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Documenting a City with Mobile Mapping

Reality Capture Guru
November 2, 2015

Mobile mapping scans

If you’re driving down a city street and notice a car like the one pictured below, you’ve probably spotted mobile mapping and Reality Computing in action.

mobile mapped car

Mobile mapping, also called mobile laser scanning, is a process in which the world around us is captured by laser scanners mounted on a vehicle—typically an automobile of some sort, but also a ship or train, depending on what is being mapped. The resulting point cloud data can then imported into 3D mapping or modeling software to create an existing-conditions map/model to support planning, design, construction, or maintenance efforts.

For example, an existing roadway and surrounding landscape can be digitally captured and used as the starting point for bridge replacement planning. Utility companies can scan above-ground utility lines, poles, and equipment along a city street for maintenance planning or proposed urban development.

Although laser mapping technologies have been around for some years, the price tag for mobile mapping was cost-prohibitive for most project teams. But as laser scanning technology has improved and the price has come down, mobile mapping has become a cost-effective, efficient tool for capturing existing conditions project data, particularly in crowded cityscapes.  And with software such as Autodesk ReCap, these scans can be converted into high-resolution, color point clouds that can be imported into other 3D modeling software for further planning or design. Until recently, documenting or mapping city streets, utilities, and other infrastructure has been a grueling process.

For early design and planning, teams usually just combine a variety of existing mapping data to produce an existing conditions model of a project area. Common data sources include digital elevation models (DEM) of the existing terrain (which are commercially available and based on airborne scanning), aerial orthophoto images, and GIS information that contains property, right-of-way and utility data. This produces a 3D city map with an acceptable level of detail and accuracy for early planning efforts.

But more exact information is needed for detailed design, and this has been the grueling part. In the past, project teams would commission a ground survey of the project area. It is expensive and time-consuming for survey teams (with 4 or 5 of surveyors and technicians) to be constantly setting up and moving their equipment. And think about the traffic on crowded city streets or highways, and the potential safety issues related to those traffic conditions. In addition, they only capture measurements of project-related data. As design progresses, or as the project moves into maintenance/operation phase, the team may need measurements for additional objects, which requires additional surveys.

But now teams can use mobile laser scanning systems to gather more detailed survey information. Scanners mounted on the top of a vehicle drives through traffic and scan the project area. The system in the vehicle includes equipment to calculate and compensate for the vehicle’s location and movement. Most commonly used to capture data from a road, these systems can operate while traveling at highway speeds without exposing workers to traffic or requiring road/lane closures.

Mobile mapping systems allow for efficient and affordable data capture. In addition, they provide design-grade accuracy and can collect a variety of data in one drive by. These systems are transforming the way organizations collect mapping and survey data, and are becoming the ‘new normal’ for data capture along street and rail corridors.

Check out these videos of that have examples of using mobile mapping:

3D data courtesy of TopCon Positioning

 

3D data courtesy of TopCon Positioning

 

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