Wide-area, sub-decimetre positioning for airborne LiDAR surveys using CORSnet-NSW

Airborne LiDAR surveys produce high-resolution, very accurate surface elevation models which are used for many applications in surveying and civil engineering, as well as for flood prevention and mitigation, monitoring coastal erosion and land subsidence, etc. The key to producing high quality elevation products is very precise geolocation and orientation (or “georeferencing”) of the LiDAR instrument at the times when the measurements are made, obtained with a combination of on-board GNSS and inertial sensors. The usual practice is to deploy reference GPS/GNSS land receivers in the area where the aircraft will be flying, and to obtain a precise trajectory by means of the short-baseline differential GNSS technique. This could mean installing and operating receivers at many sites during a flight mission if the area surveyed is a large one. In this paper, an example of an alternative approach will be presented: using as reference receivers those of a sparse network of Continuously Operating Reference Stations (CORS) in New South Wales known as CORSnet-NSW, and a wide-area GNSS technique for obtaining the aircraft trajectory with sub-decimetre accuracy even with baseline lengths of several hundred kilometres. This may be comparable in precision and accuracy to the short-baseline method, but without the cost and logistical complications of having to deploy and operate one’s own reference receivers during a mapping mission. This opens up a new level of operational capability allowing flexibility for weather conditions and priority response applications. The paper will be illustrated with the results of tests organised and conducted by the NSW Government’s Land and Property Management Authority, in collaboration with the University of New South Wales, in June 2009.