Laser Scanning
What is it?
A 3-D laser scanner is an advanced type of survey/measurement instrument that is used to remotely measure surface geometry of sites and structures with extraordinary completeness, accuracy and speed.
No special "reflectors" are needed; the instrument measures by analyzing the properties of a portion of the instrument's laser beam energy that is reflected back by any surface. Using a pulse laser beam, the laser "paints" the scene, Measuring the angle and distance to any object and calculating its exact physical location, shape and size.
Unlike traditional surveying tools that are used to record certain, selected points within a scene, a 3-D laser scanner automatically "blankets" the scene with hundreds of thousands or even millions of closely spaced point measurements. By repeating this process across the scene rapidly - over 1000 times/sec - the laser quickly constructs a precise, 3-dimensional model, comprised of millions of measurements, for later use in reconstruction analysis and illustration.
How does it work?
A laser scanner works by using internal motors and mirrors to automatically sweep a narrow laser beam over the scene. Laser scanners are portable and are often mounted on a tripod.
Once a scan has been completed, the instrument is moved to another position on the site to capture parts of the scene not visible from the prior set-up, and so forth. A typical scan may take 5 to 20 minutes; scans are usually done from several different vantage points in order to capture geometry for the entire scene or structure.
Next, the scans are tied together and/or geo-referenced using specialized PC software. Finally, the resulting "registered point clouds" are then used with special software to display, view, extract geometric information and create accurate 3-D models.
Laser Scanning Benefits
The benefits of using Laser scanning are numerous and proven.
- Extremely accurate data:
- Allows confident and in-depth analysis
- Makes admission into evidence easier and less problematic
- Allows analysis of subtle or minute issues, such as roadway slope or vehicle crush
- Allows creation of amazingly realistic and accurate 3-D models
- Large amount of data and coverage area
- Eliminates need to return to site for "one more measurement"
- Eliminates need to determine ALL necessary measurements prior to site visit. Laser captures everything in its sight, so determination of important datums can be done after the fact.
- Allows detailed measurement of ALL data, including small details that may be important in later reconstruction. Traditional "one point at a time" methods require a gross measurement and cannot pick up detailed information about such things as skid marks and debris.
- Rapid data capture
- Reduces time to capture needed data
- Reduces cost to capture data of complex or large scenes
- Reduces time scene must be controlled, if at all
- Remote data capture
- Allows measurement of dangerous conditions or scenes, such as measuring Hi-voltage transmission lines
- Eliminates need to occupy site. Roadway accident scenes can be measured without ever being in traveled way or in dangerous positions
- Allows measurement of scenes and objects that access is not granted to, For instance, a property could be measured in detail from an adjoining parcel; roadways can be measured from the safety of an embankment, over crossing or shoulder.
When we decided to get PSI involved in producing an annimation we had no idea they'd have the impact they would. We were amazed.
Larry Spelling, esq. Wietrab & Wietrab
