Given today’s technological advancements, photogrammetry seems new, but actually, it’s really old. The method of reconstructing measurements is rooted in principles of perspective and projective geometry practiced by artists like Leonardo da Vinci and formalized into a science by German mathematicians in the late 19th century. Yet the photogrammetry field is rapidly evolving through innovations in software and aerial photography.
What Is Photogrammetry?
Photogrammetry involves taking photos of an object or environment from different angles and using these images to generate reliable measurements. Professionals often depend on high-quality cameras to take photos, attaching them to an aerial craft, like a drone, or to a ground-based support system, like a tripod, or simply using a handheld camera.
What Is Photogrammetry?
After taking photos from different locations, teams can gather enough visual data to inform drawings, topographical maps, meshes and lifelike 3D models. Advanced software tools have made the last option more prominent since professionals can leverage these technologies to create digital assets with pixel data gathered from photographs. The technique has become essential for various tasks, including surveying construction sites and flood zones, assessing crop health and exploring fossil sites.
In January of 2021, at a clay mine near Golden, Colorado, Alena Iskanderova made a startling discovery: The tracks of an ancient relative of the crocodile — once preserved for some 100 million years — had been largely erased by erosion.
In the 11 years since paleontologist Martin Lockley, an associate curator at the University of Colorado Museum of Natural History and professor emeritus at the university, first documented the tracksite, the fossilized footprints left by the animal had lost much of their depth — from roughly 7 to 12 millimeters down to 3 to 4 millimeters, Iskanderova said.
That the effects of the elements could visibly diminish the tracks in such a short time points not only to their fragility in the face of climate change and other anthropogenic threats, Iskanderova said, but the importance of photogrammetry as a means of preserving the geologic record.
“Sometimes tracks are the only presence of animals in any paleoenvironment. So [photogrammetry] is very important for us to know what kind of animals were there,” she said. “The tracks also show us their behavior. Sometimes we can tell, for example, that there was a group of dinosaurs migrating from one point to another.”
Iskanderova is a close-range photogrammetrist with a specialization in paleontology. She uses a Canon 5D Mark II camera with a 24-mm lens to do much of her work, which has included documentation of dinosaur tracks. Most of her work occurs in the South Platte formation — a sandstone-rich rock bed in the foothills of Colorado’s Front Range.
“Sometimes tracks are the only presence of animals in any paleoenvironment. So [photogrammetry] is very important for us to know what kind of animals were there.”
After snapping hundreds of overlapping pictures, Iskanderova uses software to patch them together into a single 3D image. By aligning pixels in the photos, the software renders something called a point cloud — a three-dimensional constellation of colored dots that reveal the contours of a surface. These points are then layered with a textured mesh to create lifelike visualizations, including depth maps showing the geolocated contours of a surface.
“This is why photogrammetry should be taken as a best practice for fossils and tracks studies,” Iskanderova wrote. “[Many scholarly] papers give measurements as numbers but don’t document how the measurements are made in connection to the start and end points. Each scientist, or a fieldwork assistant, will take the measurements differently. With photogrammetry, you can record not only the length, width and depth [of tracks] but also the start and end points.”
How Does Photogrammetry Work?
The evolution of photogrammetry has accelerated as expectations for image quality have risen. Professionals now assume they’ll be able to take multiple aerial shots of a site and collect accurate visual data, so the industry has come to lean heavily on software and drone technology. As a result, teams have upgraded from taking photos with handheld cameras to commanding drones that can compile data from numerous angles.
Analyses from Data Bridge Market Research predict the photogrammetry software market will see a compound annual growth rate of more than 13 percent between 2021 to 2028, with photogrammetry software expected to reach a market value of $2.56 billion by 2028.
“I think the big revolution has been with drones,” Tristan Randall, a strategic project executive at the architectural software company Autodesk, said. “In the context of a construction project, for example, where you want to monitor your site conditions, you can purchase drones that cost a couple thousand dollars. So capturing the photogrammetric data has become much, much easier.”
Photogrammetry does not require highly sophisticated cameras, Randall said. It can be performed using digital single-lens reflex (DSLR) cameras, video reels, satellite photos or even images captured with an iPhone — virtually any digital camera that can store multiple images.
“I think the big revolution has been with drones ... capturing the photogrammetric data has become much, much easier.”
But the low-cost availability of drones has opened a once largely terrestrial application to a range of new airborne possibilities — from creating large-scale maps to assessing crop health or planning for emergency relief operations to producing lifelike 3D models of buildings, roadways and flood zones.
A photogrammetrist can buy a serviceable drone for as little as $800, said Christopher Kabat, the owner and founder of the drone consultancy ProAerial Media. Once programmed, the drone can capture hundreds of photos of a large-scale real-world environment, like a subdivision or city district, in hours.
