LiDAR and Geophysical Survey
With BAC’s proven track record in the support of mining and exploration, it was a natural progression into the world of LiDAR, mapping and geophysical survey. With a well-known and well-respected partner, Wooding Geospatial Solutions, who have been mapping Africa for more than 20 years, BAC is very well placed to provide the helicopter service to compliment WGS’s fixed wing operation.
The unrivaled flexibility and utility of the helicopter allows for a much wider range of geophysical mapping and aerial survey services, in any terrain, at any height and at a wide range of speeds.
A Brief Understanding of LiDAR
Light Detection and Ranging (LiDAR), a remote-sensing technique that uses laser light in place of radar, is the latest technology in terrain modeling and Digital Elevation Model (DEM) derivation. From an airborne platform, a laser is directed at a rotating prism that directs the beam towards the ground. The LiDAR unit receives the light reflected back from the ground and uses the time taken for the light to travel from the aircraft to the ground and back to calculate the distance to the surface. The laser sweeps back and forth across the ground in the direction of flight due to the rotation of the prism and coupled with the laser that pulses at around 50’000 times per second, the data captured is vast and extremely accurate. LiDAR units require a high grade Inertial Navigation System (INS) and use both the INS data and the angle of rotation of the prism to calculate the eight for each laser return.
Post Processing Software
Because LiDAR cannot determine what is above ground and what is the surface itself, a post-processing algorithm is required to separate the vegetation, buildings and other above ground features from the actual surface. Highly advanced software analyses the data collected to look for rapid changes in height that are not reasonably expected in a natural surface and, based on size and shape, can class buildings, trees and low vegetation separately. Very dense forest or full sugar cane coverage prevent laser light from reaching the actual ground and are not suited for this type of mapping.
- High Point Density:
Because the laser is a direct measurement over a very small surface area with a very high repeat rate, the resulting DEM is very dense. This density is a requirement for the accuracy of post processing and ensures that even small anomalies on the surface are.
Mapping by direct measurement results in very high accuracy. Each strike is an independent measurement, but because LiDAR cannot see through vegetation, each strike may not be the actual ground. Gaps in vegetation will allow the laser pulse to read the ground between, so, provided the vegetation is not too dense, accurate measurement of the surface can be recorded. The degree of surface accuracy will vary with the amount and type of vegetation and the capability of the post processing software.
- Turnaround Time:
LiDAR is one of the most cost-effective ways of collecting topographical elevation data over large areas. One of the biggest advantages of LiDAR over classic Photogrammetic methods is the speed at which a huge amount of highly accurate data can be measured, processed and delivered to the client. Days of LiDAR survey replace weeks of Photogrammetic observation, and an accurate surface model can be produced within 24 to 48 hours of a survey flight.
Uses for LiDAR Mapping
Mining & Exploration
Road, Rail and Powerline Survey
The Equipment and Aircraft
- Riegl LiDAR System
- SPAN FSAS IMU
- Prosilica 12Mp Colour/Infrared Camera
- Robinson 66 Turbine Helicopter
- Robinson 44 Piston Helicopter
- Cessna 337 Aircraft