The evaluation of the accuracy and precision of measuring equipment is critical in order to achieve results that meet the specifications of a given project. Standard calibration models and field procedures exist for all traditional surveying instruments, but are still lacking for recently developed technologies like terrestrial laser scanners (TLS). The main reason is limited knowledge of errors that affect these systems, owing to the proprietary design of the scanners and their software, and the integration of many potential sources of error. Owing to the difficulty of separating the different error sources of TLS, it is proposed in this paper that a test procedure can assess the overall achievable precision for a scanner instrument without individual errors being known. The proposed tests are based on the International Organization for Standardization specifications for geodetic instruments (www.iso.org). The tests can be performed in either a controlled or uncontrolled environment, which is advantageous for on-the-job calibration. A pulsed terrestrial laser scanner (Leica Scanstation 2) was used as a test subject and the evaluation results indicated that the specific instrument performed well within the manufacturer's specifications.
An optimized compact-based method is introduced that verifies the distance measuring precision of surveying instruments. The paper describes the improvement of the compact based method not only in establishing a compact facility by using shorter lengths and folded path but also in the assessment process by implementing the official ISO standard for electronic distance measuring equipment (ISO 17123-4). The method produces statistically comparable results to ISO standards and is suited for regular instrument checks in institutions with limited space available.
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