Surveying has always been about understanding land. Thousands of years ago, Egyptians used ropes and rods to mark boundaries for farming and taxation. Today, South African surveyors are using advanced technology like lasers, drones and 3D mapping software to capture land with remarkable accuracy. Two of the most important tools are LiDAR and photogrammetry. But what exactly are they, and when should each be used?
- What Is LiDAR?
- What Is Photogrammetry?
- When to Use LiDAR
- When to Use Photogrammetry
- Using Both Together
- In Summary
What Is LiDAR?
LiDAR stands for Light Detection and Ranging. It works by sending thousands of laser pulses per second from a sensor, often mounted on a drone, aircraft or ground unit. These pulses hit the surface and bounce back to the sensor, allowing the exact distance to be calculated.
The result is a point cloud, which is a highly detailed 3D model of the environment. Because LiDAR can penetrate vegetation and works in low light, it is ideal for topographic mapping, flood modelling, forestry, mining and other projects where accuracy is essential.
Types of LiDAR Surveys
LiDAR surveys can be carried out in different ways, depending on the project:
- Aerial LiDAR, mounted on planes, helicopters or drones, covers large areas quickly
- Terrestrial LiDAR, using tripod-mounted scanners or mobile solutions, captures detail from the ground
- Wearable or mobile LiDAR, powered by SLAM technology, allows surveyors to collect data at walking speed, even inside buildings or in tight spaces
Benefits of LiDAR Surveys
Some of the main benefits of LiDAR include:
- High precision and accuracy
- Rapid data collection over large areas
- Ability to work in dense vegetation or low-light conditions
- Safer surveying in hazardous or hard-to-reach environments
Deliverables often include Digital Elevation Models (DEMs), Digital Terrain Models (DTMs) and 3D CAD maps, all of which are essential for engineers, planners and developers.
What Is Photogrammetry?
Photogrammetry is a different technique that uses overlapping photos to create 3D models. Specialised software stitches these photos together using triangulation, producing a model that includes both shape and texture.
The strength of photogrammetry lies in its photo-realistic results. It is often more cost-effective than LiDAR and works well for smaller sites where visual detail is just as important as measurement accuracy.
Types of Photogrammetry
Photogrammetry is generally divided into two main categories, depending on how and where the images are captured:
1. Aerial Photogrammetry
- Photos are taken from planes, helicopters, or drones.
- Ideal for mapping large areas, creating topographic maps, and producing 3D terrain models.
- Commonly used in land development, agriculture, forestry, mining, and urban planning.
2. Terrestrial (or Close-Range) Photogrammetry
- Photos are taken from ground level using handheld or tripod-mounted cameras.
- Useful for detailed measurements of buildings, construction sites, cultural heritage sites, or smaller landscapes.
- Often used in architecture, archaeology, and structural monitoring.
Benefits of Photogrammetry
Photogrammetry has a wide range of benefits, especially when compared with traditional surveying methods:
- Requires less specialised equipment than LiDAR and often uses standard cameras
- Produces detailed, photo-realistic 3D models and orthophotos.
- Can be applied to projects of all sizes, from small buildings to large landscapes.
- Drones and aerial surveys can capture large areas quickly with minimal fieldwork.
- Uses widely available equipment and software, making it suitable for many industries.
- The realistic imagery is easy to interpret for planners, architects, and stakeholders who may not be familiar with technical survey drawings.
When to Use LiDAR
LiDAR is best suited to projects where:
- Precise elevation data is needed
- The site has heavy vegetation or varied terrain
- Large areas need to be covered efficiently
- Accuracy matters more than visual appearance
When to Use Photogrammetry
Photogrammetry is best suited to projects where:
- Photo-realistic visuals are important
- The site is open, clear and well-lit
- Budget is limited
- Smaller, detailed sites need to be captured
Using Both Together
In many projects, the best approach is to use LiDAR and photogrammetry together. LiDAR provides the structural framework of terrain and elevation, while photogrammetry adds realistic texture. This combination is increasingly common in construction, archaeology, city planning and asset management.
| Feature | LiDAR | Photogrammetry |
|---|---|---|
| Technology | Uses laser pulses to measure distances and create point clouds | Uses overlapping photos to create 3D models through triangulation |
| Accuracy | Very high accuracy, even under dense vegetation | High positional accuracy, but less precise in heavily covered areas |
| Data Output | Point clouds, Digital Elevation Models (DEMs), Digital Terrain Models (DTMs) | Textured 3D models, orthophotos, photorealistic maps |
| Best Conditions | Works in any light, including night, and penetrates vegetation | Requires good lighting and clear visibility |
| Visual Detail | Provides structural detail but less visual texture | Produces highly realistic, photo-textured models |
| Equipment | Specialised LiDAR sensors (drone, plane, vehicle, or tripod mounted) | Standard cameras or drones with high-resolution cameras |
| Cost | More expensive due to equipment and processing | More affordable and accessible |
| Speed | Fast data collection over large areas | Quick setup and capture for small to medium sites |
| Applications | Topographic mapping, flood modelling, forestry, mining, infrastructure | Architecture, cultural heritage, construction monitoring, visual presentations |
| Best Used For | Projects needing precision elevation data, large or vegetated areas | Projects needing photorealistic visuals and lower-cost surveys |
In Summary
LiDAR and photogrammetry are powerful tools that have transformed the way we survey land in South Africa. LiDAR offers accuracy and depth, while photogrammetry delivers visual detail at a lower cost. The right choice depends on the project, and often the most effective solution is to use both together.
Whether you are developing land, managing resources or planning infrastructure, S.J. McMillan Surveys can help you with your surveying needs. Contact us to discuss your project and how our team can assist.
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