Posted on February 24, 2023 in Help and UAV LiDAR
Our Frequently Asked Questions give you more in-depth information about LiDAR and UAV LiDAR – how it works and when you would use it. If you have a question we’ve not covered please do get in touch.
- What do all these geospatial and LiDAR terms mean?
- What is LiDAR?
- What is UAV LiDAR?
- How does UAV LiDAR work?
- What is the difference between a LiDAR sensor and an integrated UAV LiDAR system?
- When would I choose UAV LiDAR over UAV photogrammetry?
- Is drone LiDAR more accurate than drone photogrammetry?
- How does LiDAR penetrate through vegetation and trees?
- Can vegetation be too dense to penetrate?
- How accurate is drone LiDAR?
- How much does UAV LiDAR cost?
- What applications is UAV LiDAR useful for?
- How is UAV LiDAR used in survey and mapping?
- How is UAV LiDAR used in forestry?
- How is UAV LiDAR used for environmental applications?
- How is UAV LiDAR used in research?
- How is UAV LiDAR used in utilities?
- How is UAV LiDAR used in archaeology?
- Can I use a UAV LiDAR system in a building or underground?
- Does UAV LiDAR work in the rain, fog or snow?
- Can UAV LiDAR systems penetrate through water to map the seabed or a river bed?
- Can I use my LiDAR system at night?
- Which drones does Routescene recommend to fly a UAV LiDAR System?
- What is the difference between range and flying altitude?
- Can I collect LiDAR and photogrammetry data together?
- What is GNSS?
- What is RTK and how is it different to PPK?
- What is INS?
- What is the difference between absolute accuracy and relative accuracy?
1. What do all these geospatial and LiDAR terms mean?
To help you understand geospatial, UAV LiDAR and data processing language here’s a glossary of commonly used terms.
2. What is LiDAR?
Light Detection and Ranging or LiDAR sensors use lasers to determine the distance from the sensor to an object. LiDAR sensors typically have multiple laser channels which enable millions of points per second to be collected and converted into a point cloud. The point cloud creates a 3D view of the real world, the term “digital twin” is often used. LiDAR is a remote sensing technology which means that you do not need make physical contact or be close to the object being mapped. This is hugely beneficial if there are Health & Safety issues to consider.
What is UAV LiDAR: Read the full article.
3. What is UAV LiDAR?
LiDAR data is acquired using a variety of platforms such as Unmanned Aerial Vehicles (UAVs), airplanes, cars, backpacks or by using static terrestrial laser scanners. A UAV or drone is an aircraft without a human pilot, crew, or passengers on board.
When a UAV carries a LiDAR system and is used to capture data about the surroundings, the term UAV LiDAR (or drone LiDAR) is used.
What is UAV LiDAR: Read the full article.
4. How does UAV LiDAR work?
UAV LiDAR uses an integrated system of different sensors that enables the terrain below the flying drone to be scanned. At the same time as collecting the LiDAR scan data a very accurate position and orientation of the LiDAR sensor is recorded to enable the LiDAR scans to be “geo-referenced” into a point cloud.
5. What is the difference between a LiDAR sensor and an integrated UAV LiDAR system?
UAV LiDAR is more than just using a LiDAR sensor and a drone: an integrated UAV LiDAR system is needed to capture high quality 3D data. A UAV LiDAR system consists of a LiDAR sensor, a GNSS\INS sensor, a recording system, radio telemetry for real-time monitoring of the sensors and a hardware connection between the LiDAR and the GNSS\INS sensor. The latter is required to ensure that synchronisation between the two is accurate to less than a millisecond.
6. When would I choose UAV LiDAR over UAV photogrammetry?
This depends on your application and the final output you need.
LiDAR is a remote sensing technology using lasers to measure the distance to a surface or to sense objects. Photogrammetry is a technique to capture high-resolution photographs to recreate a survey area.
If you’re surveying land with vegetation coverage and you need to create a Digital Terrain Model (DTM) then LiDAR is the best technique. If you need to capture the layers of vegetation, through a woodland or forest, the laser pulses from the LiDAR can penetrate between branches and leaves to yield a high vertical accuracy from the canopy to the ground. LiDAR can also be used in low light conditions or during the night.
If you require a Digital Surface Model (DSM), or the site you are surveying does not have vegetation cover, or you require a fine level of detail of surfaces and features, photogrammetry is the better option. Photogrammetry needs to be undertaken in good light conditions and care needs to be taken if working with areas with shadows.
7. Is drone LiDAR more accurate than drone photogrammetry?
This depends on your application and the level of accuracy you require.
