Journal of Surveying Engineering

Automated conversion of point cloud data from laser scanning into formats appropriate for structural engineering holds great promise for exploiting increasingly available aerially and terrestrially based pixelized data for a wide range of surveying-related applications from environmental modeling to disaster management. This paper introduces a point-based voxelization method to automatically transform point cloud data into solid models for computational modeling. The fundamental viability of the technique is visually demonstrated for both aerial and terrestrial data. For aerial and terrestrial data, this was achieved in less than 30 s for data sets up to 650,000 points. In all cases, the solid models converged without any user intervention when processed in a commercial finite-element method program.

Pile positioning, for driving piles below the surface of water in a marine pier construction project, is typically a time-consuming task owing to the fact that the pile wharf is affected significantly by environmental limitation and marine meteorology. As a result, it is always a goal to minimize the positioning time while maintaining a desired level of accuracy. This study developed a global positioning system (GPS)-based information system, which integrated six major modules. This system was designed to provide a real-time positioning and guidance solution for pile-driving barge control in a marine pier construction project. In a case study, the developed system has been implemented successfully in a real project and proved this system can improve the horizontal accuracy of real-time pile positions by less than 1 cm. It also contributed to a 42% reduction in the construction time and thus an 11% reduction in the final budget. Consequently, the efficiency of a piling construction project could be improved significantly by incorporating such a system.

A surveying-engineering procedure is presented for gravimetric geoid model verification along selected railway traverse lines using collocated ellipsoid and orthometric heights. The proposed method relies on (1) a tactical-grade, multisensor [Global Navigation Satellite System (GNSS)/inertial navigation system (INS)] kinematic-surveying system used to measure the ellipsoid heights along the traveled section and (2) the orthometric heights derived from the railway-line construction and/or maintenance works. Compared with the standard static GPS/leveling technique, the proposed approach produces geoid height profiles in a very short acquisition time, with dense point spacing, and in a considerably inexpensive manner. The quality of the final results reflects the accuracy of modern GNSS/INS systems and available rail-track orthometric height information. The method was applied to a long (101-km) railway traverse in central Greece using a custom-built mobile mapping system. Gravimetric geoid model verification was undertaken in an absolute and relative manner for the Earth Gravitational Model 2008 (EGM08) and 1996 (EGM96) geopotential models. Analysis of the results has demonstrated the potential of the method both in terms of efficiency and in terms of the evaluation checks performed. Based on the absolute- and relative-quality tests undertaken, the superiority of EGM08 over EGM96 is clearly evident for the tested line. Also, these results are cross compared and evaluated with the findings obtained from previous studies in Greece.

Light detection and ranging (LIDAR) scanners can rapidly collect high-resolution, centimeter-level-accurate point clouds representing topography, suitable for change detection if scans are repeated over time. To perform meaningful volumetric change analyses, point clouds are commonly triangulated to produce continuous, digital terrain models (DTMs). However, DTM creation methods generally require a fixed-look direction tied to a specific plane, which results in less than ideal triangulations when modeling areas with largely varying topography, such as coastal cliffs and beaches. Furthermore, for accurate volumetric change analysis, surfaces must be free of intersecting triangles, have consistent facet-normal orientations, and be free of data gaps (holes). The methodology presented herein produces continuous surfaces without inconsistent normals and minimizes holes and self-intersections. The few intersecting triangles and holes may be quickly repaired using existing algorithms and were shown to be substantially less abundant compared with common surfacing techniques. Finally, the data structuring of this technique significantly shortens processing time, reduces memory requirements, and enables efficient and interactive visualization through both subsampling at varying scales and optimized-view frustum calculations.