuracy cannot be increased by simply repeating the measurement because a considerable part of the error is systematic. This article describes the detailed testing of electronic distance meters to determine the absolute size of their systematic errors, their stability over time, their repeatability and the real accuracy of their distance measurement. Twenty instruments (total stations) have been tested, and more than 60,000 distances in total were measured to determine the accuracy and precision parameters of the distance meters. Based on the experiments’ results, calibration procedures were designed, including a special correction function for each instrument, whose usage reduces the standard deviation of the measurement of distance by at least 50%.

This paper describes laboratory tests on a Leica AT401laser tracker. As the newer Leica AT402 model also uses the same firmware package, most of the results should also be valid for this device. First, we present the instrument’s firmware errors and the software used for testing. The ASME B89.4.19-2006 standard for testing laser trackers is briefly presented. The warm-up effect of the instrument is inspected with respect to both angle measurement and distance measurement. The absolute distance meter (ADM) is compared with a laboratory interferometer on a 30-meter long rail and also on a bench with automated movement of the carriage of the reflector. A time series of measurements for determining the additive constant is evaluated. A simple test of the stability of the distance measurement in field conditions is introduced. Most of the tests were carried out at the Research Institute of Geodesy, Topography and Cartography (RIGTC) and at the Faculty of Civil Engineering (FCE) of the Czech Technical University in Prague (CTU).

The paper describes a software called ATControl which is based on the Matworks Matlab high-level programming language. This software is under constant development by the author in order to collect geospatial data by measuring with the absolute laser tracker Leica AT40x (AT401, AT402). Commercially available software solutions are shortly reviewed and the reasons for developing the new controlling application are discussed. Advantages of ATControl concerning metrological traceability of measured distances are stated. Key functional features of software are introduced.

The article introduces a group of instruments called laser trackers and specificallyfocuses on one of them - Leica AT401. At the Research Institute of Geodesy, To-pography and Cartography the instrument has been tested both in laboratory andoutdoor conditions. Several significant errors in the instrument’s system softwarehave been found, mostly due to the creation of user-programmed controlling appli-cation called ATControl. The errors are related to a selection, a computation andan evaluation procedure of the refractive index of air. Finally, notes of the newmeasurement modes of Leica AT40x are given and a range of distance measure-ment is discussed.

The main aim of the research was to evaluate numeric procedures of the indirect determination of the group refractive index of air and to choose the suitable ones for requirements of ordinary and high accuracy distance measurement in geodesy and length metrology. For this purpose, 10 existing computation methods were derived from various authors’ original publications and all were analysed for wide intervals of wavelengths and atmospheric parameters. The determination of the phase and the group refractive indices are essential parts in the evaluation of the first velocity corrections of laser interferometers and electronic distance meters. The validity of modern procedures was tested with respect to updated CIPM-2007 equations of the density of air. The refraction model of Leica AT401 laser tracker was analysed.

The paper introduces testing procedures of several different geodetic centring devices performed mostly at the laboratory of the Research Institute of Geodesy, Topography and Cartography. Functional construction characteristics of a spherically mounted retroreflector Leica RRR 1.5’’, rotatable carriers Sokkia AP41 and Leica GZR3 and 12 different geodetic tribraches were examined. Further, a centring displacement instrument developed at the Czech Technical University in Prague, Faculty of Civil Engineering, Department of Special Geodesy, is evaluated in both laboratory and field conditions. For all tests, laser tracker Leica AT401 with a 5 μm standard uncertainty of absolute distance measurement, was employed.