Terrestrial laser scanner calibration and performance evaluation using the network method.

In this paper, we discuss two aspects concerning terrestrial laser scanners (TLSs) - error model calibration and performance evaluation. Error model calibration is the process of determining parameters of an error model to improve the accuracy of TLSs. Performance evaluation refers to a series of tests to determine if a TLS meets specifications provided by the manufacturer. Both procedures can be accomplished using a network of stationary targets whose locations are known from a prior calibration using another method/instrument. This paper explores the question of whether the network (i.e., target locations) must be calibrated using an instrument of higher accuracy such as a laser tracker (LT) or whether the TLS under study is itself suitable for network calibration. Regardless of whether an LT or a TLS is used, the calibration is performed from target measurements made from multiple locations of the instrument to average out systematic errors and reduce the uncertainties in target coordinates. Such multi-position measurements on stationary targets is referred to as the network method. We provide guidance on when the TLS is sufficient for network calibration and when an LT may be necessary for performance evaluation purposes.