Photogrammetry is a fascinating field that combines science and art to generate 3D data from 2D photographs. This technique, widely used in topography and digital modeling, enables us to determine the shape, dimensions and position of an object in space. Whether using aerial or terrestrial images, the photogrammetry process offers remarkable precision (modeling, georeferencing, measurement, etc.). Discover the many facets and uses of photogrammetry.
How does photogrammetry work?
Definition and fundamental principles
Photogrammetry is the science of determining the geometric properties of objects from measurements taken on images. The fundamental principles of photogrammetry are based on key concepts such as triangulation and parallax.
- Triangulation is a technique for determining the position of a point by measuring the angles between it and other reference points whose position is known. In drone photogrammetry, this concept makes it possible to georeference a pixel in a three-dimensional environment;
- Parallax, on the other hand, is an observation method that exploits the relative displacement of the observer to estimate the distance of an object.
Photogrammetry is also based on the principle of human perception of relief through stereoscopic observation (two points of view, left and right eyes). This is a method of observation which, like our human vision, uses two slightly different points of view to obtain a perception of depth and relief.
Using several images of the same scene (or object) taken from different positions, and with the help of these two essential concepts, we can model 3D shapes from 2D images.
The various stages in the digital photogrammetry process
There are several key stages in the photogrammetric process:
- Photo acquisition: This first phase involves taking photographs of the object or scene to be modeled. The images must be taken from different angles and overlap to obtain a parallax useful for the rest of the process. The choice of shooting equipment and the acquisition method are crucial to ensure the quality and accuracy of the results.
- Image processing and analysis: Following field acquisition, images are orthorectified, processed and analyzed by photogrammetry software to determine the position of the camera during each shot, and to identify common points between overlapping photos.
- Triangulation: This stage uses the information gathered during image analysis to reconstruct the geometry of the 3D scene. Each pixel is associated with a coordinate: longitude, latitude and altitude.
- 3D modeling: Finally, triangulation information is used to generate a 3D model of the object or scene. This modeling can be carried out using photogrammetry software.
Each of these steps requires special attention and specific skills to achieve a high-quality end result. Precise measurement on final images is made possible by the orthorectification process, carried out during image processing, which involves correcting the geometry of an image so that it appears as if each pixel were acquired directly from above. Orthorectification eliminates the geometric distortions associated with the original aerial or satellite imagery.
Why use photogrammetry?
Photogrammetry offers a host of advantages that justify its growing use in a variety of fields.
Firstly, thanks to technological advances such as drones, this technique enables data to be collected quickly and easily. The images required can be captured more quickly using automated, high-performance systems than with traditional methods, and at relatively low cost.
Secondly, the use of a drone for photogrammetry enables access to areas that are difficult to access, be it rugged, inaccessible or dangerous terrain, or even to reach different altitudes depending on requirements and legislation. Drones are therefore an invaluable aid to photogrammetry.
Thirdly, this technique offers remarkable precision. Whether measuring objects or creating 3D models, the results obtained are highly reliable, depending on the equipment used.
Finally, photogrammetry is very affordable, both in terms of cost and technical expertise. Numerous software programs are available to process, generate and analyze images, making this technique accessible to a wide audience.
Some examples of the different types of photogrammetry applications
Civil engineering and engineering
In the field of civil engineering, photogrammetry is particularly useful in helping to design and monitor major construction projects. Thanks to the use of drones, this technique enables topographic surveys to be carried out rapidly and with great precision.
For example, it can be used to model road structures, buildings and construction sites. By generating detailed 3D models and high-resolution images, photogrammetry facilitates project planning and helps improve productivity.
Photogrammetry is also used to produce topographic maps and plans from aerial photographs. These maps can be used as a basis for infrastructure planning.
Archeology
In archaeology, photogrammetry enables precise documentation of excavations and objects discovered, as well as the creation of 3D digital reproductions of archaeological sites and objects.
