LiDAR surveying is a fast and effective way to capture 3D data. Using laser pulses to calculate distances, capture precise measurements and measure ranges is growing in popularity. This simple way to collect data is accurate, quick, and flexible.
Find out more about LiDAR mapping, and how using light detection and ranging has transformed surveying.
All About LiDAR
It’s ground-breaking mapping technology that takes surveying mobility, accuracy, time-saving and cost-effectiveness to greater heights. That’s how LiDAR was seen when it kick-started most of its development in the early 1960s, shortly after the invention of the laser. The good news is that it has continued to play an essential role in making life easier for engineers and surveyors – and more appealing for CEOs across a wide range of industries.
What’s all the fuss about LiDAR? Well, let’s find out. However, before going into what LiDAR does, let’s start by telling you what LiDAR actually is.
LiDAR is an acronym for Light Detection and Ranging. It’s essentially a remote sensing method that uses rapid light pulses to map out the surface of the earth. It uses the pulse from a laser to collect measurements to create 3D models and maps of objects and environments. In a nutshell, the system calculates how long it takes for beams of light to hit an object or surface and reflect back to the laser scanner. The distance is then calculated using the velocity of light. Depending on the sensor used, LiDAR scanning units can fire hundreds of thousands of pulses per second. Each of these pulsed laser measurements, or returns, can be processed into a 3D visualisation known as a ‘point cloud.’
You can find out more in our detailed article ‘what is LiDAR?’.
LiDAR for Surveying – how does it work?
There are two main types of LiDAR:
Laser-based scanners use a process called trigonometric triangulation to accurately capture a 3D shape as millions of points. A LiDAR instrument works by projecting a laser line or multiple lines onto an object. It then captures its reflection with single or multiple sensors. The sensors are located at a known distance from the laser’s source. As a result, accurate point measurements can then be made by calculating the reflection angle of the laser light.
LiDAR System for Surveying – what are the best use cases?
There are many great use cases for LiDAR. These include civil engineering and surveying, from highways and roadworks, to bridge construction and mapping large retail developments. In fact, LiDAR is extensive, allowing surveying firms to be more cost effective while maintaining the highest level of professionalism. Some great examples include:
LiDAR surveying equipment and 3D scanners help civil engineers get highly accurate results in a very short space of time. Essential when working with tight timeframes.
LiDAR technology is perfect for creating a digital model so you can spot and correct irregularities before building work starts, as well as monitor changes between scans to show progress.
Surveyors prefer LiDAR systems to help them create detailed 3D images, accurate digital terrain models (DTM) and digital elevation models (DEMs) of specific landscapes.
LiDAR really comes into its own when surveying historic sites, occupied spaces, underground environments and dynamic cities.
LiDAR Surveying Benefits – what sets it apart from traditional methods?
LiDAR Drones for Surveying – how surveyors are reaching new highs
Amidst all the new consumer tech developments of the last 10 years, there’s nothing that quite excites forward-thinking surveyors as airborne laser scanning for (drone) remote surveying.
And you can see why:
There are 4 main parts of an airborne LiDAR which produce a vertical accuracy of 15 cm vertically and 40 cm horizontally. It sends over 160,000 pulses per second. This is why LiDAR point clouds create millions of points.
- 1. LiDAR Sensors: As the drone travels, sensors scan the ground from side to side. The pulses are commonly in green or near-infrared bands.
- 2. GPS Receivers: They measure the altitude and location of the drone. These tracks are important for accurate terrain and elevation values.
- 3. Inertial Measurement Units (IMU): As the drone travels, IMUs track its tilt. LiDAR systems use tilt to accurately measure the incident angle of the pulse.
- 4. Data Recorders: As LiDAR scans the surface, a computer records all of the pulse returns. As a result, these recordings get translated into elevation.
LiDAR data attributes can vary, depending upon how the data was collected and processed. You can determine what attributes are available for each LiDAR point by looking at the metadata. All LiDAR data points will have an associated X,Y location and Z (elevation) values.
Most LiDAR data points will have an intensity value, representing the amount of light energy recorded by the sensor.
The real value comes from turning raw data and LiDAR survey data into actionable information. Including being able to georeference your point cloud. With modern software, data that’s been collected can be extracted from most scanner units by either connecting the device to a PC or downloading the data to a USB memory stick. This LiDAR scan data can then be calibrated allowing analysis and modelling. Moreover, LiDAR data processing is very fast. Raw data requires just a few minutes of calibration (5-30min) to generate the final product.
Depending on the environment in which the scan is conducted and the specifics of the 3D laser scanner, an accuracy of 0.002-0.197” may be achieved. This high level of accuracy helps ensure that measurements are correct the first time so that less work is needed to complete subsequent steps in design and production. Additionally, LiDAR takes the human element out of the process making the data even more accurate.
Learn about the accuracy of GeoSLAM’s handheld laser scanners here.
When we look at the overall cost of LiDAR surveys, there are multiple cost items to be considered. First of all, the hardware: UAV LiDAR sensor sets (scanner, IMU, and GNSS) cost anywhere between tens to hundreds of thousands. How much does a drone LiDAR survey cost? It generally turns out to be about £3,000 per km2 for each of the survey grids. On the other hand, for example, GeoSLAM’s ZEB Go mobile laser scanner costs around £22,000. Furthermore, GeoSLAM ZEB products come with a software package and local storage, with no hefty storage or subscriptions costs, making it the most cost effective SLAM system available today.
LiDAR vs Traditional Surveying
We know how time-consuming it can be to set up traditional survey equipment, especially in very inaccessible environments. Fortunately, mobile laser scanners take away all this headache. You can literally create a point cloud as you ‘walk and scan’, or use remote scanning while simultaneously transmitting high-level fidelity images.
Airborne LiDAR helps to create highly accurate digital elevation and terrain models. This makes LiDAR particularly useful for example, in measuring surveying land, tree size, flood elevations, and site distances. Also, for modelling narrow objects such as power lines or road networks and poorly visible objects. All this information is captured in mere minutes – versus weeks when compared to a traditional survey crew using GPS. That means there’s no need to visit the site more than once. In short, with LiDAR you can expect three improvements over a typical survey – faster delivery, value-added service, and a better return on investment.
LiDAR laser technology in surveying has been a game-changer for many companies around the world wanting to take advantage of its many benefits, as you can see from these success stories. And it will continue to do so as the rapid development in LiDAR hardware coupled with advanced, user-friendly software offer professionals greater opportunity to conduct highly accurate surveys faster, safer and more cost-effective.
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