LiDAR Topography: Optimizing Terrain Mapping with Precision
This article covers LiDAR in the context of capturing topography data. We’ll explain why LiDAR is a game-changer for capturing topography, and describe the different applications and industries benefitting from it. Finally, we’ll cover the different tools and methods to capture LiDAR topography and describe future trends.
Why is LiDAR a Game-Changer for Topography?
A topographic map is a two-dimensional representation of a three-dimensional landscape. It shows both natural and manmade features, such as roads, rivers, lakes, and their names. Elevation is displayed through contours or contour lines, which connect points of equal elevation. Topography maps are used for different purposes, including urban planning, surveying, and resource development.
Topographic maps have traditionally been created using ground-based surveying methods. Land surveys measure the dimensions of a particular area of the earth’s surface, such as horizontal distances, directions, angles, and elevations. This information is used for the production of topographic maps.
LiDAR technology has quickly gained popularity as a data collection method over traditional surveying methods. LiDAR collects large quantities of precise and accurate width, height/depth, and length measurements in a 3D space. These result in detailed 3D point clouds, from which accurate 3D models and maps are created, including Digital Terrain Models (DTMs) and Digital Elevation Models (DEMs). These show the earth’s bare ground topographic surface, without trees, buildings, or any other surface objects. LiDAR technology facilitates such categorizations as individual points are classified based on their real-world representation after they’re captured.
LiDAR has multiple benefits over traditional surveying methods. For example, laser scanners automate the data capture process, eliminating human errors during manual data collection in conventional surveying. Laser scanning technology can cover large areas quickly, thereby outperforming human surveying crews without compromising on data accuracy and reliability.
The benefits of LiDAR for capturing ground topography data are even more profound when combined with drones. From the air, LiDAR sensors collect terrain elevation data from different angles, resulting in more comprehensive and detailed topographic maps than ground-based surveying work. This high flexibility is what makes drone technology and LiDAR such a powerful combination, in addition to enhanced safety and flexibility as it’s no longer required for ground crews to be physically present at a site to capture mapping data. Finally, LiDAR pulses can enter to through small holes between dense canopies and capture information about the terrain structure below it.
Practical Applications of LiDAR in Topography
The precise elevation data of a particular terrain captured with LiDAR technology is used in different industries and applications, including surveying, construction, forestry, utilities, and agriculture.
- Surveying: Drone-based LiDAR allows for quick, safe, and accurate large-area topographical mapping projects. The resulting topographical data and maps are used for a wide range of applications, including updating existing topographical maps for national, regional, and local mapping agencies. Coastal mapping projects combine topographic mapping of the land above the water surface, and bathymetric LiDAR to measure seafloor and riverbed elevations.
- Construction: LiDAR data provides elevation information of an area to help developers to place features such as roads, buildings, and drainage systems. Precise 3D spatial data of the environment helps to properly budget construction projects and avoid delays. The following case study explains how drone LiDAR provides topographic data for the expansion of a theme park.
- Mining: Precise topographic LiDAR data is used in mining for measuring stockpiles, erosion monitoring, and excavation planning.
- Forestry: LiDAR has additional benefits in forestry, as it captures topography data below tree canopy. Elevation data helps forestry managers identify flood risk areas as a risk of intense rainfall or overflooding rivers.
- Utilities: Mapping powerlines is a popular utilities use case. Here, LiDAR drone mapping provides a comprehensive view of vegetation around powerlines, so that it can be trimmed in time to prevent power outages. The accurate topographical 3D data captured with LiDAR drone mapping is also used for planning new powerline installations.
- Agriculture: Agriculturists use LiDAR drone mapping to manage resources better, including optimizing irrigation systems. It allows them to precisely monitor crop health and implement different soil conversation techniques if necessary.
- Urban planning and development: precise topographic data of a terrain’s elevation underlies urban and development projects to extend existing cities
- Disaster management: with more and more unpredictable weather events such as heavy rainfall, topographic data is used for creating hazard maps and related damage assessments in case disaster strikes.