- Archaeologists use photogrammetry to carry out detailed surveys of archaeological sites, model the topography of the terrain and even of objects found during excavations;
- Thanks to the combination of topography, photography and algorithms, photogrammetry produces a reliable, long-lasting archive, while obeying a scientific protocol closely linked to the act of excavation;
- In addition to its precision, photogrammetry is also appreciated for its speed and affordability. These advantages have led to its rapid and widespread adoption in the field of archaeology.
Technological advances have also led to significant progress in preventive archaeology. Thanks to photogrammetry, it is now possible to create accurate 3D models of archaeological sites before they are destroyed or altered by construction work or natural erosion.
Geology
Photogrammetry enables geological structures or formations to be represented in three dimensions using images.
Photogrammetry is particularly well-suited to the reconstruction of geological outcrops, thanks to inexpensive tools such as a camera, targets and a scaling ruler.
As part of a geological study, photogrammetry can be used to :
- Geological surveying: this is a simple method that can be applied directly by the geotechnician or geologist in charge of monitoring a project, such as the construction of a tunnel;
- Geological mapping: digital photogrammetry is particularly effective for mapping in mountainous regions.
Photogrammetry techniques are useful for detecting terrain anomalies and characterizing soils.
The environment
Drone photogrammetry is highly appreciated for its contribution to environmental characterization. It provides a wealth of information through site modeling and mapping.
Real estate
Photogrammetry has many applications in the real estate sector, including 3D modeling of buildings and precise land evaluation. Industry professionals can benefit from detailed, realistic representations of a property, facilitating valuation and sales.
- 3D building modeling: Photogrammetry can be used to create precise 3D models of existing buildings. These models can be used to represent real estate, enabling potential buyers to visualize the property before they even visit it;
- Terrain assessment: Photogrammetry can also be used to carry out precise terrain assessments, providing detailed information on topography, mapping and features. This information is indispensable for planning construction projects;
- High-quality visualization: Photogrammetry offers high-quality visualization of infrastructures;
- Photogrammetry by drone: More and more real estate professionals are using drones to take aerial shots and obtain high-quality images for photogrammetry. This makes it possible to obtain precise measurements and reliable data on structures and land.
Thanks to these applications, photogrammetry is contributing to the evolution of the real estate sector, offering precise and efficient tools for visualizing and evaluating properties.
Photogrammetry tools and equipment
Which drone to use for photogrammetry?
There are several factors to consider when choosing an effective drone for photogrammetry. Drones recommended for photogrammetry should have cameras of 12 megapixels or more for optimum results. However, cameras with less than 12 megapixels can also be used for photogrammetry, depending on requirements and the technology used. Here are a few examples of suitable drones:
DJI Mavic 3 Pro
The DJI Mavic 3 Pro is the ideal choice for photogrammetry. This compact drone offers an exceptional combination of portability, power and imaging quality.
It is equipped with a Hasselblad CMOS 4/3 camera and a double telecamera, enabling it to produce superior aerial images. What’s more, the drone offers an impressive flight time of 43 minutes, making it easy to carry out complete photogrammetric missions with fewer flights.
The Mavic 3 Pro’s major advantage in photogrammetry, like many other DJI drones, lies in its ability to perform automated flight planning. This makes it possible to carry out complex photogrammetric missions with great precision.
What’s more, the image format produced by the Mavic 3 Pro is compatible with many photogrammetry software packages, making it easy to process and analyze the data collected.
DJI Matrice 350 RTK
The DJI Matrice 350 RTK is a high-end professional drone specially designed for photogrammetry. It offers exceptional positioning accuracy thanks to its integrated RTK system. This drone is equipped with a new TB65 dual-battery system, enabling multiple flights without downtime.
It is distinguished by its ability to accommodate the Zenmuse L2 sensor, ideal for photogrammetric surveys, as well as other sensors depending on specific mission requirements. Its improved video transmission and control system, combined with enhanced safety features, ensures optimum in-flight reliability.
Thanks to its versatility, the DJI Matrice 350 RTK is suitable for a variety of large-scale projects, whether in geology, engineering, real estate or other fields requiring precise, detailed data. With its impressive flight autonomy and great robustness, this drone is a must-have reference for photogrammetry professionals.