Done correctly, both UAV LiDAR and photogrammetry are reliable and accurate methods. Your end results will depend on the specification of your LiDAR system or your photogrammetry system (drone and camera).
8. How does LiDAR penetrate through vegetation and trees?
Laser pulses emitted from a LiDAR system penetrate through the gaps between branches and leaves, reflecting from objects both on and above the ground surface.
What is UAV LiDAR: Read the full article.
9. Can vegetation be too dense to penetrate?
This depends on your choice of UAV LiDAR System. Generally the higher the number of lasers in your UAV LiDAR System the better its’ vegetation penetration capability.
Useful link: Routescene UAV LiDAR Systems specifications
10. How accurate is drone LiDAR?
This depends on the specification of your UAV LiDAR System and your survey planning. The accuracy of the overall system depends on a variety of factors including the LiDAR sensor, the GNSS / INS system, if you have a single or dual antenna heading solution, and the option to post-process the drone trajectory. Your survey planning including whether you establish Ground Control using Targets and your accepted level of Quality Control will impact on accuracy, as will your drone flying altitude and speed.
Useful links:
The fundamentals of LiDAR accuracy explained
Improving UAV LiDAR survey accuracy using Ground Control Targets
Routescene UAV LiDAR Systems specifications
11. How much does UAV LiDAR cost?
Entry-level drone LiDAR systems start at around $23,000 (USD) however as with everything you get what you pay for. Low cost options are great for learning however they compromise on quality and hence the quality of the results. If you are starting out and do not need a high level of accuracy nor high resolution then this may be for you.
If you require a commercially reliable UAV LiDAR system with Quality Assurance embedded into the hardware and the software then your choices start from around $50,000 (USD).
Useful link: Routescene UAV LiDAR Systems
12. What applications is UAV LiDAR useful for?
UAV LiDAR is well suited for:
- Survey and mapping and research, particularly in forestry, environmental and archaeological applications due to its superb capability to penetrate through vegetation to deliver high resolution Digital Terrain Models (DTMs)
- Hazardous environments such as landslides, steep or difficult terrain, quarries and open mines
- Vegetation management and corridor mapping in the utilities sector.
Useful link: Applications suited to UAV LiDAR
13. How is UAV LiDAR used in survey and mapping?
All survey and mapping projects including planning and development of the built environment, mining and quarrying, digital twins.
Useful link: UAV LiDAR uses in Survey & Mapping
Case study: Tree preservation on potential building site
14. How is UAV LiDAR used in forestry?
For forestry management, planning, maintenance, forest fires, carbon capture and research.
Useful links:
UAV LiDAR uses in Forestry
Case study: UAV LiDAR transforming operational forest management
Case study: UAV LiDAR used to manage woodland against disease
15. How is UAV LiDAR used for environmental applications?
Land management activities including conservation, maintenance, coastal and river erosion, inland waterways and research.
Useful links:
UAV LiDAR uses in Environmental
Case study: UAV LiDAR used to monitor landslides
Case study: UAV LiDAR used to reveal radiation hotspots at Chernobyl
16. How is UAV LiDAR used in research?
LiDAR is used across a multitude of research projects from environmental and climate change research to archaeological research.
Useful link: UAV LiDAR uses in Research
Case study: Mapping the arctic tundra to inform global climate modelling
Case study: Forest canopy structure characterization to assist carbon reduction policies
Case study: Assessing vegetation to understand the characteristics of forest fires
17. How is UAV LiDAR used in utilities?
Vegetation management and corridor mapping for power lines, overland pipelines and other utilities assets.
Useful link: UAV LiDAR uses in Utilities
Case study: Powerline vegetation management to prevent outages
Case study: Mobile and drone LiDAR mapping used to plan upgrade of powerlines
18. How is UAV LiDAR used in archaeology?
Examples include forensic archaeology, cultural heritage and national interest, preservation.
Useful link: UAV LiDAR uses in Archaeology
Case study: UAV LiDAR used to locate WWII prison camp in UK
Case study: UAV LiDAR used to identify ancient structures at ancestral Pueblo site, USA
19. Can I use a UAV LiDAR system in a building or underground?
Flying drones indoors presents a sizeable health and safety issue and is not usually recommended. It does depend on the building and how restricted the space is. Mounting your UAV LiDAR system in a different way rather than on a drone is an alternative e.g. a robot or cart.
In GPS-denied environments such as indoors and underground mines you will need to consider object detection and SLAM algorithms.
