This part of ISO 17123 specifies field procedures to be adopted when determining and evaluating the precision (repeatability) of electro-optical distance meters (EDM instruments) and their ancillary equipment when used in building and surveying measurements. This part of ISO 17123 is applicable to reflector-type EDM instruments

only and is not designed to determine the precision of non-prism EDM types. Primarily, these tests are intended to be field verifications of the suitability of a particular instrument for the immediate task at hand and to satisfy the requirements of other standards. They are not proposed as tests for acceptance or performance evaluations

that are more comprehensive in nature.

This part of ISO 17123 can be thought of as one of the first steps in the process of evaluating the uncertainty of a measurement (more specifically a measurand). The uncertainty of a result of a measurement is dependent on a number of parameters. Therefore we differentiate between different measures of accuracy and objectives in

testing, like repeatability, reproducibility (e.g. between day repeatability), and of course a thorough assessment of all possible error sources, as prescribed by ISO/IEC Guide 98-3 and by ISO 17123-1.

These field procedures have been developed specifically for in situ applications without the need for special ancillary equipment and are purposefully designed to minimize atmospheric influences.