WingtraOne GEN II
The WingtraOne GEN II is a new-generation photogrammetry drone, designed to meet the rigorous demands of 3D mapping and modeling. Its maximum flight speed of 16 m/s, coupled with an autonomy of 59 minutes, means that large areas can be covered in a single flight, optimizing uptime.
- 42 MP sensor: Delivers high-resolution images, capturing more detail in every shot;
- High performance: Thanks to its flying-wing architecture, the WingtraOne GEN II boasts a long flight autonomy (up to 59 minutes, depending on weather conditions), covering a greater surface area per flight.
Equipped with intelligent algorithms, the WingtraOne GEN II constantly analyzes all the crucial elements of the flight, before and during it, and notifies the operator of any risk of malfunction. This advanced reliability maximizes drone uptime, increases productivity and guarantees regular report delivery.
Which camera or sensor for photogrammetry?
The choice of camera or sensor for photogrammetry is highly dependent on the type and requirements of the project in terms of quality, accuracy and available resources. You then need to consider the camera’s technical features, such as resolution, lens quality and the possibilities for adjusting shooting parameters.
DJI Zenmuse P1
The DJI Zenmuse P1 is a state-of-the-art photogrammetry camera. Equipped with a 45 MP full-frame sensor, it is capable of capturing images of the utmost precision.
Designed specifically for photogrammetry missions, the Zenmuse P1 pushes the limits of efficiency and precision. It is compatible with the DJI Matrice 300 RTK UAV and DJI Terra photogrammetry software, forming a complete solution for aerial photogrammetry missions.
The P1’s efficiency is such that it can take a photo every 0.7s in flight, optimizing the overlap between images. It’s the tool of choice for all photogrammetry professionals looking for unrivalled performance.
DJI Zenmuse L2
The DJI Zenmuse L2 is another high-performance photogrammetry camera. Designed for use with DJI’s Matrice 300 RTK and 350 RTK flight platforms, this mechanically stabilized gondola incorporates a LiDAR, a high-precision IMU system and an RGB mapping camera with a 4/3 CMOS sensor.
The Zenmuse L2 stands out for its ability to quickly carry out large-area topographic surveys with remarkable accuracy, making it ideal for drone surveying. In operation, it uses DJI Pilot 2 software, which offers various display modes for intuitive visualization of results.
Zenmuse L2 is also capable of emitting up to 240,000 laser points per second. With two scanning modes, it can achieve more uniform and precise capture, meeting the demands of high-precision mapping.
Finally, when used with DJI Terra, the Zenmuse L2 provides a turnkey solution for high-precision 3D data collection and post-processing. Thanks to its powerful hardware, it ensures accurate scanning of complex subjects over a wide range and faster acquisition of point clouds.
Which photogrammetry software?
DJI Terra
DJI Terra is a high-performance photogrammetry software package that transforms the real world into digital data. Perfectly integrated with DJI drones and sensors, it enables analysis of RGB, multispectral and LiDAR data. Its high-performance processing algorithms enable precise, efficient 2D and 3D reconstructions, all within a highly intuitive interface.
Thanks to DJI Terra, users can analyze and visualize their environment with unrivalled efficiency. This comprehensive platform is capable of rapidly processing photogrammetric datasets, making the mapping process more user-friendly. Tools are also available for calculating distances, areas and volumes.
The Pix4D solution
Pix4D offers a range of software solutions to meet a variety of photogrammetry needs. Pix4D products transform aerial and terrestrial images into precise, georeferenced 3D maps and models. The PIX4D suite includes several reference software packages for topography, geomatics and architecture professionals, enabling them to generate plans, 3D models, orthomosaics and point clouds from drone photos.
PIX4Dsurvey is another key product, extracting and vectorizing the essential elements of photogrammetry. To plan and carry out your flight missions online, the free PIX4Dcapture app is available on Android and iOS. For online image processing, Pix4Dcloud offers a simple platform for processing, visualizing, inspecting, sharing and generating models with photogrammetry algorithms.
Using these tools, you can :
- Merging aerial and terrestrial data while guaranteeing accuracy;
- Produce quality deliverables by generating accurate 3D digital models and maps;
- Digitize the world around you by capturing images and processing them on your computer or in the cloud.
