Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 3 TYPES OF SURVEY
Appendix 3A-1 shows in general the concept on functioning of the RTK network together with cellular
phone (gsm) communication to obtain the geographical position of a map or engineering feature to
an accuracy of +/- 2 to 3 cm.
3.5 LIDAR (Light Detection and Ranging) Airborne Mapping
Light Detection and Ranging (LIDAR) is an airborne mapping technique which uses Laser to measure
the distance between the aircraft and the terrain of the ground. Airborne LIDAR systems can broadly
be classified into 3 main types: Wide Area Mapping using fixed wing aircrafts, Corridor Mapping
Systems mounted on helicopters and bathymetric mapping systems using either one of these two
airborne platforms.
A typical airborne LIDAR system coupled with a Global Positioning System (GPS) and an Inertial
Navigation System (INS) allow the user to capture geo-referenced “Points” of ground features to
produce highly accurate Digital Elevation Models (DEMs) either day or night in a variety of weather
conditions. The LIDAR system acquires data along a corridor that can be up to 600 metres wide.
These very accurate elevation data have a variety of uses, such as the generation of contour lines,
beach profiles and modeling terrain for 3D applications.
Data acquired using LIDAR systems are often used in conjunction with data from other remote
sensing instruments; including spectral and thermal imaging system and high resolution video and
digital aerial cameras to produce digitally rectified images or orthophotographs. More information on
LIDAR is contained in item 4.17 and Appendix 3A-2.
3-4 March 2009