What is Drone Photogrammetry?
Drone photogrammetry is the science of taking measurements from photographs. It’s commonly used in surveying and mapping applications, as well as in 3D modeling. Photogrammetry uses a variety of techniques to measure things like distance, angles, and elevation.
Drone photogrammetry is not to be confused with drone photography, which is simply taking pictures with a drone. While photographs are essential to photogrammetry, the process involves much more than just taking pictures.
The basic idea behind drone photogrammetry is to take multiple pictures of the same object or area from different angles. These images can then be fed into specialized software, which uses algorithms to reconstruct the three-dimensional scene.
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How Does Photogrammetry Work?
Photogrammetry works by using a series of photographs to map out an area. The photos are taken from different angles and perspectives, with the assumption that they will overlap. This overlap is essential, as it allows for measurements to be taken from the photos.
This works because the perspective in each photo is slightly different, such that a computer can track different points from one photo to the next. This process is known as “image matching,” and it’s how photogrammetry software is able to reconstruct a 3D model from a series of 2D photos.
There are a variety of photogrammetry software programs available, each with its own strengths and weaknesses. Drone photogrammetry software solutions, in particular, include Pix4D, OpenDroneMap, DJI TERRA, and others.
Photogrammetry is a technique used in surveying to measure the three dimensional coordinates with the help of photography. The term “photogrammetry” is composed of the words “photo” and “meter” meaning measurements from photographs. The output of photogrammetry is typically a map, a drawing or a 3D model of some real-world object or land mass."
- Bill Winston | Using Drones for Photogrammetric Surveys | Washington University in St. Louis
Common Photogrammetry Terminology
The jargon associated with photogrammetry can be confusing to those who are new to the field. Here are some common terms you’ll come across when doing research on photogrammetry:
- UAV: Unmanned Aerial Vehicle. This is another name for a drone. It’s used to refer both to consumer drones and to larger, more sophisticated drones that are used for commercial purposes, or even military purposes.
- Orthomoasic Map: A map that has been created using photogrammetry, where the scale between ground objects and their represented size on the map is uniform. This type of map is useful for applications where accuracy is important, such as surveying.
2D Orthomosaic Map of Construction Site
- Orthophoto: An orthographic projection of an image, where the scale is uniform throughout the image. This type of image can be thought of as a “flattened” version of a photo, and it’s often used in photogrammetry because it makes measurements easier to take.
- Remote Sensing: The process of gathering information about an area without being in physical contact with it. This can be done using drones, satellites, or even ground-based sensors.
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- Geographic Information System (GIS): A system that is used to collect, store, manipulate, and display geographical data. GIS systems are often used in conjunction with photogrammetry to create maps and 3D models.
- Metadata: Data that describes other data. In photogrammetry, metadata can include information such as the date and time a photo was taken, the GPS coordinates of where the photo was taken, the make and model of the camera used, and more.
- LiDAR: Light Detection And Ranging. This is a type of remote sensing that uses pulses of laser light to measure distance. LiDAR can be used to create 3D models, and it’s often used in conjunction with photogrammetry.
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A Proven Roadmap of Success for Implementing Drones in Construction.
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How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
Use Cases for Aerial Photogrammetry
Drone photogrammetry has a wide range of potential applications. Here are some examples of how it can be used.
Energy Industry
The energy industry has many high-risk, high-reward projects. For example, oil and gas exploration can be extremely lucrative, but it also comes with a certain amount of risk. If a well is not properly drilled, it can result in an environmental disaster.
This is where drone photogrammetry can be useful. Drones can be used to survey an area before drilling begins, allowing energy companies to map out the terrain and identify potential hazards. This information can then be used to plan the drilling process and minimize the risks involved.
The renewable energy sector, too, can benefit from drone photogrammetry. For instance, photogrammetry can determine rooftop suitability for minimum size PV (photovoltaic) installations. It can also help accurately capture large territories for potential solar farms.
In one recent case study, drone photogrammetry was used to model a flare tower at a gas plant. Alternative methods would have required retrieving data from a far distance, and using a “rope access team” to shut the flare down. Instead, the drone flew close to the flare, capturing a series of high-definition photographs that were later used in the model.
Construction Industry
The construction industry is another sector where drone photogrammetry can be useful. Construction sites are often large and complex, making it difficult to get a clear overview of the project. This can lead to errors and delays.
Drones can be used to create a detailed map of a construction site, allowing for better planning and coordination. This is especially valuable for larger projects, such as the construction of a new highway or industrial warehouse.
In addition, drones can be used to inspect finished products, such as bridges or buildings. This can help identify potential problems early on, before they become expensive repairs.
Engineering Industry
Engineering firms often need to collect data about existing structures, such as bridges or dams. This data can be used to assess the condition of the structure and identify potential problems.
