In recent years the demand for high-accuracy laser data within the infrastructure sector has increased. The market has discovered the benefits of using both existing off-the-shelf laser data, and ordering new laser data-capture systems suited for high-accuracy planning, building, and maintenance.
“We are not only talking about reduced costs but also about the opportunity to construct secure and more lasting solutions from an accurate geographic source,” says Henrik Åquist, new CEO of Blom Sweden AB.
The challenge of laser data is using the right data for the right purpose. For example, laser data that Blom collects on behalf of Lantmäteriet for its New National High model project can be used for a general study in infrastructure projects. However, for projects demanding accuracy at a centimeter level, data scanned from a helicopter are better suited.
The biggest demand for laser data in infrastructure projects today are in projects related to roads, railroads, harbors, and power lines. Using its TopEye technology for road projects, Blom has been one of the pioneers and major data collectors since the middle of the 1990s.
In those days laser scanning was on a research and testing level. Since then the technology has become standard and is now used in various forms—for example, in road administration projects in conjunction with aerial photos. In railroad projects it is of great importance that data collection can take place without traffic intruding on the busy railroad network.
Power lines are perhaps one of the areas where you can use laser scanning most effectively. Everything from basic planning, surface models, ground models, maps, orthophotos, and visualizing to completing plans for forest maintenance are useful data. Trees near the power lines that are at risk may be detected and valuated, consultants may be engaged for cutting dangerous trees down, and compensation to the land owner can be paid. In Europe, new general directives demand that all power line owners have their lines documented in terms of position of poles and wires. “These demands have put pressure on some of the power line owners,” says Åquist. “However, the demands can be quickly satisfied because a rotor wing system can scan up to 200 km of power line each day.”
Airborne laser scanning has revolutionized the ability to capture highly accurate and expansive ground and surface models, due to its ability to force through vegetation and capture data rapidly.
The accuracy and abundance of detail are due to the number of points collected at a high altitude. When you are talking about laser data that have low point density, you often mean a density between 0.2–2 points/m2. For example, this resolution is suitable for the early stage of road planning, deciding about the road layout, and what consequences that will have on the environment in terms of noise, water flow, etc.
Examples of low point density include comprehensive laser scanning covering whole municipalities from airplanes, or the New National High model.
It can be difficult for clients to know where to use low density laser data if they are unfamiliar with the technology. “In this respect our responsibility as a supplier is crucial,” says Åquist. “A client only needs to know what usage they want from the product, but it is Blom’s responsibility, with our experience from many projects, to decide on which collection method, point density, and flying height is most suitable for the specific project.”
With high density laser data you are generally referring to a point density between 5–50 points/m2. The data are usually captured with a helicopter-mounted system and in most cases, includes simultaneous capture of aerial photos.
Although low-resolution laser data can have a high accuracy, the model has deficiencies because real-world objects between the laser points are not shown. On the other hand, a high-density scan has so little space between the points that all important infrastructure and details can be modeled. For road and railroad projects, height models with accuracy down to 2 cm can be reached.
There are also other applications, such as scanning power lines, that require high point-density data; mapping towers and cables demand high requirements. At the same time, detecting potential trees that threaten to grow or fall onto the line is vital information. In these cases, using laser scanning with low point density and accuracy can have devastating consequences.
High-density laser data can be used to create detailed models of power lines, suitable for 3-D visualizations. The aerial photography, often captured at the same time, is used for detailed inspection of all the parts of the power line, such as isolators and mounting points.
For more information on laser scanning and Blom’s services, contact Dag Solberg at firstname.lastname@example.org.