What is LiDAR?
LiDAR (Light Detection and Ranging) measures distance much like RADAR and SONAR by calculating how long it takes for thousands of laser pulses to reach an object and reflect. These reflections, plus data gathered from other sensors in the LiDAR unit, are then converted into highly accurate (x,y,z) point cloud datasets. The LiDAR unit also includes sensors such as GPS for tracking the location and IMU (inertial measurement unit) to account for the tilt and movement inherent in the drone during flight.
Because LiDAR directly captures depth information, it is widely used where reliable spatial data is required across complex environments. This makes it particularly valuable for infrastructure, terrain mapping, vegetation analysis, and projects where accurate elevation and ground definition are critical.
What is Phodar?
PhoDAR, also referred to as Photogrammetry, involves taking thousands of high-resolution photos over a certain area from different vantage points and overlapping these photos with one point of reference on the ground. Then the series of photographs are used to extract three-dimensional data and create a fully 3D model of the real world.
The datasets from photogrammetry can include both 2D and 3D outputs, along with the texture, shape, and colour of each point or surface. Photogrammetry stitches photos together to create its model, so all the visual features and details of the survey site are available in the 3D model. This is one of the key reasons photogrammetry-derived models often look more true to life than LiDAR outputs when viewed visually.
PhoDAR sits within the broader category of photogrammetry. In practical terms, it is a photo-derived reconstruction method that is often used as a lower-cost alternative to LiDAR for many site mapping and modelling applications.
Differences and Applications of LiDAR and Photogrammetry
Both LiDAR and PhoDAR serve similar purposes, but they have major differences. When determining which technology is best for site surveying, the size of the area, the site conditions, the desired output, and the required level of accuracy all need to be considered.
In short, photogrammetry can cover large areas quickly and can produce highly detailed visual models, while LiDAR is often preferred where more dependable spatial accuracy and terrain penetration are required. Rather than thinking of photogrammetry as simply “low accuracy” and LiDAR as “high accuracy,” it is more accurate to say that each method performs better under different conditions and for different deliverables.
Visually, 3D models acquired from photogrammetry look much closer to real life when compared to LiDAR. This is because photogrammetry preserves the real photographic texture and colour of the site. However, LiDAR can produce higher quality terrain data when vegetation is dense in the site being surveyed. This is because the pulses from LiDAR can penetrate vegetation better, i.e. go around leaves and branches, and map the terrain underneath more effectively than photogrammetry. The higher reliability of LiDAR in densely vegetated areas can be particularly beneficial for projects where vegetation management is important.
If the project at hand allows for flexibility in which technology is used, many would opt for photogrammetry due to the significant difference in cost. PhoDAR is approximately 1/5th the cost of LiDAR. This significant price difference reflects both PhoDAR’s strengths and weaknesses. PhoDAR hardware is cheaper, although the data can take significantly longer to process depending on the size and complexity of the dataset. This makes PhoDAR an attractive option for site maintenance applications, visual site modelling, and broad area mapping where photorealistic outputs are valued.
LiDAR uniquely provides features that are not inherent in PhoDAR and are imperative in many industries. LiDAR can model power lines and cables with significantly higher reliability and accuracy when compared to PhoDAR. Similarly, PhoDAR is well suited to projects such as mapping large areas with varying terrain, quarries, mines, and sites where realistic visual representation is important.
A simple way to distinguish the two is:
- Photogrammetry / PhoDAR is generally best for photo-based visual reconstruction and realistic surface models.
- LiDAR is generally best for robust spatial capture, terrain definition, and complex sites where vegetation or fine linear assets are involved.
Deciphering the Best Choice: LiDAR or PhoDAR?
When it comes to picking the right technology for a project, there is no one-size-fits-all solution. The two technologies’ similarities are like a Venn diagram: both have applications that overlap. However, each technology has features not available in the other. Therefore, understanding which type of data is most suitable for the project is crucial.
The best choice usually comes down to the project objective. If the priority is photorealistic visual output and cost-effective coverage, photogrammetry is often a strong option. If the priority is dependable spatial data, vegetation penetration, or accurate modelling of assets such as powerlines and terrain, LiDAR is often the better solution.
At HIKA Design, we have the full capability to assist our clients in LiDAR data collection. We also excel in working with our network of suppliers to develop technical specifications and conduct purchasing tenders for LiDAR data, ortho-rectified imagery, point clouds, and planimetrics. In addition, we understand where photogrammetry can complement LiDAR to deliver the most practical and cost-effective outcome for each project.