Methods and Tools for LiDAR Topography
LiDAR Topography methods
LiDAR topography is captured from the ground or the air. When captured from the ground, a choice is made between static or mobile scanning. When data is captured from the air, a manned aerial vehicle or smaller, unmanned drone is used. For both methods, a combination of LiDAR sensors and additional hardware and software ensures high-accuracy and reliable topography data.
LiDAR Topography tools
Here’s a quick rundown of the different tools for capturing LiDAR topography:
- Platform: LiDAR sensors are used in combination with a platform to mount the sensor. LiDAR topography data is captured in the field with LiDAR sensors of choice. This can be a terrestrial, static LiDAR scanner if the data is captured on the ground. A mobile LiDAR scanner uses a moving platform, such as a car or van.
Drones or manned aerial vehicles capture LiDAR topography from the air. Different types of drones are available, including fixed-wing, single and multi-rotor options. For large-scale topography projects, a fixed-wing allows for heavier payloads with higher-quality sensors and cameras.
- Payload: LiDAR is captured with integrated sensors in a single device, the LiDAR scanner. This is usually part of a larger, multi-component payload which is mounted on a platform of choice when data is captured with a moving platform or from the air. Often, a multi-sensor payload is used for a single job which includes cameras, a GPS receiver, and IMU (Inertial Measurement Unit). For high-accuracy and reliable data, a GPS receiver and IMU are required to help track the drone or aerial vehicle’s location and motion at all times, so the correct location information is tagged to each measurement.
- Drone flight planning software: When flying a drone autonomously, a pre-planned flight plan is usually made with a flight planning application of choice. This ensures the entire area of interest is covered while the most optimal flight path is followed to optimize the drone’s battery power.
- Ground control points: These are strategically placed and well-visible markers on the ground that help to improve the accuracy and reliability of the topography data when captured from the air. These points are measured independently so their location is known and functions as a spatial reference for the captured LiDAR data.
- Post-processing software: this is special software for improving the accuracy of the 3D point data. It is used often in combination with placing ground control points in the area where the data is captured.
Challenges and Limitations of LiDAR in Topography
Although LiDAR has many advantages, there are some limitations and challenges when capturing and processing 3D point clouds:
- Visual limitations: Man-made structures such as bridges or buildings can occlude the surface below when capturing LiDAR from the air. This may require ground-based data acquisition methods to make up for missing data.
- Limited color information: Without an additional RGB camera capturing photogrammetric imagery of a scene, LiDAR data contains no color information. This may limit data interpretation.
- Weather conditions: LiDAR does not function well in adverse weather conditions, including rain, fog, or snow.
- Large data quantities: Large files of point cloud data need require processing before 3D models and maps are created.
- Reflectance: LiDAR measurements are negatively impacted in bright sunlight if there’s a lot of reflectivity from a surface, such as a river or lake.
Emerging Trends in LiDAR Topography
Advancing technology changes how LiDAR topography is captured and processed. Here are some of the emerging trends in LiDAR topography:
- More options for larger payloads: Increasingly, drones can spend more time flying with a single battery and carry heavier payloads, thereby covering larger areas. This makes them more efficient for large-scale topography mapping projects.
- Better flight planning software: Drone flight planning software is improving to the point it can take maximum advantage of all the sensor capabilities, resulting in better data and more efficiency per flight.
- AI and Machine Learning integration: Automated feature extraction and data processing require less human intervention without compromising on data accuracy.
- Real-time data processing: with the latest 5G technology, data is processed right when it is being captured, resulting in faster project turnaround times.
Frequently Asked Questions
What makes LiDAR better than traditional methods for topography?
LiDAR captures precise and accurate topographic data more safely, efficiently, and faster than traditional surveying methods. It is also a more scalable solution for large-area mapping projects.
Can LiDAR be used for small-scale topographic projects?
Yes, LiDAR is a great option for small-scale topographic projects. Drone-based LiDAR in particular is easy and quick to deploy, making it an efficient solution for small-scale projects.
What industries benefit the most from LiDAR topography?
Surveying and construction benefit the most from LiDAR topography, as any project involving building new structures requires the collection and mapping of precise elevation data to minimize risk and properly plan its location.