In the past, this type of data collection was often done using ground-based sensors, which could be time-consuming and expensive. Drones, on the other hand, can quickly and easily collect the data needed for engineering applications.
To give one example, the US Army Corps of Engineers used a WingtraOne drone to perform a drainage study on the Chennault International Airport, which was experiencing drainage issues. With over 3 kilometers of runway, traditional surveying techniques would have involved a lot of manpower.
Benefits of Drones for Photogrammetry
There are many reasons why drones have become such popular tools for photogrammetry. Here are some of the most significant benefits.
Fast & Comprehensive Data Collection
Drones can cover large areas quickly and efficiently. This is especially valuable for large construction projects or engineering surveys, where time is often of the essence. In addition, drones can access areas that would be difficult or impossible for ground-based surveys, such as roofs or cliff faces.
Prior to the advent of drones, aerial surveys were often conducted using manned aircraft, which could be expensive and logistically complicated. Drones have made aerial surveys much more accessible, both in terms of cost and complexity.
Consider, for example, a construction site that covers 500 acres. A drone survey of this site would take a matter of hours, whereas a ground survey would likely take days or even weeks. In addition, a drone survey would be far more comprehensive, as it would cover the entire site, whereas a ground survey would likely miss areas that are difficult to access.
Incredibly Accurate Measurements
GNSS-enabled drones can collect data with incredible accuracy. This is especially valuable for applications where precision is important, such as surveying or engineering.
In the past, aerial surveys were often conducted using manned aircraft, which could only achieve accuracies ranging from meters to decimeters. Drones, on the other hand, can achieve accuracies of millimeters to centimeters.
Accuracy is often described in terms of the ground sample distance (GSD), which is the real-world size of a pixel in the images. A 1cm GSD is considered very accurate, which is achievable with a high megapixel camera. Of course, it also depends on the altitude at which images are captured.
Cost-Effective & Versatile
Entry-level camera drones can be had for under $500, making them much more affordable than traditional aerial survey methods, such as manned aircraft or satellites. Hiring a drone service provider is also an option for those who don’t need a drone on a full-time basis.
In comparison, hiring a manned aircraft pilot can cost thousands of dollars per day, and satellites can cost tens of millions of dollars. This makes drones the clear choice for most photogrammetry applications.
Drones are also very versatile. They can be equipped with a variety of sensors, such as cameras, LiDAR, thermal cameras, and more. This allows them to collect data for a wide range of applications, such as mapping, surveying, and 3D modeling.
Comparing Capture Methods: Photogrammetry vs LiDAR
There are two main methods for collecting data for photogrammetry: photogrammetry and LiDAR. Both have their own strengths and weaknesses, and the right choice depends on the specific application.
Photogrammetry has a number of advantages, such as its low cost and versatility. However, it also has some drawbacks, such as its reliance on good lighting conditions and its inability to penetrate clouds or vegetation. It’s also subject to effects like bloom, or the washing out of bright areas in photos; and lens distortion, which can cause objects to appear larger or smaller than they actually are.
LiDAR, on the other hand, is much more expensive, but it doesn’t rely on good lighting conditions and it can penetrate clouds and vegetation. It’s also not subject to bloom or lens distortion. However, LiDAR has its own set of drawbacks, such as its reliance on line-of-sight and its shorter range.
The choice of capture method depends on the specific application. For example, if accuracy is paramount, then LiDAR is likely the better choice. However, if cost is a concern, then photogrammetry may be the better option.
Best Drones for Photogrammetry
Not all drones are created equal. Some are better suited for photogrammetry than others. Here are some of the best drones for photogrammetry, based on a variety of factors, such as price, performance, and features.
DJI Matrice 300 RTK + P1 Sensor
Pros: 55-minute battery life, RTK positioning, robust, transportable, stable performance, wide range of available payloads,
Cons: expensive, small controller screen,
Estimated Cost: $20,000 USD
The DJI Matrice 300 RTK is a high-end drone that is specifically designed for commercial applications. It’s one of the most expensive drones on the market, but it’s also one of the most capable.
The Matrice 300 RTK has 6 directional positioning, is capable of up to 55 minutes of flight time, has a 15 km max transmission, and it can operate in extreme cold and heat. It’s designed for stable, high-performance video even in windy and harsh conditions.
The Matrice 300 RTK also has a number of advanced features that make it well suited for photogrammetry, such as its ability to fly in GPS-denied environments and its foldable design that makes it easy to transport.
The Zenmuse P1 sensor is an add-on photogrammetry camera payload for the Matrice 300 RTK. This full-frame 45MP sensor costs nearly $7,000, but it’s highly performant, with 3cm horizontal accuracy and 5cm vertical accuracy, a lightning-fast shutter speed, and it can cover 3 square kilometers in one flight. Altogether, a system will cost about 20K USD.
