Development and Implementation of Calibration Mathematical Models and Procedures for Precise Digital Level

Achieving the desired results and safety for any engineering project requires regularly review and check the technical specifications and accuracy of the geodetic instruments. Standard calibration models and procedures are exist for all geodetic instruments but it must be developed and modified to meet the standard for advanced precise digital level especially for deformation measurements. Digital levels are widely used for setting out engineering structures and monitoring the structural deformation because of their accuracy, in addition to the possibility of automatically collecting and storing data, which save time and effort required for observations. When performing measurements for an industrial building or construction site, due to the operation of various mechanisms and equipment, vibration occurs on the surface of the earth or on the concrete base, on which a tripod with a digital level is mounted. Under these conditions, the frequency and amplitude of the oscillations has a great effect on the observations of modern digital geodetic instruments. This paper investigates the accuracy of precise digital level observations (height differences and distances) for two cases which are: observations in laboratory and observations in the field (open area - outdoors observations with sun light and different weather condition than laboratory). The paper presents also two new suggested observations techniques for determining the collimation error (angle (θ)) of precise levels depending on least square theory which in turn provide a significant improvement of the suggested methods for determining the characteristic of digital levels. The research presents also experimentally the results of investigating the effect of (level – tripod) vibration on the digital level observations accuracy and suggest a practical technique to reduce the influence of the tripod-level vibration system on the resulted observations.