Scanning Near-shore Intertidal Terrain Using Ground LiDAR

Intertidal zone refers to the area under and above the water during high and low tides. Traditionally, this zone is not within the scope of land management authorities. Moreover, in accordance with principals set out by existing plans, intertidal zones are excluded from management zones. Boundaries should therefore be set at the land and sea border. Traditionally, methods in determining this have included the traditional theodolite (total station) method, mapping and aerial photography (photogrammetry). However, existing operational restrictions lower efficiency, in addition to increasing time and operational costs. Therefore this paper explores the practicality of a user- friendly, ground-based high resolution laser scanning technology. This method offers easy operation and high-density characteristics with an instrument platform that can be installed on elevated rooftops. High accuracy and resolution is achieved using a stop-and-go method producing Digital Terrain Model (DTM) data. The range of the completed data is 61km in length, 2.5km in width, and -0.5m depth, with a sampling error of approximately ±2cm. Through the implementation discussed in this research, accurate information about the changes of topography in intertidal areas can be obtained

Side Resistance of Drilled Shafts Socketed into Rocks for Serviceability and Ultimate Limit States

This study evaluates the analysis models of side resistance in rock sections by utilizing a wide variety of load test data. Available analytical models including the empirical adhesion factor versus the rock’s uniaxial compressive strength and its root are analyzed and compared statistically to determine the optimum relationships. The interpretation criteria for the L1 and L2 methods are used to analyze the load test results for serviceability and ultimate limit states, respectively. The analysis results show that the relationship model with the empirical adhesion factor versus the root of the rock’s uniaxial compressive strength exhibits better correlation than the one with the rock’s uniaxial compressive strength. Moreover, the general coordinate axes regression equation demonstrates better reliability than the semi-logarithmic and full logarithmic axes equations for both limit states. Based on these analyses, specific design recommendations for the side resistance of drilled shafts socketed into rocks are developed and provided with the appropriate statistics to verify their reliability

Improvement of LiDAR Data Accuracy Using 12 Parameter Affine Transformation

LiDAR data in a local coordinate system may need to be georeferenced and converted into a geographic or projected system. In coordinate transformation, the 7-parameter Helmet transformation method is usually used in measurements to eliminate the systematic errors made by a laser scanner. However, 7-parameter coordinate transformation assumes that there is only one scale error in all of the systematic errors. This study used 12 parameter affine transformation for coordinate transformation of airborne LiDAR data and terrestrial LiDAR data. The LiDAR data accuracy results upon 6-parameter similarity transformation, 7-parameter similarity transformation, and 12-parameter affine transformation were compared. The results showed that using 12-parameter affine transformation the airborne LiDAR and terrestrial LiDAR data have 2-3 times greater accuracy than do 7-parameter or 6-parameter transformations