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What is LiDAR Used For?

February 2024

Airborne LiDAR – Gravity Gradiometry’s Most Under-Utilized Dataset

Conducting LiDAR surveys is one of our service offerings at Metatek. In this insight we discuss what LiDAR is and what LiDAR is used for. If you have any questions or would like more information, make sure you contact our team.

What is LiDAR?

LiDAR (Light Detection and Ranging) data is acquired as a standard element of a Metatek airborne survey. A LiDAR sensor is mounted under an aircraft and generates a laser pulse train. This laser pulse train is transmitted to the surface of the earth and bounces back to the laser. The time taken for it to return is measured and can be used to accurately calculate the distance of the earths surface to the LiDAR sensor, thus determining accurate elevations of points on the ground. These measurements are used to create a map of the area – referred to as a point cloud.

What is LiDAR Used for in Geophysical Surveys

Metatek uses the calibrated, processed and ground-classified point cloud data from the LiDAR sensor to generate a high-resolution Digital Terrain Model (DTM) to remove topography signals from the gravity gradient and scalar gravity datasets.

This alone validates the use of a LiDAR system. LiDAR sensors have the ability to image points that are beneath vegetation; this means trees and other plants will not cause false elevation readings. This is something alternative methods are unable to provide. Therefore, the ground surface derived from the

LiDAR point cloud is more accurate than any other publicly available datasets (such as NASA’s Shuttle Radar Topography Mission (SRTM) data or Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) topography).

LiDAR Beyond Geophysics

Traditionally, this is where LiDAR’s involvement ends for the geophysical survey. 

But what if we went beyond this and investigated other uses for this dataset? What else is LiDAR used for? 

Well, this is one of the new approaches Metatek is taking towards maximizing the use of their acquired data for its clients. A high-resolution ground surface model contains a vast amount of information, and its applications can start to move away from exploration, for example, into urban planning, environmental monitoring, or just a clearer understanding of a region’s topography.

colourised lidar point cloud over urban area showing city infrastructure
Colourised LiDAR Point Cloud over urban area showing city infrastructure

What is LiDAR Used For? Top Applications

Below are five example applications of what a LiDAR-derived DTM can be used for beyond its intended use in a geophysical survey.

1. Enhancement of Aerial or Satellite Imagery

LiDAR can be used to enhance aerial or satellite imagery. Let’s look at a typical satellite image over an area. On its own, it can perhaps tell you there are streams with vegetation, and some topography variations are seen. However, the characteristics of these are difficult to determine from the imagery alone.

However, when the LiDAR DTM is acquired and visually combined with the satellite imagery, previous features are much more defined, and a more complete picture of the terrain is obtained. In particular, the terracing or layering of the topography in the NW corner, which is not immediately apparent in the satellite image. 

This use may initially appear simplistic but can start to become more valuable if, for example, future ground operations are planned in the area.

satellite image
Satellite Image
combined satellite and lidar image
Combined Satellite and LiDAR Image

2. Slope Analysis

So, you have a general idea of the topography from satellite imagery alone and an enhanced view of it when combined with the DTM, but what if you need to know how steep it is?  

Slope analysis can express the steepness of topography in either degrees or percent by calculating a first derivative of the elevation.

LiDAR can be used to generate a slope to map accessible areas and assist in planning ground activities or highlighting areas of potential ground instability. 

slope analysis

3. Aspect

Another use for data collected using airborne LiDAR is determining aspect. Aspect is the directional component of the slope, calculated by comparing the elevation of a grid cell with that of its neighbours. For example, if a neighbouring cell to the east is higher in elevation than one to the west, the centre cell has a west-facing aspect.

This information, used in conjunction with the slope analysis, is vital in any planning of siting structures required to face a certain direction, such as solar or wind farms.


4. Ruggedness

The ruggedness index1 of terrain describes the elevation difference between adjacent cells of the DTM grid.  

At first, it looks like the slope grid, but it is telling more. The lower the index, the smoother the ground, the knowledge of which could aid, for example, the planning of ground seismic activities. Determining the ruggedness of an area is yet another use of LiDAR.

1Riley et al (1999) A terrain ruggedness index that quantifies topographic heterogeneity, Intermountain Journal of Sciences, vol. 5, No. 1-4, pp.23-27.

5. Water Flow Path and Basic Flood Modelling

The DTM generated using LiDAR data can be interrogated to quickly find the low points in the topography and identify them as likely stream/river paths and demarcate watershed and drainage catchments.

 With the stream paths identified, using GIS modelling methods, a predicted rise in water level and a basic flood risk map can be created.

In the further example of flood modelling in an urban environment, the value of knowing where at-risk buildings are, or the way street layout and urban planning influence floodwater movement become more obvious.

water flow path

Final Thoughts on LiDAR and It’s Uses

There are further uses for LiDAR beyond those discussed above. The value of LiDAR data acquired during a gravity gradiometry survey is greatly underestimated outside its “usual” use as a terrain correction.

It’s the most up-to-date high-resolution elevation data over a survey area without having to rely on older datasets, which may not convey any topography changes (such as landslides or man-made alterations). It gives an insight into factors which other disciplines rely on for planning and decision making.

However, one of the strongest arguments for taking LiDAR data further is that no further acquisition cost is needed. This is a dataset which is acquired regardless but underutilized. Until now….

For more information on LiDAR, take a look at our service page. If you have any questions or have an application you would like to discuss, please contact us today. 

dc3t with lidar housing under nose
DC3T with LiDAR housing under nose

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