Get detailed information on choosing LiDAR or photogrammetry for 3D mapping and surveying from your UAV. Also, know when you should use them both? And check which one is the best, Drone LiDAR or Photogrammetry?

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A Technical Guide
Drone LiDAR Vs. Photogrammetry

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Introduction
• GIS (Geographic Information System) is gaining momentum in the present
scenario. Photogrammetry& LiDAR (Light Detection And Ranging) technologies are
latest technologies revolutionizing the way we are working. In this article, let us dig
through the circumstances to determine the right kind of sensors to use.
• UAVs (Unmanned Aerial Vehicle) promises cheap and easy survey’s, but yes, there is
something more that they can provide. To get the results that suit your requirements,
you probably have to educate yourself about the sensors the UAVs uses to capture the
data. You will also have to educate yourself about LiDAR and Photogrammetry.
• Here is an informative guide that takes you on a deep dive to decide when it is best to
use photogrammetry, LiDAR, or both when you are surveying with your UAV.

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Apply UAV LiDAR when…
• You want to map below the tree shade, mine sites conveyors and other various
obstructions.
• Reason: Photogrammetry faces difficulty while generating elevation models in
areas where objects block the ground. The traditional photogrammetry tends
to do mistake while creating a digital elevation map. When calculating
elevation for a point on the earth, Photogrammetry requires two images that
can see that point. If a tree is interfering the position, it may show up in one
picture but not the other. It probably confuses the automation algorithms that
match the images. As a result, the output is a noisy elevation model.

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What’s the scenario of Modern Photogrammetry?
• Well, it worsens the problem. Once the algorithm is developed,
photogrammetry could generate “very dense point clouds, which are
often with a spacing factor or two or are larger than the resolution
images.” This is called as Dense Image Matching (DIM) which creates
surface models rather than actual elevation maps.
In other words, Photogrammetry is not an ideal technology for mapping
elevations when the ground isn’t clear from all angles.

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Apply UAV LiDAR When…
• You are modeling smaller, narrow objects like pipes, sharp-edged features (roof
edges), and field of rocks.
Reason: LiDAR Models the object excellently because a single ray from the
scanner measures each point in the cloud. Whereas, in Photogrammetry, the
model doesn’t correspond to the object as well as modern photogrammetry
makes rough estimations and then smooth’s the model out to remove noise.
Thus, this makes modern photogrammetry a tough sell for modeling the tinier
objects precisely.
Now let’s have a look at when to use Photogrammetry.

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Apply UAV Photogrammetry when…
• You are imaging bare earth mine sites, groundwork projects, other areas
that are not occupied by trees as well as buildings.
Reason: Drones are indeed cheaper, lighter as well as faster in working. If
the work you want to do doesn’t require LiDAR, then attaching a camera
to your UAV will save a lot of money and time as well.

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Apply UAV Photogrammetry when…
• You are performing a small mapping project, and photogrammetry data
will fulfill your requirements.
Reason: It is financially not feasible to mobilize a manned aircraft for a
small-site mapping project work. Whereas, a UAV is small to handle by a
single surveyor and operate it in the field without any help.

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Apply LiDAR as well Photogrammetry when…
• You are about to perform modeling that requires LiDAR.
Reason: The high-resolution data can be a bit tough to collect with aerial
LiDAR. This means one needs something extra to get the data with
imagery. The ideal scenario is to use imagery for context and LiDAR for
obtaining the 3D Component.
While the cameras are inexpensive and offer a great value that there
aren’t many facts to ignore them out of the UAV sensor package.

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Use What Makes Sense For Your Business
• LiDAR and Photogrammetry are both impactful and full of potential when
utilizing in right way. The point is finding the right sensor for your
requirement.
In a more straightforward form, if you want to map clean stockpile yards
of fine materials, then photogrammetry is the cost-effective solution. On
the other hand, for the projects that require modeling, then LiDAR is a
perfect choice.

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The beginning of the new era of 3D Scanning (Solid-State LiDAR)
• Well, the technology will see a sharp shift in coming years. The reason is Focal
Plane Array (FPA) LiDAR also known as Flash LiDAR or Solid-State LiDAR.
Here is the easiest way to understand how FPA works. Imagine it as a digital
camera taking pictures. Once LiDAR frames a shot, instead of taking pictures, a
single laser flash and the entire scene gets captured by an array of detectors.
• The FPA LiDARs are perfect for drones because they are cheaper, smaller as
well as lighter and are more geometrically exact than the existing LiDAR units.
Thus, the demand for FPA LiDARs is going to skyrocket in the next few years.
Stay tuned till then!