What is LiDAR and how does it work?

TL;DR

LiDAR (Light Detection and Ranging) is a remote sensing technology that uses laser pulses to measure distances and create precise 3D maps of surfaces and environments. A LiDAR sensor emits thousands to millions of laser pulses per second, measures the time it takes for each pulse to return after hitting a surface, and calculates the distance to that surface. By combining millions of these distance measurements with the sensor's known position and orientation, LiDAR creates a dense "point cloud"—a 3D digital representation accurate to within millimetres (terrestrial) or centimetres (airborne). LiDAR is used in mining for stockpile volumes, in construction for topography, in autonomous vehicles for navigation, and in surveying for virtually every spatial data application.

Key Takeaways

• LiDAR works by emitting laser pulses and measuring the time-of-flight or phase shift of the returning signal to calculate distance
• Terrestrial LiDAR (tripod-mounted) achieves 1-3 mm accuracy; airborne and drone LiDAR achieve 2-30 cm accuracy depending on platform
• A single drone LiDAR sensor can emit 100,000-500,000 pulses per second, each returning a distance measurement
• LiDAR can penetrate vegetation canopy to map the ground surface beneath—a capability unique to laser-based sensing
• The global LiDAR market was valued at approximately USD 1.4 billion in 2023 and is projected to reach USD 6.3 billion by 2030 (Grand View Research, 2023)

Table of Contents

• What is LiDAR and how does it work?
  • Definition: what LiDAR means
  • How LiDAR works: step by step
  • Types of LiDAR: terrestrial, airborne, mobile, and drone
  • Time-of-flight vs phase-shift: two measurement methods
  • What is a LiDAR point cloud?
  • LiDAR accuracy: how precise is it?
  • LiDAR applications in mining, construction, and surveying
  • LiDAR vs photogrammetry: which should you use?
  • LiDAR vs radar: what's the difference?
  • LiDAR equipment and costs
  • Frequently asked questions
  • What to do next

Definition: what LiDAR means

Definition: LiDAR (Light Detection and Ranging) is a remote sensing method that uses pulsed laser light to measure distances to the Earth's surface. The sensor emits laser pulses, detects the reflected signal, and calculates distance based on the time taken for the pulse to travel to the target and back. By combining millions of these measurements with precise positioning data, LiDAR creates highly accurate three-dimensional representations of terrain, structures, and objects.

LiDAR is sometimes called "laser scanning" when referring to terrestrial (ground-based) systems. The terms are largely interchangeable, though "LiDAR" more commonly refers to systems that capture large areas from aerial or mobile platforms, while "laser scanning" often refers to tripod-mounted terrestrial systems.

The acronym LiDAR is generally accepted to stand for "Light Detection and Ranging," by analogy with RADAR (Radio Detection and Ranging) and SONAR (Sound Navigation and Ranging).

How LiDAR works: step by step

The LiDAR measurement process follows these steps:

Step 1: Laser pulse emission

The LiDAR sensor emits a short pulse of laser light. High-end systems emit 100,000 to 2,000,000 pulses per second. The laser is typically in the near-infrared spectrum (wavelengths around 905 nm or 1,550 nm), which is invisible to the human eye but highly effective for distance measurement.

Step 2: Pulse travel and surface reflection

The laser pulse travels through the air at the speed of light (approximately 299,792,458 m/s) until it strikes a surface. The surface reflects a portion of the light back toward the sensor. Different surfaces reflect differently—white concrete is highly reflective, black asphalt less so, vegetation partially absorbs the light.

Step 3: Return signal detection

The sensor's detector receives the reflected pulse. The system records the exact time of emission and the exact time of return.

Step 4: Distance calculation

The system calculates distance using the formula:

Distance = (Speed of Light x Time of Flight) / 2

The division by 2 accounts for the round-trip travel of the light pulse.

For a pulse that returns in 67 nanoseconds, the distance is:

(299,792,458 m/s x 0.000000067 s) / 2 = 10.04 metres

Step 5: Position and orientation integration

The LiDAR system combines the measured distance with the known angle of the laser emitter (horizontal and vertical) and the sensor's position and orientation in 3D space. This gives the exact 3D coordinate of the point where the laser struck the surface.

Step 6: Point cloud creation

Millions of these individual measurements are collected and compiled into a point cloud—a dataset containing the 3D coordinates of every point the laser hit.

Types of LiDAR: terrestrial, airborne, mobile, and drone

Terrestrial LiDAR (TLS)

Tripod-mounted scanners used for high-precision industrial work. A TLS unit captures 360-degree data from a fixed position. Multiple positions are combined to cover large areas. Accuracy: 1-3 mm. Used for as-built surveys, plant scanning, and dimensional control.

Airborne LiDAR (ALS)

Mounted on aircraft for large-area mapping. A typical ALS system captures 200,000-1,000,000 points per second across a 1-2 km swath. Accuracy: 10-30 cm vertical. Used for regional DEM creation, forestry canopy analysis, and floodplain mapping.

Drone LiDAR

A LiDAR sensor mounted on a UAV combines the manoeuvrability of a drone with the accuracy of laser measurement. Modern systems like the DJI Zenmuse L2 and YellowScan Explorer capture 200,000-500,000 points per second with RTK positioning accuracy of 2-4 cm. Used for stockpile volumes, cut-and-fill, and topographic surveys.