What training or courses are available for photogrammetry?
It’s important to choose a course that matches your skill level, career goals and budget. Training courses may also be eligible for funding from various organizations.
Photogrammetry training can be delivered in several ways: online, face-to-face or blended. Organizations such as DroneXperts offer various training courses, such as :
Advanced drone pilot training
Theadvanced operations training is essential for those wishing to specialize in drone photogrammetry. This course is designed to give you the skills you need to pilot a drone weighing over 250 grams in controlled airspace, while complying with current regulations.
It includes various aspects such as :
- In-depth knowledge of piloting rules in urban and complex environments;
- Advanced exam preparation on the Transport Canada website to obtain the Pilot Certificate – Advanced Operations;
- Know the different aeronautical restricted zones.
These courses are designed for gradual learning, with course support included.
DJI L1 Lidar Training
The DJI L1 LiDAR training training is essential for mastering the use of LiDAR (Light Detection and Ranging), a laser-based remote sensing technology used for monitoring and mapping natural resources and infrastructure. This training course will enable you to perfect your skills in drone remote sensing and master LiDAR data acquisition missions.
During the course, you will learn to :
- Process LiDAR raw data;
- Understand the difference and complementarity of LiDAR VS photogrammetry;
- Prepare a typical remote sensing mission.
We recommend that you have taken the mandatory remote control training course, and have a solid grounding in photogrammetry.
Pix4D mapper training
Visit Pix4D mapper training is a complete program designed to introduce you to the functionalities of Pix4Dmapper software. This training course will enable you to master the different stages of using the software and its functionalities, from data collection to modeling.
During the course, you will learn to :
- Understand the main photogrammetry steps in Pix4Dmapper;
- Process your projects using the software;
- Take full advantage of all Pix4Dmapper features;
- Apply concrete examples, such as modeling, classification and orthomosaics.
Professional opportunities and jobs in photogrammetry
Photogrammetry offers a wide range of career opportunities in different sectors. In fact, a number of professions are linked to the use of this technology.
These include photogrammetry technicians, who produce plans, graphs, tables and topographic maps from aerial photographs. Some geomatics or surveying technicians may also use photogrammetry in their work.
Other professions, such as photogrammetry technologist, require more specific skills. Finally, teaching positions in photogrammetry are also available for those wishing to pass on their knowledge in this field.
Beyond these specific professions, photogrammetry can be used in many other sectors, such as construction, mining or topography.
In conclusion
What are the advantages of drone photogrammetry and how accurate is it ?
In conclusion, photogrammetry offers several significant advantages. First and foremost, it offers maximum precision when measuring objects or scenes. This level of precision is particularly useful in fields such as archaeology or civil engineering, where detailed measurements can have far-reaching implications.
What’s more, the accessibility and speed of data collection are two other major advantages of drone photogrammetry. Thanks to advances in technology, aerial photography is now possible to cover vast areas of interest, including those that would be difficult to access by other means.
What’s more, photogrammetry can be used to create photographic archives, making it easier to track the evolution of a structure or plot of land over time. For example, this can be useful for monitoring the erosion of a river or the evolution of a crime scene.
Finally, photogrammetry is a cost-effective technique. The investment required for the necessary equipment, such as a camera or drone, is relatively low. What’s more, numerous photogrammetry software packages are available, making this technique accessible to a wide audience, without the need for advanced technical skills.
What are the limits and future challenges for photogrammetry?
Photogrammetry, like any technology, presents certain challenges and limitations. Constraints include environmental conditions, which can affect the quality of captured images. Poor lighting conditions or inclement weather can hamper the accuracy of photogrammetric measurements.
Managing the data collected can also be a challenge. Photogrammetric data can be voluminous, and processing them requires significant computing resources.
Despite these challenges, photogrammetry continues to develop and evolve to overcome these obstacles. One of the main areas for improvement concernsprocess automation, both for image capture and processing. What’s more, theintegration of artificial intelligence into image processing is another major challenge for the future of photogrammetry.