Photogrammetry and LiDAR are both popular among drone mapping & surveying professionals. But which is the better data collection method?
The truth is each method has strengths and weaknesses which make them ideal for different situations. Thankfully, we’ve gone through what these are and the scenarios they’re most suited to, helping you decide which option is best for you.
What is LiDAR?
LiDAR stands for “Light Detection and Ranging”. LiDAR works by emitting lasers towards the surface of the earth.
More specifically, these ‘lasers’ are pulses of light.
Once these lasers have been emitted, the LiDAR system measures how long it takes for light to be reflected back to it. The time taken for the light to return indicates the exact distance of an object.
This is known as the Time of Flight (ToF) principle.
Using just one laser wouldn’t be very useful for mapping out an area. That’s why many LiDAR sensors are capable of blasting hundreds of thousands of light pulses per second.
These scatter far and wide, so each detail of terrain is hit. This is used to create a 3D LiDAR point cloud, an accurate visual representation of a scanned area’s topography and features.
Think of LiDAR as similar to sonar or radar, which use sound and radio waves to map surfaces and detect objects.
What is Photogrammetry?
Instead of using lasers, photogrammetry uses photos to create 3D models of surveyed areas.
Photogrammetry is the science of making measurements from photographs. A drone-mounted camera will capture multiple overlapping images of the object being modelled. This is so each point can be captured from three positions; its horizontal (x,y) and vertical (z) coordinates.
These images are then stitched together in post-processing software, creating navigable 3D models.
The main difference between LiDAR and Photogrammetry is how they capture data. LiDAR uses lasers & photogrammetry uses photos.
LiDAR is classified as a direct measurement since you’re physically hitting an object with light and measuring the reflection. In contrast, drone photogrammetry is not since it uses images to construct a 3D model.
Photogrammetry results in a full-colour orthomosaic being generated. LiDAR, on the other hand, can only produce a colourised point cloud when combined with a camera.
Beyond these distinctions, there are a few vital areas where the two differ.
LiDAR is, however, a more expensive option when compared to photogrammetry.
If your surveying needs are more general, such that the extra price you pay for LiDAR outweighs the benefit of the additional accuracy boost, photogrammetry is a better option. This is most likely to be the case for broader surveying needs in industries such as construction & mining.
The photo 3D model produced by photogrammetry may make it easier to spot certain features on an object when compared to the point cloud created by LiDAR. This is because the photogrammetry 3D models are stitched together of actual photos rather than an image of multiple points.
Photogrammetry provides you with an affordable, reliable and easy to use option which many teams find easy to integrate into their operations. LiDAR is more complex but can provide you with a more granular level of detail.