Prior to the flight, the pilot selects the flight path and the number of photos the camera will take, based on their desired output resolution. Outfitted, typically, with a one- to two-inch diameter camera on a rotating gimbal, the drone passes back and forth over the landscape taking pictures — hundreds of them — for later processing.
“It’s literally taking every image and taking all the pixels in each image and looking for another image with at least three matching pixels,” Kabat said. “And it’s going to do that for every single photo that you have.”
Depending on the goals of a project, teams can use drone-based photogrammetry to create photorealistic orthomosaic maps corrected for the curvature of the Earth, capture valuable volumetric data — like the amount of soil a building team needs to extract to dig a foundation — or generate interior models for virtual home tours on real estate sites like Zillow. Aerial photogrammetry, though, tends to work best for large-scale projects, not fine architectural details, which are often represented with laser scanning.
The Google Earth project to map cities in 3D actually used both technologies, Randall said, capturing large regions with photogrammetry and applying signature building features with manually scanned data.
“The key thing to remember is that [a point cloud] is a very, very accurate representation of the physical features of a site,” Randall said. “We call it ‘mowing the lawn,’ because you’re basically moving the camera in lines that overlap. And then you use those photos in, say, an engine like Autodesk ReCap, to stitch them together.”
Photogrammetry vs. Laser Scanning
Laser scanners can produce high-resolution 3D models and maps, often at a higher resolution than what can be achieved using photogrammetry. Yet they tend to be expensive — sometimes tens of thousands of dollars, according to Randall — and they must be moved into position by human operators to “see” their targets.
“You can imagine a construction site 20 miles from the city,” Randall said. “A pilot has to fly all the way from the airport and then go back. Even inside a building, you have to move the scanning instrument all over the site to capture different viewpoints.”
But drone photogrammetry has its limitations too. Most U.S. airports, Kabat said, are surrounded by LAANC (low altitude authorization and notification capability) grids that require formal FAA airspace authorization. A flight can be ground sampled at a given height — say, 137 feet — but fall within a restricted zone that limits the flight ceiling to 100 feet. If not coordinated in advance, that can throw a wrench in a mapping project.
“If you were flying in North Carolina, Illinois, Wisconsin — anywhere there’s much denser vegetation, photogrammetry will never be able to interpret the ground data because it can’t penetrate past the canopy roof of the trees.”
Drones — more specifically, their cameras — also have trouble seeing through foliage. Kabat’s company operates in the desert landscape of southern Nevada and areas of Arizona and Utah, where photogrammetry works well.
“But if you were flying in North Carolina, Illinois, Wisconsin — anywhere there’s much denser vegetation, photogrammetry will never be able to interpret the ground data because it can’t penetrate past the canopy roof of the trees,” he said.
Building edges can also be problematic. Unlike laser scanners, which measure distances as a function of the time it takes light beams to reflect off a target and return to their source, photogrammetry uses pixel matching to approximate distance.
“So depending on what’s in those pixels, you may run into challenges. If you’re shooting from directly above a building, you’re not going to be able to represent that vertical edge with as much accuracy,” Kabat said.
Uses of Photogrammetry
Today, photogrammetry is used in commercial applications as diverse as public safety, construction, civil engineering, automotive manufacturing, agriculture and military reconnaissance. And a growing number of use cases has been a boon for the software companies that provide 3D modeling and post-production tools.
- Real Estate
- Renewable Energy
- Cultural/Environmental Preservation
Advancements in the field have turned photogrammetry into an efficient, cost-effective method for collecting accurate data. In addition, drone technology has allowed teams to capture images in areas that were previously inaccessible. Industries have come to realize the benefits of photogrammetry, adopting it as their main method for gathering visual information.
The ability to create multiple detailed images of an object has made photogrammetry a staple in archaeology and real estate. Archaeologists apply the technique to extract details that photography can’t capture, such as the features of individual stones within a structure. Meanwhile, real estate companies have adopted photogrammetry’s 3D modeling capabilities to conduct virtual tours of spaces.
Even the renewable energy sector has found a way to make photogrammetry work to its advantage. Organizations develop holistic models of landscapes by taking images with drones. Teams can then gauge what kind of impact wind turbines and other structures would have on nearby communities and the surrounding environment.
From piecing together a detailed 3D model of a building to locating artifacts within a topographical map, many actions become possible with photogrammetry. Below are a couple in-depth examples of how industries have embraced this developing field, harnessing visual data to create more refined maps, models and more.
Photogrammetry in Construction
Over the past decade, aerial photogrammetry has radically transformed the construction industry. Instead of hiring a survey team to spend weeks photographing a site with GPS-synced tripods, developers can send a drone into the air to capture site conditions in hours, often at a much lower cost, said Ryan Sweeney, a sales manager at the Denver office of the photogrammetry company PIX4D.
