With more and more projects relying on geospatial data, laser scanning has become one of the most popular surveying methods. Laser scanning systems, use light pulses to collect information from surfaces. The systems capture millions of 3D coordinates (also known as points), which together form point clouds. The coordinates in a point cloud can create a digital model of the scanned environment.
There are different types of laser scanning technology surveying teams can use, and each type will have different advantages and be more suited to certain projects. Two main types of remote sensing are terrestrial and mobile laser scanning.
Both terrestrial and mobile laser scanning use light pulses to gather information from rural landscapes, urban environments, and human-made structures. However, there are some key differences between these two laser scanning types. Here’s what you need to know about the differences between them so you can choose the right remote sensing method for your project.
What Is Mobile Laser Scanning?
Mobile Laser Scanning, or MLS, is a land surveying method that uses laser systems mounted on moving vehicles. MLS systems can be mounted on land-based vehicles such as cars, trains, and trucks; airborne vehicles such as UAVs and helicopters; or boats. This type of remote sensing surveys landscapes, cityscapes, buildings, and infrastructure corridors, such as railways and roads.
Usually, the traditional surveying process takes a lot of time, interrupts the day-to-day traffic activities, and requires many on-site workers. Mobile laser scanners can reduce the time and money spent on these surveys, freeing up the project budget for other operations and processes.
MLS comes in handy in emergency response situations to analyze ground conditions quickly, as well as for mapping projects like Street View and Google Maps.
What Is Terrestrial Laser Scanning?
Terrestrial laser scanning uses ground-based remote sensing systems. These systems can be mounted on static tripods and scan in all directions, including upwards. Once scans of a single area are complete, the tripod is moved to another location to scan from another angle or capture data from a new area. Static laser scanners often gather data from architectural and engineering structures, building interiors, areas of dense vegetation, mining, and archaeology sites.
Terrestrial laser scanning is also a subtype of MLS. Systems mounted on land-based vehicles are considered both terrestrial and mobile. Mobile terrestrial systems frequently survey road networks, industrial plants, and other large areas.
Mobile Laser Scanning vs Static Terrestrial Laser Scanning
Surveying teams using laser scanning must decide whether to use a static or mobile system. This decision can affect the cost of the project, the amount of time spent gathering data from landscapes and structures, and the quality of the survey data. Here are some factors organizations should consider before choosing a type of laser scanning.
Mobile Systems Can Scan Large Areas Quickly
Mobile laser scanners can survey many miles of land in a short space of time. So for larger projects where teams need to gather point clouds from a large area or a network of transport corridors, MLS might be a better option. Vehicle-mounted systems can make obtaining point clouds a much faster process than it would be with static tripod-mounted systems.
Mobile Laser Scanning Can Survey Areas with Limited Accessibility
While static sensors can scan in all directions, there are still some areas they can’t collect data from — for example, inaccessible areas such as unsafe building sites, areas overrun with vegetation, and overly busy urban areas.
MLS systems can survey areas that aren’t safe or accessible for teams. Airborne LiDAR systems are particularly useful for reaching and collecting data from restricted locations.
Static Scanning Systems Can Produce More Detailed Point Clouds
Static scanning systems typically collect higher-density point clouds than MLS. High-density point clouds have more points (3D coordinates) per square meter. And if you think of point clouds like pixels, the more you have, the clearer the picture.
Stationary systems can produce more detailed and high-density point clouds because the sensor is kept perfectly still throughout the scan. This reduces the risk of point cloud outliers. Static systems can also move so multiple scans can be carried out of a single area from various angles, creating a more accurate and detailed picture of the environment.
It Can Take Longer to Process Files from Static Surveys
With more detail comes larger file sizes, and the larger point cloud files are, the longer they take to process. Using a powerful point cloud processing software will speed up the process, but you can still expect the point cloud registration process to be somewhat lengthier than with MLS data.
Organizations using static scanners must also think about file storage — some point cloud processing software will include cloud storage for large datasets. But if they don’t, you’ll need an impressive amount of digital storage space.
Static Scanning Is a More Affordable Surveying Method
Static scanning is the most affordable type of laser scanning. While MLS can be expensive due to the cost of the vehicle and the vehicle mount, static tripods for scanning systems are affordable and useful for multiple projects.
Airborne laser scanning systems are the most expensive surveying methods, as your organization will need to pay for the hire or purchase of a helicopter or UAV and a pilot.