Mobile LiDAR (MLS)

Vehicle-mounted systems capture data at highway speeds. A single pass can capture a 200 m corridor with 1-5 cm accuracy. Used for road design, rail surveys, and utility corridor mapping.

Time-of-flight vs phase-shift: two measurement methods

LiDAR systems use two fundamentally different approaches to measure distance.

Time-of-flight

A short, intense laser pulse is fired. The system measures the elapsed time until the return pulse is detected. Because light travels so fast, the timing electronics must resolve differences of a few picoseconds (trillionths of a second) to achieve millimetre accuracy. Time-of-flight systems dominate long-range and airborne applications.

Phase-shift

The laser emits a continuous beam modulated at a known frequency. The system compares the phase of the emitted and returned signals. The phase difference is proportional to the distance. Phase-shift systems achieve higher accuracy at short range but cannot measure beyond a certain distance (the "ambiguity interval") without additional techniques.

Most terrestrial laser scanners used in industrial surveying (Leica RTC360, Trimble X7, Faro Focus) use time-of-flight for the long-range capability, with some models using phase-shift for high-resolution close-range modes.

What is a LiDAR point cloud?

The output of every LiDAR survey is a point cloud. A LiDAR point cloud is a dataset where each record contains:

Multiple returns are a unique capability of LiDAR. When a laser pulse hits vegetation, part of the light reflects from the top of the canopy and part continues downward, reflecting from lower branches and eventually the ground. The sensor records these as separate "returns," enabling the creation of bare-earth models beneath forest canopy.

LiDAR accuracy: how precise is it?

LiDAR accuracy depends on the platform, sensor quality, and processing method.

Accuracy is affected by:

• GNSS quality: RTK correction improves accuracy from metres to centimetres
• IMU quality: Higher-grade inertial measurement units reduce orientation error
• Range: Accuracy degrades with distance from the sensor
• Atmospheric conditions: Temperature gradients and humidity affect light speed
• Surface characteristics: Dark, wet, or angled surfaces reduce return signal strength
• Vegetation: Canopy penetration reduces ground point density

LiDAR applications in mining, construction, and surveying

Mining

Construction

Surveying

LiDAR vs photogrammetry: which should you use?

Key point: If your site has vegetation and you need ground-surface topography, LiDAR is the only practical choice. If you need photorealistic visual detail and your site is mostly clear, photogrammetry may be more cost-effective.

LiDAR vs radar: what's the difference?

LiDAR provides the precision needed for engineering applications. Radar provides the range and weather independence needed for aviation, maritime, and military applications.

LiDAR equipment and costs

Terrestrial laser scanners

Drone LiDAR systems

Service costs (Australian rates)

Frequently asked questions

Is LiDAR the same as laser scanning?

Essentially yes, with a terminology distinction. "LiDAR" is the broader term encompassing all laser-based distance measurement systems, including airborne, mobile, and terrestrial. "Laser scanning" typically refers specifically to terrestrial (tripod-mounted) systems used for high-precision engineering and surveying work.

How much does a LiDAR survey cost?

A drone LiDAR survey for a 50-hectare site typically costs AUD 4,000-8,000 in Australia. A terrestrial LiDAR scan of a processing plant section costs AUD 3,000-8,000. Large-scale airborne LiDAR costs AUD 15,000-50,000 per 100 km. Processing and classification add 30-50% to field costs.

Can LiDAR see through walls?

No. LiDAR cannot penetrate solid walls or most building materials. It can penetrate gaps in vegetation (through multiple returns) and some translucent materials like water (to limited depth), but not solid structures.

What is the difference between LiDAR and SLAM?

SLAM (Simultaneous Localisation and Mapping) is a navigation and mapping technique that uses LiDAR (or cameras) to build a map while simultaneously tracking the sensor's position within that map. SLAM systems are typically handheld or backpack-mounted and used in GPS-denied environments like underground mines or building interiors. All SLAM systems use LiDAR (or visual) sensing, but not all LiDAR systems use SLAM.

Does LiDAR work at night?

Yes. LiDAR is an active sensor—it emits its own light—so it works equally well in daylight, darkness, and low-light conditions. This is a significant advantage over photogrammetry, which requires adequate ambient light.

What to do next

LiDAR has moved from specialist technology to standard practice in industrial surveying. If you are managing assets, planning construction, or monitoring environmental conditions, LiDAR provides the most accurate and efficient way to capture spatial data at scale.

1. Define your accuracy requirement. Millimetre precision for engineering work requires terrestrial LiDAR. Centimetre-level topography can be achieved with drone LiDAR.
2. Assess your site conditions. Vegetated sites favour LiDAR over photogrammetry. Indoor or GPS-denied environments favour terrestrial LiDAR or SLAM.
3. Consider your deliverable. Do you need a raw point cloud, a classified dataset, a DEM, or a 3D model? The deliverable determines the processing scope.

Call ISS on 0407 057 015 to discuss your LiDAR survey requirements. We operate terrestrial, drone, and mobile LiDAR systems across Australia and will recommend the right platform and sensor for your specific project.