"Airborne laser mapping (LiDAR (Light Detection And Ranging) is a fast and reliable method of obtaining 3-dimensional data for the creation of Digital Terrain Models (DTMs)"

Lasermap Image Plus, the parent organization, commenced business in 1997 when it acquired one of Optech's first LiDAR systems. At that time, Lasermap was one of only 11 commercial LiDAR service providers worldwide. Since then, Lasermap has continued to upgrade its equipment and, in 2007, purchased Optech's latest Gemini 167 system With 11 years of LiDAR experience, Lasermap is a premiere provider of LiDAR data collection and production services. A LiDAR system is an active airborne sensor using a laser to measure distances to above ground features and to the ground. The use of LiDAR will produce map accuracies that exceed those specified in the ASPRS standards.

Processing LiDAR Data

During each LiDAR flight, the raw laser data are recorded. At the same time, the GPS and inertial navigation data are also recorded. These two sources provide high accuracy positional information for the system. The GPS and inertial data are processed in tandem to achieve the best positional result. The data are then processed using the proprietary Optech suite of software to produce an ASCII file of (x,y,z) coordinates. Classification of the data is done at the end of the processing cycle. This task processes the data points through an intensive filtering process, and various classes of points are separated. For example, vegetation data can be removed from the ground layer data, and it is also possible to separate buildings and power lines using customized filtering routines.

The data can then be transformed into formats compatible with numerous GIS and CAD software packages.

Using LiDAR To Produce Fast, Accurate, Reliable Digital Terrain Models and Contour maps

An accurate DTM can be used for various types of mapping applications, to produce contours, and for orthorectification of aerial photography.

LiDAR data can be used to produce a detailed DTM in a much shorter time frame than a similar product using any other technology. The LiDAR system emits energy pulses at frequencies of up to 50,000 Hertz - that is 50,000 times per second. These pulses are reflected off the ground, vegetation and man-made structures at different time intervals, allowing the distances between emission and reception to be calculated. Using these distances, along with the attitude of the laser (from the inertial measurement system) and its position (from the GPS), the position and elevation of each spot can be calculated. With the high pulse emission rates, the laser can obtain as many as 3,000,000 3-D points per minute. Depending on the flying height, the aircraft speed, and the frequency and width of the laser scan, the ground point density can be as close as 0.5 meter (2 feet). With Lasermap's state-of-the-art equipment and software and with careful attention to quality control and proper calibration, sufficient data can be collected to produce highly accurate topographic survey maps and/or 3-D models with 0.30 meter (1 ft) contours.

For more information about LiDAR, please review "The Lowdown on LiDAR" and other LiDAR papers by Robert A. Fowler.