Handling Low-Density LiDAR Data: Calculating the Heights of Civil Constructions and the Accuracy Expected

During the last years, in many developed countries, administrations and private companies have devoted considerable amounts of money to obtain mapping data using airborne LiDAR. For many civil activities, we can take advantage of it, since those data are available with no cost. Some important questions arise: Are those data good enough to be used for determining the heights of the civil constructions with the accuracy we need in some civil work? What accuracy can we expect when using low-density LiDAR data (0.5？pts/m2)? In order to answer those questions, we have developed a specific methodology based on establishing a set of control points on the top of several constructions and calculating the elevation of each one using postprocessing GPS. Those results have been taken as correct values and the comparison between those values and the elevations obtained, assigning values to the control points by the interpolation of the LiDAR dataset, has been carried out. This paper shows the results obtained using low-density airborne LiDAR data and the accuracy obtained. Results have shown that LiDAR can be accurate enough (10–25？cm) to determine the height of civil constructions and apply those data in many civil engineering activities. 1. Introduction LiDAR (light detection and ranging) system is a well-known technology to acquire mapping information. Efficiency and affordability have made LiDAR a primary tool for collecting a variety of high-quality surface data in much shorter periods of time than previously possible. In addition, hardware LiDAR technology has been significantly improved. Furthermore, the ranging accuracy improved to 2-3？cm level, and the availability of intensity signal became common [1]. These developments resulted in improved data quality in terms of higher point density and better accuracy, which, in turn, opened new application areas of LiDAR [2]. Modern LiDAR systems with the cm level ranging accuracy and high pulse rate, in theory, could be applied on topography works, like leveling processes [3], even more, ground-based LiDAR systems are being used to monitor movements of large structures and landslides, as a complement of other instruments, for instance, nonprism total station [4]. However, besides the laser ranging error there are several potential error, sources that can degrade the accuracy of the acquired data. LiDAR systems are complex multisensor systems and incorporate at least three main sensors: the GPS and INS navigation sensors and the laser-scanning device (Figure 1). Figure 1: LiDAR system components. There are multiple