Laser Scanning in Road Profiling - Coursework Example

Laser Scanning in Road Profiling Name: Lecturer: Course: Date: Introduction Road surface profiling is an essential constituent of road engineering (Acuity 2014). The activity is of particular significance to road builders, the government and contractors, since it is a primary source of data on micro- and macro-structures, roughness and longitudinal profiling. The roughness value allows the engineers to determine the co-efficient of friction. Using the data on road profiling, engineers are also able to determine the coarseness, as a result enabling them to compute the ride comfort of a road (Grafe 2007, P. 196). To this end, laser scanning comes in handy as a high-tech method of collecting real-time continuous express dimensions of the longitudinal profiles of a road’s surface. Current laser scanning equipment use non-contact laser sensors to determine the distance between surface of a road and the sensor. The equipment also has an accelerometer, whose functionality is subject to the speed of the vehicle. This paper explores the implications of laser scanning in profiling of road surfaces. Accordingly, the features of the equipment are detailed out with respect to their functionalities. Further, the advantages and disadvantages of using the equipment in road profiling are discussed. Implications of Laser-scanning in Road Profiling Laser-scanning technology is an important tool for road mapping. As pointed out by Gunnar (2008, P. 37), the technology has found wide application in road profiling, with modern ones such as kinematic laser-scanning forming a critical component of Mobile Road Mapping System (MoSES). The mobile technology promotes smooth traffic flow in busy highways by preventing obstruction. Presently, laser scanning technology forms part of the set of kinematic survey technologies in use by road surveyors. Indeed, kinematic laser scanning has replaced the static measurements that were traditionally used in determining road dimensions. It is further submitted that laser scanning technology has augmented accuracy and precision. This is since the kinematic survey methodology allows surveyors to achieve measurements of high precision. The laser-scanning technology is highly flexible and adaptable to diverse work environments. It is critical to observe that the lasers are distance-measuring lasers that can be suspended some 30cm from the road surface. The laser-scanning system integrates trajectory module and a two-dimensional scanner that is designed in a manner that allows it to be operative in profiling module. The advanced laser-scanning systems, on the other hand, have three-dimensional mapping capabilities (Palaska et al. 2006). Additionally, the scanners are calibrated and can be positioned orthogonally to the direction the vehicle is moving. As observed by Jean and Lars (2006, p.68), current advanced laser-scanners have high resolutions of nearly 1mm, along with outstanding point density. However, the profile frequency is subject to the driving speed. The laser-scanning system also has an accelerometer or an inertia system and an odometer. The odometer determines the distance attained by a vehicle, while the accelerator compensates the impacts of the vehicle acceleration. The accelerometer is capable of sensing the vehicle movement in the vertical plane. It also determines a datum reference that is in movement, through which the dimensions determined by the lasers are incorporated. It is therefore reasoned that such capability makes the data gathered by the laser-scanning system to be less independent on the vehicle’s speed. This perspective is shared by Schulz and Steiner (2005, P. 46). To this end, the speed of the vehicle has to be beyond 25km/h. It must also be assumed that the vehicle maintains minimal speed variation. In respect to road profiling, the laser-scanning system’s equipment uses algorithms to process signals. During the process of determining the distance, the sensors of the scanner project laser beams that create a spot on the road surface. Similarly, light beam is reflected from the spot. Additionally, angle positioned inside the sensor perceives the reflected light. Ultimately, the data gathered is transmitted to the processor for instantaneous processing. The laser scanning sensors are also modified to generate low noise and digital output of nearly 9.4 kHz. This means that they are designed to conform to the standards for profiling applications in pavements and roads. Additionally, the laser-scanning sensors redress vibrations, vehicle speeds, sunlight, temperature and types of surface. The laser-scanning system can acquire data at highway speeds. It samples the elevations of the road surface at intervals of 3 to 25 cm. The data acquisition system is designed to collect measurements in terms of kilohertz. The acquired data is controlled with the precision of relatively high resolution and static survey (Parry & Marsh2003, P. 54). Participants involved in road construction and maintenance, such as the government and road builders use the acquired data to determine the roughness index in inches per mile or mm per m. For extremely rough roads, the values of the roughness index range from zero to some mm/m. The government, in particular, applies the roughness index values in managing roads and in monitoring the road safety and quality issues. Application of laser-scanning system in profiling roads has a range of advantages. It is a time-saving technology with low associated costs. This implies that it is in wide application for mobile road mapping. Additionally, the laser-scanning techniques are swift and give precise results. Next, the systems are superior to static methods that provide consistent and invariable point densities. Despite the advantages, several limitations stand in the way of their effective application. First, the dimensions of road profiles tend to be subjective since they are dependent on the targets that are susceptible to dynamic change. Further, the laser scanner’s accuracy is dependent on a range of factors. For instance, the accuracy depends on the errors in a range of systems like, unit measuring unit and angle measuring unit. Next, the accuracy is affected by natural constraints, including angle of incidence in addition to the properties of the road surface, including the colour and brightness of the surface. It is also essential to observe that the choice of the laser scanner greatly depends on time availability, the scenery geometry and the desired accuracy levels. The distance and interval to be measured also play a critical factor. Conclusion It is concluded that road profiling is indeed an essential practice for road builders, government and contractors. This essay maintains that road surface profiling is a critical step in road engineering since it facilitates the collection of micro and macro textures, longitudinal profile and roughness data. The data acquired from road profiling assists the road builders, government and relevant road construction and maintenance authorities to determine the index roughness values and subsequently compute the comfort of ride while on transit. It is further concluded that laser-scanning is a high-tech methodology used by surveyors in profiling of roads. Further, it is upheld that laser-scanning use non-contact lasers that proximate the distance between the surface of the road and the laser scanner’s sensor. It is also observed that using kinematic laser-scanning technology prevents hindrance to traffic flow. Additionally, it is time-saving and guarantees relatively high precision values compared to static measurements. However, a number of shortcoming include the tendency of the laser-scanner’s results to depend on the targets that may shift dynamically, while accuracy of a range of systems concerned with distance-measuring unit and angle-measuring unit. Reference List Acuity 2014, Road Profiling, viewed 13 May 2014, http://www.acuitylaser.com/products/category/road-profiling Grafe, G 2007, “High precision kinematic surveying with laser scanners,” Journal of Applied Geodesy vol. 4 no. 2, pp.185-223 Jean, M & Lars, M 2006, Introduction to Surface Roughness and Scattering, Optical Society of America, Washington, D.C. Parry, I & Marsh, F 2003, “Constructing detailed road surfaces for vehicle dynamics 3D road surface analysis,” Measurement techniques VII, 3-5 PAGOUNIS, V, Tsakiri, M, Palaska, S, Biza, B & Zaloumi, E 2006, 3D Laser Scanning for Road Safety and Accident Reconstruction, viewed 13 May 2014, http://www.fig.net/pub/fig2006/papers/ts38/ts38_03_pagounis_etal_0475.pdf Schulz, T & Steiner, M 2005, Laser scanning and noise reduction applied to Simulation using 3D laser scanning techniques, Transport Research Laboratory. Read More