Determination of permanent corrections of ball reflectors

Today, there are many manufacturers of triple-prism, spherical reflectors with different mechanical characteristics. That is why there is a problem of matching the signal reflection center with the geometric one. The purpose of this work is to evaluate the methods of determining permanent corrections of electronic tacheometers, ball reflectors and to develop recommendations for their use. Method. To determine the instrument correction, a displacement interferometer is used. It contains a two-frequency He-Ne laser with a wavelength of l = 0.63 μm (red range). The study compared the results of length measurements by an interferometer and an electronic total station with a ball reflector.  This allowed determining the instrument correction. The research defined the constant correction of reflectors and total stations on the phase section of the field base using the method of created linear observations. Results. Experimental studies of ball reflectors of various manufacturers and Leica electronic tacheometers were conducted. The determination of constant instrument corrections of the total station and reflector using the displacement interferometer can be performed with an accuracy of 0.1 mm. This significantly depends on the accuracy of measuring lines with the total station. The use of ball reflectors with a built-in triple prism allows significant increase of distance measurement accuracy by reducing centering errors, considering the constant instrument correction (up to 0.4 mm for Leica 1201 total stations). Scientific novelty. The methods of determining permanent corrections of ball reflectors and total stations were investigated. The proposed method determines the measurement interval length with the exception of systematic constant correction of the electronic total station and reflector. Practical relevance. The use of ball reflectors is recommended for quick and unambiguous installation at points, convenience of their use for monitoring observations, as well as for increasing the accuracy of linear measurements due to the reduction of centering errors. In order to achieve high-precision measurements of short lines, it is recommended, according to the performed studies, to carefully determine the constant correction of the total station and ball prisms. This makes it possible to increase the accuracy of line measurements at least three times compared to the declared accuracy of the total station manufacturer.