In addition to its main purpose: establishing and maintaining the parameters of the height system for the territory of a given state (country), state levelling networks also serve to establish (register) the contemporary (recent) vertical movements of the Earth's crust. The detection of such movements, besides in a purely research sense, is of great practical importance. The displacement of the benchmarks over time plays an essential role in seismic forecasting in the short and long term. Sometimes, not very often, it happens that the duration of the measurements in a single cycle of State levelling network measurement is commensurate or nearly commensurate with the period between the different cycles. Such a fact raises serious issues to be addressed, both in the process of preliminary accuracy estimation of the measurements and in the formation of the adjustment model. A period of ten years or more is long enough for displacements on the order of a few mm (millimeters) to become apparent and to be reliably detected. One possible approach, in such cases, is to apply a modified version of adjustment using the Least Squares Method. It would be appropriate, as additional unknowns, to introduce the velocities of the individual benchmarks of the network into the adjustment model. Thus, taking into account the time of the start of the measurements, preconditions are created for taking into account the dynamic behaviour of the benchmarks during the measurement period. The applied adjustment model is based on the so-called "dynamic" or "kinematic" adjustment model, which also takes into account some technological features in the overall network measurement process.

This study will give a contemporary method for Quality Assurance or as-build during the construction of a building in Sofia, R. Bulgaria by using High Definition Survey (HDS) or more known as terrestrial Laser Scanning. Analyses were done on concrete casted elements (Floors, Ceiling Slabs and Columns) for the first eight floors which were already constructed during the time of field measurements. As a reference - data are obtained from the original design in native AutoCAD format, while field data were acquired by using 3D laser Scanners and they are represented in a form of Point Cloud. All data (design and measured) are acquired in local coordinate system and were later georeferenced in to the already established object coordinate system. The study will show the workflow for data preparation, post processing, and the results from 3D Inspection and Analyses. All tasks were implemented by two survey crews within 10 working days (four days for field work and 6 days for post processing analyses and reporting). During the laser scanning a total of 3 679 440 634 points were surveyed form 368 stations. After the post processing the number of points was reduced to 2 515 520 148 with relative accuracy after registration of individual scan worlds of +/- 3-4 mm. The accuracy for the data transformation in to the object coordinate system is +/- 7.5 mm. In order to have better data visibility and understanding of the deformations and displacements casted concrete elements were inspected separately floor by floor where ceiling and floor slabs were inspected in 1D (Z direction) while columns were inspected in 2D - (XY) inspection for the position. Thus some will say that the results are within accuracy limits of the classical measuring techniques we should not forget the fact that the percentage of inspected elements/surfaces is more than 95%.

<p>The North American Vertical Datum of 1988 (NAVD88) was established by the minimum-constrain adjustment of geodetic levelling observations in Canada, USA, and Mexico. It held fixed the height of the primary tidal benchmark at Rimouski, Quebec, Canada. The NAVD88 datum was never officially adapted in Canada due its large east-west tilt of 1.5 m from the Atlantic to Pacific coast (Hayden <em>et al.</em><em>,</em> 2012). Also, a large systematic difference (ranging from -20 cm to +130 cm) was found between NAVD88 and the pure geoid gravimetric models. Using Factor Analysis it was discovered that one of the factors, which can explain the tilt of the NAVD88, is the terrain, i.e. small in the flat states but large in the mountainous areas such as in the Rockies and the Appalachians (Li, 2012). A possible reason for the tilt of the NAVD88 might be the weights used into adjustment of the network. In this study the data of two precise national levelling networks are used, e.g. the Second Levelling of Finland and the Third Levelling of Bulgaria, in order to support the above hypothesis. An iterative procedure based on the Inverse Absolute Height Weighting (IAHW) is applied. The core of this procedure is to find this value of the power parameter (p) of the weights w=H<sup>p</sup>, where H is the absolute elevation difference of the terminals in the levelling lines, that minimize the mean of the mean squared errors (MSE) of the nodal bench marks (NBM) in both networks. It has been found that p=1 and p=4.3 for the Bulgarian and the Finnish networks, respectively. Also, a similar iterative procedure based on the Inverse Distance Weighting (IDW) is performed and the best decisions for the Finnish and the Bulgarian networks are obtained. It has been found that the weights w=L<sup>-5.9</sup> and w=L<sup>-1.6</sup>, where L is the length of the levelling line, lead to the minimal MSE of the NBM for the Finnish and the Bulgarian networks, respectively. The results of both the IDW and the IAHW procedures are compared. It has been revealed that the IAHW based adjustments lead to significantly less MSE of the NBM than all variants of the IDW. It has also been shown that concerning the Bulgarian and the Finnish analyzed here data, the IAHD approach leads to physically lower adjusted heights than the IDW. In some cases these differences are more than 1.5-2 times greater than the MSE of the corresponding bench marks.</p>

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The possible effect of the reductions to the measured distances between the points in a geodynamic geodetic network on the reliability of the subsequently calculated deformations has been analysed. Experimental investigations on the basis of doubly measured spatial chords from the real network and their analogues in UTM-projection have been planned and implemented. Reduction adjustments have been indisputably found to lead to distortion of the deformation model. The problem about block-determined Earth crust deformation has been discussed. A method for calculation of the elements of deformation by geodetic determined linear deformations has been proposed.