Providing an engineering grade measurement of the 3D ground surface is essential in providing a highly accurate terrain correction for our airborne geophysical datasets.
Digital terrain models of both the bare earth and vegatetation cover, used for deriving the final gradiometry products, have value beyond airborne survey for seismic planning, infrastructure mapping, environmental assessment.
LiDAR is an acronym of ‘Light Detection and Ranging’ or ‘Laser Imaging, Detection, and Ranging’. It is a technique for determining ranges (distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be used to create digital 3D models of areas on the Earth’s surface.
Airborne LiDAR is a laser scanner attached to an aircraft during flight, creating a 3D point cloud model of the landscape. This is currently the most detailed and accurate method of creating digital elevation models over large areas. This is particularly useful where there is extensive vegetation cover, especially when tree canopy cover obscures surface morphology.
The resultant LiDAR models have many uses, including:
Accurate terrain corrections for gravity and gravity gradiometry surveys: High-resolution gravity and gravity gradiometry surveys require accurate corrections to remove the effects of the topography and therefore reveal the signal from the sub-surface geology. LiDAR-derived ground elevation models are ideal to achieve this and therefore maximise the value of the survey data. Alternative elevation models (for example, SRTM and other satellite-based techniques) do not give an accurate representation of the ground surface in areas of vegetation and therefore cause errors and add terrain-model noise when used as the basis of a terrain correction.
Geology and Soil Studies: Detection of subtle topographic features such as surface fault expressions, river terraces and channel banks, glacial landforms and the measurements of elevation changes between repeat surveys allow the study of the physical and chemical processes that shape landscapes. Airborne LiDAR surveys can map faults whose surface expressions are obscured by vegetation or are too subtle to be seen by other technology. LiDAR has also been widely used in rock mechanics for rock mass characterisation and slope change detection.
Mining: The calculation of ore volumes is accomplished by periodic (monthly) scanning in areas of ore removal, then comparing surface data to the previous scan.
Biology and conservation: Applications include vegetation coverage estimates, forest canopy height mapping, biomass measurements, and leaf area determination. LiDAR data can also be used to differentiate between tree types.
Renewables: It can an also be used to assist city planners and developers in optimising solar photovoltaic systems by determining appropriate rooftop locations and for determining shading losses.
Access and Infrastructure Planning
The accuracy of LiDAR data allows the rugosity (roughness) of the ground surface to be mapped over large areas. This has played an important role for the planning of ground surveys (seismic, for example), and in the siting of ground-based infrastructure.
