Light Distance And Ranging (LiDAR) / laser scanning is a comparatively recent technology for capturing unrivaled topography data and accurate measurements of other physical infrastructure. LiDAR became feasible through the availability of lasers with special attributes and various satellite-based positing systems such as the Global Positioning System (GPS). LiDAR has revolutionized the acquisition of digital data for large scale mapping applications and a multitude of other applications where highly accurate data is required.
A typical LiDAR system is operated from a Fixed-Wing Airplane, a Helicopter, a Remotely Piloted Aircraft System (RPAS), and more recently, from Ground-Based Vehicles. The instrument rapidly transmits pulses of infrared light which are reflected off solid objects and back to the sensor. The return pulse is converted from photons to electrical impulses and collected by a high-speed data recorder. Since the formula for the speed of light is well known, time intervals from transmission to collection are easily derived. Time intervals are then converted to distance based on positional information obtained from the systems GPS receivers and blended with the on-board Inertial Measurement Unit (IMU) that constantly records the attitude (pitch, roll, and heading) of the vehicle. LiDAR is an active system, meaning the data can be collected during the day or night. LiDAR systems collect positional (x, y) and elevation (z) data at pre-defined intervals. The resulting LiDAR data is a very dense points cloud. The accuracy of the LiDAR data is a function of the flying height, laser beam diameter (system dependent), the quality of the GPS/IMU data, and post-processing procedures. Accuracies of ±15cm (vertically) can be achieved; with Ground-Based systems being much more accurate again due to the proximity to the targets being scanned.
Transportation agencies are increasingly challenged with the management and tracking of highway assets. LiDAR has become popular among transportation agencies for highway asset management, given its numerous advantages over traditional surveying methods.
Some of the advantages of LiDAR include:
Guard rails, Culverts, Road signage, etc.
Traditional survey methods are often used to document the location of highway infrastructure and signage. However, modern vehicle-mounted LiDAR surveys collect significant amounts of data and provide complete models of the highway, highway condition, as well as all surrounding infrastructure. This data can then be used for a multitude of applications ranging from maintenance to construction, for upgrades, and much more.
Pavement condition monitoring
Pavement condition and performance plays a critical role in the successful operation of the highway network. Up-to-date data on pavement condition are collected by the local and state agencies as a part of the pavement management system (PMS) for decision making and to perform necessary maintenance. The cost of pavement surveying largely depends on the applied methods and survey frequency. LiDAR is preferred for easy collection of highly accurate 3D geospatial information regarding the pavement condition for ensuring flexible, cost-effective, continuous monitoring, and maintenance.
Geometric data extraction and assessment
The geometric design of roads mainly deals with the dimensions and layout of the physical elements of the roadway, following different standards and constraints. The geometric data of a highway is mainly composed of three parts: horizontal alignment, vertical alignment, and cross section. 3D point clouds can be used for the geometric assessment of the highway due to its high data accuracy and density.
Embankment stability monitoring
Embankment stability is an important element of highway maintenance for ensuring safety. It is considered under the design process from the beginning until the implementation of the project. It is mainly influenced by the imposed load, loading pattern, and the condition of the slope. The detailed and accurate information acquired from a LiDAR sensor can be used to assess, characterize, and map the condition of an embankment.
Lane marking and road edge extraction / monitoring.
Lane marking and road edge detection are very important for safe driving. The road edge is the boundary between the road surface and the non-road surface. The lane marking conveys messages to road users regarding the purpose of different parts of the road and where they can legally operate their vehicle. Road edge and lane detection are also necessary for the safe operation of autonomous vehicles. Conventional digital maps with road-level resolution are not sufficient for autonomous vehicles to understand their surroundings. To resolve this issue, LiDAR-based Road edge and lane marking detection systems, mainly based on elevation and reflectivity are becoming popular among transportation agencies and vehicle manufacturers for its higher accuracy and detailed information.
Sight distance assessment
Sight distance is one of the fundamental components of highway design. It is the length of road surface that driver can see at a point along a roadway. Provided sight distance is important to ensure adequate stopping distance at a specified driving speed. If the available sight distance is less than what is required for a driver action, then the risk of a crash is significantly increased. There are four types of sight distance considered in roadway design: intersection sight distance, stopping sight distance, passing sight distance, and decision sight distance. The traditional methods applied for sight distance assessment are often time consuming, cost- and labor-intensive, and require interference with traffic operations to ensure worker safety. Nowadays, many transportation agencies use LiDAR technology for sight distance analysis considering its efficiency over conventional methods.
Urban, city, or town planning is the discipline of land use planning which explores several aspects of the built and social environments of municipalities and communities.
The urban areas in the developing world are under constant pressure of a growing population. Efficient urban information system is a vital pre-requisite for planned development. The increasing demands in urban planning and management sectors call for co-ordinate application of Remote Sensing and Geographic Information System (GIS) for sustainable development of Urban areas. There is an urgent need to adopt Remote Sensing and Geographic Information System approach in urban development and monitoring process for implementing pragmatic plan of Urban development. The plan must incorporate an integrated approach of spatial modeling using Remote Sensing Data, GIS database and GPS solutions.
LiDAR surveying allows Governments, Municipalities, and Townships to create detailed 3D models that can be used for:
According to urban planning firm ACI USA Inc., much of this LiDAR mapping has previously been done by planes flying over areas that need to be surveyed. However, with advances in technology, Vehicle-Mounted (Street-View) LiDAR systems are now available, making the capture of this critical data much more affordable, with better accuracy, and much denser data than traditional methods.
This ground-level approach is currently being adopted for future road evaluation and transportation planning. It is also being used to examine and identify issues with current urban areas or where new buildings and construction are planned. Likewise, this new information is finding its way into GIS applications for the precise location and mapping of critical infrastructure, with these assets being easily classified in rich, highly accurate 3D models.
LiDAR not only allows us to better understand historical sites and buildings, it lets us better understand the cities in which we currently live. By mapping cities in precise detail, ‘digital twins’ can be constructed that allow analysts to understand how we live and build infrastructure that will complement and improve those daily habits.
By mapping cities, civil engineers can capture the information-rich power that 3D scans deliver to construction projects, but on a city-wide level. The impact of new buildings, infrastructure developments and changes to service access can be mapped and modelled, and exact replicas of the city produced — even overlaid with real-time human data delivered by IoT devices.
Fundamentally, LiDAR is the bedrock of the smart city of the future, allowing city planners to gain the data they need to deploy algorithmic analysis and find crucial solutions to accommodate ever-expanding urban populations.
- Urban powerline modeling with vegetation and other encroachment
- Documenting of telecommunications lines and assets
- Strategic planning for military or other special operations
- Disaster management and recovery
Google Earth utilizes 360 Imagery in their street-view feature and is often very useful for exploring new areas.
Likewise, RPM also captures 360 geotagged high resolution imagery while conducting Street-View LiDAR projects. This imagery is very useful for colorizing LiDAR data along with the visualization of features within a project area.
RPM Aerial Services | A division of Canadian Aerial Services Inc. Copyright © 2021 RPM Aerial Services - All Rights Reserved.