Drones are good at capturing high-resolution photographs, in part because they fly so low compared to human-piloted planes. Drones can also capture a site from multiple vantages and reach places that might otherwise be dangerous for humans to be — like hazardous chemical sites.
At a typical construction site, about 500 images captured by a drone in a 30-minute flight can be processed on a personal desktop computer in roughly two hours, Sweeney said. Flight height, camera quality and the level of photo overlap all affect the quality of the point cloud and final outputs. A 75 percent horizontal and vertical overlap is a good target for a quality data set.
In addition to knitting the photos together, software modeling tools or photogrammetry platforms align geotagged pixels against cartesian coordinates ground sampled locally or imported from networked GPS data. The reconstructed image files are, thus, correlated one-to-one with their real-world locations — what some refer to as digital twins. These outputs can be represented as 3D building models, topographical maps, depth maps, contour line drawings and 2D orthomosaics.
Because these renderings are accurate to within inches, architects and engineers can use them to update working “as-built” models so they reflect on-the-ground conditions.
Meanwhile, construction managers can use the 3D models to keep tabs on large-scale development projects, while working remotely.
Photogrammetry in Documentation and Preservation Efforts
Drone technology is quickly getting more advanced and adaptable. Newly developed aircrafts are expected to have swappable payloads, meaning they will let users exchange a standard camera for a zooming camera, thermal imaging camera or LiDAR (light detection and ranging) camera.
The promise of modular camera options is exciting to practitioners like Kabat, but the market for newer technologies will likely take some time to ramp up.
“Most people still don’t even know what photogrammetry is,” Kabat said. “That’s the biggest challenge: just making people aware that you can use photogrammetry to solve problems.”
“It’s not something new,” Iskanderova added. “But in certain fields, like, for example, paleontology, it’s a relatively new and growing field. And, right now, I see many, many students studying photogrammetry and doing projects. Many old-school professors are also interested in photogrammetry.”
“Most people still don’t even know what photogrammetry is. That’s the biggest challenge: just making people aware that you can use photogrammetry to solve problems.”
And it remains an active field for hobbyists. During his off-hours, Kabat traces the history of remote stretches of the American southwest with drones and handheld cameras, capturing artifacts in ghost towns and abandoned mines near Las Vegas, and Native American petroglyphs he finds along the Old Spanish National Historic Trail running from Santa Fe, New Mexico, to Los Angeles.
Though the scale of the project is different, it’s not so far removed from what Iskanderova is doing at a more granular level with dinosaur tracks — reconstructing the fragile outlines of an environment with photogrammetry to document its existence and, hopefully, preserve it for posterity.
“With tracks or any fossils, it’s pretty much detective work,” she said. “You just go in and slowly find more details, making a story behind the remains.”
As the photogrammetry field has increased in popularity, so too have efforts to democratize the technique. No longer does photogrammetry software belong solely in the hands of professionals who have the appropriate training. Now, everyday individuals can acquire the technology. From free programs to pricier options, here are a few examples of popular software that professionals and casual users have come to prefer.
Meshroom is a free program that is offered through AliceVision and operates on Windows and Linux systems. The software is designed to be intuitive to users of all levels, relying on various images of an object to calculate measurements and create a mesh. Users can then alter specific nodes, adjusting and retexturing 3D models to their liking.
The result is a customized experience that allows users to make the software their own. For those who want to work on more challenging projects, Meshroom can also process panorama images. This software may be free, but it still remains helpful as beginners expand their skill sets and start to branch out into different areas of photogrammetry.
ELCOVISION 10 debuted in 1986, earning its title as the first photogrammetry system for PCs. The program has taken major strides since its inception. In 2005, ELCOVISION 10 featured the ability to automatically orient freehand images. The software has most recently showcased automatic high-density point clouds. This latest feature means ELCOVISION 10 can produce images with stunning accuracy, rivaling that of laser technology.
The software only runs on Windows and works for both aerial and on-ground photogrammetry projects. Those looking to get the most out of this program should research which version of ELCOVISION is ideal for their needs. Demo versions of the software are available upon request, and the ELCOVISION team can always address questions about product features and costs.
A more advanced option on the market for professionals is the PIX4Dmapper tool. This software inputs data from multiple images taken with a camera or drone, converting this data into detailed 3D models and digital maps. Users can also leverage the rayCloud tool to make adjustments to their models, refining their reconstructions to represent the original images as close as possible.
PIX4Dmapper is created with professionals in mind, so it is on the more expensive side. However, it does provide plenty of flexibility, working well with macOS, iOS, Android and Windows formats. Drone enthusiasts will appreciate PIX4Dcapture, which is a free mobile app that allows users to control drones and take various pictures for photogrammetry purposes.