The heights determined by Global Positioning System (GPS) refer to the ellipsoid called the World Geodetic System 1984 (WGS84). Global Geopotential Models (GGMs) that are available on GNSS commercial software are generally used to transform ellipsoidal heights to orthometric heights. In this study, the geoid heights of GPS/Levelling were computed to evaluate the accuracy of the geoid heights obtained from two GGMs, namely, the Earth Gravitational Model 96 (EGM96) and the Earth Gravitational Model 08 (EGM08). Seventeen (17) GPS/Levelling stations of the High Accuracy Reference Network (HARN) over Egypt were used for this purpose. The standard deviations for the differences between the geoid heights obtained through GPS/Levelling and those obtained from EGM96 and EGM08 were determined as ± 1.212 m and ± 0.543 m, respectively. This research confirms that the geoid heights obtained from EGM08 are closer to the geoid heights determined using GPS/Levelling over Egypt.
In recent years, there has been a notable growth in the recording and modeling of building processes due to the advent of construction information modeling (BIM). A BIM promotes better information exchange and encourages teamwork. The best way to swiftly gather buildings for BIM geometry is with laser scanning technology as opposed to the traditional measured method with a total station. The point cloud generated by laser scanners is heavily utilized by the BIM applications Autodesk Revit and Recaps. In this experiment, A 1350 square meter building at October University was scanned using a BLK 360 interior laser scanner to produce a 3D point cloud. The entire scanned area had 26 4inch-diameter black and white circular targets. Leica Cyclone 7.3 was utilized throughout the procedure to process the data collected. Different registration methods were used to create 3D models. (1) Auto Targets registration -(2) Cloud-to-cloud registration and (3) Manual registration. For each case, the accuracy evaluation is done using the control points by the total station instrument. Based on the results, the horizontal and vertical accuracy of the point cloud model from the registration methods were reasonably comparable.
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