27 June 2012

Creating Virtual Models with LiDAR

LiDAR (Light Detection and Ranging) is a powerful radar based technology for creating virtual models of physical surfaces and environments . A LiDAR scanner attached to a helicopter, for example, can scan the ground and record information about elevation and ground type, buildings, vegetation, roads, and any other visible structure. Electric utility companies use LiDAR to survey transmission lines remotely, and first responders can use the technology to assess ground conditions after a natural disaster. 

LiDAR works on the same principal of radar, but bounces light off distant surfaces instead of sound.  A closer surface will return a reflection more quickly than a more distant surface, indicating the distance of a reflection's source point from the sensor. The brightness of the reflection indicates what material the laser. is reflecting off of, allowing the sensor to different feature types more easily.

As the LiDAR sensor moves, it precisely calculates its location using GPS, accelerometers, and other motion sensors. As the laser sweeps the surface of interest, the precise location of each point is recorded along the delay and brightness of the reflection.

LiDAR Collection Process
Photo Credit: ©Stratus Aero

This collection of measurements is assembled into a 'point cloud' which can be used recreate virtual models of the surface's 3D features. The differences in the brightness and delay of the laser's reflection indicate information, and this information is organized spatially within the point cloud. False color is used to differentiate different features and objects out of the point cloud data set. As shown in the image below, this false coloration helps the viewer identify distinct features and objects within the point cloud.

False Color Lidar Point Cloud
Photo Credit: Between The Walls

False Color Lidar Point Cloud
Photo Credit: Between The Walls

LiDAR has many practical applications. Utility companies and construction companies use the technology to survey existing or planned pipelines, electrical lines, roads, and buildings. Huge areas of land can be surveyed quickly and in fine detail from the comfort of a helicopter or small plane. Researchers can even use LiDAR to record and model the exact layout of historic buildings, statues, caves, and other culturally important sites. These high resolution 3-D virtual models can be studied by anyone around the world without travel to the site. Additionally, the current condition of the site is preserved, and researchers do not risk further degrading the site by visiting it in person.

LiDAR is a great tool for remotely measuring the physical environment in great detail. It can be used to survey hundreds of miles for a trans-continental pipeline or freeway, or to model indoor areas with a ~3 MM resolution. Ultimately, LiDAR will allow anyone with an internet connection to explore large parts of our world in great detail. 

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.