WingtraOne Gen II
Pros: Advanced reliability, interchangeable cameras, remote ID ready, precision landing accuracy
Cons: less redundancy, only compatible with the included tablet, not beginner friendly, cannot reprogram flight mid-mission, limited to five payloads
Estimated Cost: $32,000 USD
The WingtraOne Gen II is a drone that is specifically designed for surveying and mapping applications. It offers advanced reliability through predictive maintenance features, smart notifications, and more.
The camera is an Oblique Sony a6100, with 24MP resolution, and GSD (ground sample distance) down to 1.6cm/px. With a wide angle field of view, this drone is particularly useful for capturing the fronts and sides of buildings. The system isn’t cheap, at around $32,000.
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DJI Phantom 4 RTK
Pros: Affordable, precise imaging, beginner-friendly, mechanical shutter, RTK is included, reliable design
Cons: Fairly low battery life, fixed payload, older aircraft, small remote controller screen
Estimated Cost: $6,500 USD
Released in late 2018, the DJI Phantom 4 RTK was designed for extremely accurate aerial mapping using real-time kinematic positioning. New units are no longer being produced, but it came out with a price tag of $6,500.
There’s not yet a DJI Phantom 5, but the Phantom 4 RTK remains one of the best drones for photogrammetry on the market. It’s equipped with a 20-megapixel camera and a 1-inch sensor. It also has a flight time of up to 30 minutes and a maximum range of 7 kilometers.
Intelligent software helps to create precise imaging, such as the “TimeSync” system that continually aligns the flight controller, camera, and RTK module. It’s also very beginner-friendly, as it connects to most Android or iOS devices.
SenseFly eBee X
Pros: Extremely lightweight, long battery life, highly accurate, remote ID ready, variety of interchangeable payloads
Cons: More difficult to operate, large open space required for takeoff and landing, ground station sold separately
Estimated Cost: $20,000 USD
The SenseFly eBee X is a fixed-wing drone that can fly for up to 90 minutes with 0.6 inch accuracy. It’s also very lightweight, at just 3.6 pounds, which allows it to operate within more regulatory frameworks than some of the heavier drones on this list.
The system’s payload is also interchangeable, making it versatile for different needs, such as creating orthomosaic maps, mapping routes, or creating thermal maps.
The fixed-wing design is meant to enable larger-scale mapping capabilities, and cover most sites in just one flight. Complete packages come in at “generally less than $20,000,” making it one of the more expensive options.
Censys Sentaero BVLOS
Pros: Can operate in harsh conditions, detect-and-avoid system, BVLOS-oriented, high level of redundancy, VOTL (Vertical Take Off and Landing) equipped, 11 different payload options
Cons: Expensive, hard to transport, longer setup time
Estimated Cost: $50,000 USD
Leasing Option: Equipment packages as low as $1,000 USD/month.
Full BVLOS Package for $5,000 USD/month
The Censys Sentaero is a high-end drone that is specifically designed for long-range, beyond visual line-of-sight (BVLOS) applications. It can fly for up to 1.5 hours, or 55 miles, in conditions of 30 mile per hour wind.
It has a “universal payload,” which means it’s easy to swap out different cameras, sensors, or other payloads to meet different needs. For instance, while one user may prefer faster data collection with a lighter load, another may opt for more comprehensive coverage that’s worth the weight penalty.
There is an extensive range of photogrammetry payloads that are compatible with the Sentaero BVLOS:
- Sony A6400 (24MP)
- Sony ayR3 (42MP)
- PhaseOne ixm100 (100MP)
- MicaSense RedEdge MX
- MicaSense Altum PT
- Workswell Radiometric
It also comes with a detect-and-avoid system that uses an electro-optical sensor to detect potential in-flight risks. If you’re looking for a drone that is specifically designed for long-range BVLOS applications, then the Censys Sentaero is a great option.
How to get started with UAV Photogrammetry
If you’re interested in getting started with drone photogrammetry, then there are a few things you need to know. First, you need to choose the right drone for your specific application. Second, you need to choose the right software solution. And third, you need to make sure you have the proper permissions and licenses in place.
Choosing the right drone is essential. Not all drones are created equal, and some are better suited for photogrammetry than others. Be sure to do your research and choose a drone that is specifically designed for your application.
Choosing the right software solution is also essential. There are a variety of photogrammetry software programs available, each with its own strengths and weaknesses. Be sure to choose a program that is specifically designed for drones and that has the features you need.
Finally, make sure you have the proper permissions and licenses in place before you start flying. Depending on where you live, you may need a special permit or license to fly a drone commercially. Be sure to check with your local authorities to find out what is required.
For more information on how to get started with drone photogrammetry, consult The Drone Life. Simply tell us your needs, receive a free same-day quote, and get professional drone services.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
