How Does Photogrammetry Work? Updates in the Age of the Drone

July 31, 2023 By Analytikal9gmail-com
Drone Surveying

Technological advancements have changed much of modern life — and that includes photogrammetry. Once a difficult and costly exercise requiring a plane, new techniques, like drone mapping, have revolutionised the photogrammetry industry for the better. But is it more than just a change of vehicles? And is photogrammetry still a worthwhile option when 3D laser scanning has come so far too?

What Is Photogrammetry & What Is It Used for?

To best appreciate the changes drone photogrammetry has brought, it’s important to understand the fundamentals.

The aim of any photogrammetry is to survey a location to understand the topography, as well as any structures or objects present. This is achieved by taking many overlapping photos, set to a particular scale. Using this scale, it is then possible to estimate the size of any given features in the photograph through standard mathematical equations. In this way, you can accurately calculate the distance between objects in the photographs and so on. These photos and the relevant data gathered from them can then be used to create 3D digital models and even digital twins.

Photogrammetry as a surveying technique has been around since the 19th century. It has helped specialists plot contour lines on topographic maps through to building some of the modern wonders of the world. To do so though, it was an expensive endeavour requiring specialist cameras mounted to a plane. But now, technology has really taken it to the next level with the introduction of drones and cheaper yet still incredibly high-quality cameras.

Additionally, the work that was once done by hand can now be completed far more quickly using specialised software. You can also take data sets and easily export them to other programs to create a fuller picture of the space that you’re working with.

So, thanks to technology, photogrammetry is easier, more affordable, more accurate and faster than ever.

What Are the 2 Types of Photogrammetry?

When you’re talking about photogrammetry, it’s important to know there are two approaches:

  1. Terrestrial, where the overlapping photos are taken close to the ground.
  2. Aerial, where the overlapping photos are taken from above the ground.

Aerial photogrammetry is probably the type most people are familiar with and it’s where drones can really come into play. Rather than the hassle of needing a plane and a pilot like in the old days, photogrammetry surveys can be conducted with a drone mounted with a camera.

How Accurate Is Photogrammetry?

It might be hard to imagine any surveying technique being particularly accurate before the arrival of computers, but old-school surveyors were thorough and accomplished mathematicians. This included knowing how to achieve that perfect and consistent scale in their photographs to precisely measure features and more through photogrammetry.

Nowadays, new technology and specialised software has only made it easier to be incredibly accurate. Of course, user error can still occur, like incorrectly setting up the scale. However, in general, photogrammetry is quite accurate.

What Is the Difference Between 3D Scanning & Photogrammetry?

So how do 3D scanning and photogrammetry compare when it comes to getting the lay of the land? For starters, both are non-contact reality capture surveys that let you learn about and digitise an object or landscape. This can be extremely important for certain projects, like ecological or archaeological ones.

They also both can be done using drones now. Where photogrammetry relies on a drone to take photographs, for a 3D laser scan, the drone uses lasers to create point clouds of data which can then be interpreted by specific software.

Is Photogrammetry Better Than 3D Scanning?

While each technique has their pros and cons, there is a lot to love about photogrammetry, even if its roots are a little old fashioned. For starters, photogrammetry tends to be less expensive. As explained above, you really just need a drone and a high-quality camera, both of which are readily available these days. It can be a bit harder and more expensive to source a 3D laser scanner.

Additionally, if you’re working with a wide range of scales and targeted features, photogrammetry is a more flexible choice. You can really work with anything from the size of a finger to a full mountain range.

You’ll often find, too, that surveyors prefer to use drone photogrammetry over laser mapping when it comes to rendering landscapes. This is because it is better able to capture the realism of the scene — it is taking photos after all. Of course, you do need to be sure you have good lighting and weather conditions for the best results. Regardless, photogrammetry is the go-to for when you’re working with very large detailed areas, like for an archaeological survey or looking at land for development. In contrast, 3D laser scanning is a better option if you want to densely capture a surface with little texture.

Of course, which is best for you depends on what your project requires. One technique may be more effective for meeting your goals. Alternatively, you could even use a combination of the two techniques together to gather as much data as possible.

It’s Time to Fly With Galaxy City

Photogrammetry still serves an important purpose in the geospatial surveying sphere. In fact, it’s one of the key services Galaxy City provides as part of our geospatial capabilities. With experienced technicians and state-of-the-art equipment, we’re able to quickly and accurately gather and record information about your project site, whether it’s an empty field or a bustling building. Get in touch today to learn more about photogrammetry for your next project.