20. Does UAV LiDAR work in the rain, fog or snow?
The best weather to operate UAV LiDAR Systems in are dry, calm conditions.
The Routescene UAV LiDAR Systems are able to withstand a light rain shower; the LiDAR scanners within the LidarPod options are rated to IP67; the LidarPod has IP68 rated connectors and rubber seals to ensure no water ingress.
21. Can UAV LiDAR systems penetrate through water to map the seabed or a river bed?
There are different types of LiDAR. The LiDAR used in most UAV LiDAR systems is to perform airborne topographic surveying. For mapping the seabed or a river bed you will need to use a Bathymetric LiDAR system. This uses a different LiDAR wavelength which is able to penetrate water. The conditions for using Bathymetric LiDAR to map the seabed are very specific so it might be more suitable to use a conventional echosounder to undertake the survey.
22. Can I use my LiDAR system at night?
LiDAR is not affected by daylight and can be used day or night. Obviously when using a LiDAR system on a drone for safety you will be limited to flying in daylight hours. For mobile mapping you can use a LiDAR system in both the day and night.
23. Which drones does Routescene recommend to fly a UAV LiDAR System?
This depends on a number of factors including payload, flight performance (duration and speed), fuel type, type of drone (multicopter, Vertical Take Off and Landing (VTOL), helicopter or fixed wing), and if you need Beyond Visual Line of Sight (BVLOS) operations for your surveys.
Useful links:
Considerations when choosing a drone platform for LiDAR
Routescene UAV LiDAR Systems: Mechanical and electrical drone integration and heading
24. What is the difference between range and flying altitude?
These two are very different parameters and both will impact on your survey planning:
- Range refers to the distance between the LiDAR sensor and an object.
- Flying altitude refers to the height above the ground at which an aircraft / drone flies commonly referred to as AGL (Above Ground Level).
At a certain flying altitude the LiDAR sensor will map the ground below in relation to its maximum range. Consider a triangle where the drone is at the top of the triangle, the two sides are equal to the Maximum range of the LiDAR sensor and the base of the triangle is known as the Swathe. The swathe is the strip of ground that is mapped in a single pass.
Useful link: Routescene UAV LiDAR Systems specifications
25. Can I collect LiDAR and photogrammetry data together?
Yes. In theory you would plan 2 flights: to fly LiDAR at as low an altitude as possible and slower to gain as high a resolution as possible, then photogrammetry at a higher altitude.
In practice of course it depends what your application is and the result you need to achieve. Many UAV LiDAR Systems give you the option to fly with and without cameras to collect LiDAR and photogrammetry at the same time.
26. What is GNSS?
GNSS stands for Global Navigation Satellite System. GNSS consists of several different constellation of satellites (GPS, Gallileo, Glonass, Beidou) which can all work together to transmit positioning and timing information to a ground based GNSS receiver. This information is then used to determine the absolute position of the GNSS receiver on the earth’s surface.
Here’s a glossary of commonly used geospatial, UAV survey, LiDAR and data processing terms.
27. What is RTK and how is it different to PPK?
RTK is short for Real Time Kinematic and it is a technique used in real time to enhance the precision of position data using carrier-based ranging i.e. you correct your location data as you are collecting it.
PPK is short for Post-Processed Kinematic and it is a technique used in post-processing to enhance the precision of position data using carrier-based ranging i.e. you correct location data after it is collected and uploaded into your post-processing software.
Here’s a glossary of commonly used geospatial, UAV survey, LiDAR and data processing terms.
28. What is INS?
An Inertial Navigation System (INS) is an sensor consisting of a set of 3 gyros and 3 accelerometers which all work together to determine the 3D velocity and absolute orientation of the sensor. An INS is used together with a GNSS receiver to provide high accuracy position and orientation information to enable LiDAR scans to be corrected for motion of the drone.
29. What is the difference between absolute accuracy and relative accuracy?
Accuracy can be defined as how close a measurement is to its real value.
Absolute accuracy is defined as the difference between the position of a point in a 3D model to its true real-world position. Absolute accuracy takes into consideration the coordinate system in use, the transformation parameters, and the errors present in the reference base station.
Relative accuracy is defined as a measure of positional consistency between a data point and other near data points in a 3D model i.e. relative to each other.
For any survey you will always be able to determine relative accuracy, and if additionally, your survey data needs to be analyzed against other datasets then absolute accuracy will be required.
Useful links:
The fundamentals of LiDAR accuracy explained.
To help you understand UAV LiDAR and data processing language, here’s a glossary of commonly used geospatial, UAV survey, LiDAR and data processing terms.