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Introduction
Modelling techniques used for obtaining the 3D models can be divided into two main categories, namely terrestrial imagery and aerial imagery. Under terrestrial category, there are three more sub-techniques known as geometric modelling, photogrammetric method, and laser scanning (da Silva et al., 2014). Geometric modelling is the classical approach where the surveyor uses conventional surveying techniques to acquire terrain details, digital cameras to get colour information and basic 3D modelling software. This is different from the photogrammetric method where 3D object coordinates are calculated by bundle adjustment with simultaneous camera calibration, and it includes additional geodetic measurements (Abellan et al., 2010; Cuartero et al., 2010; Staiger, 2003). During its introduction, terrestrial laser scanner (TLS) has been widely used for the scanning of pipelines at the oil platforms. Currently, TLS has been implemented for the following applications such as as-built measurement of structure, heritage building conservation, slope measurements, road-accident mapping, forensic mapping, environmental studies and much more (Fröhlich and Mettenleiter, 2004; da Silva et al., 2014). The 3D TLS is a good ground base technique that captures the position and dimension of objects in a 3D format. It collects data in point cloud from millions of laser pulses or distance measurements using a stationed laser scanner and a digital single lens reflex camera. The output in 3D point cloud is stitched by target coordinates. The accuracy of the merging process is enhanced by increasing the number of the target. The data are then transferred to a high-resolution computer and converted into 3D models. The high quantity and precision of the measured points generate a more realistic 3D illustration of objects (Al-Kheder et al., 2008; Jorda et al., 2011; Cosarca et al., 2010).
A terrestrial 3D laser scanner measures points in a 3D space. The point is defined by three measurements, namely the distance to the object, the angle in the horizontal plane and angle in the vertical plane (Zogg, 2008). Laser scanner will calculate the three-dimensional coordinates when the measurements are taken, and the output is so-called point cloud. With the laser scanning method, accurate as-built data can be obtained (Fabritius, 2009). The advantage of TLS is that it can produce a 3D survey in a very short...