Things to know about photogrammetry

What is photogrammetry?

Photogrammetry is a science that deals with the acquisition, processing, analysis and presentation of spatial information using photographic images. A distinction is made between 2D (orthophotos) and 3D photogrammetry. Both techniques, 2D and 3D photogrammetry, are used as needed in cartography, landscape planning, and for scientific purposes such as documentation and surveying of glaciers or other environmental research.

The history of photogrammetry

The history of photogrammetry dates back to the 19th century, where the first beginnings of photogrammetry can be found in military surveying. Amin Laussedat, a French engineer, developed a method for surveying buildings and landscapes using photography. He used two photographs taken from different positions and analyzed the parallels in the photographs to determine spatial position. In 1859, Laudessat was able to convince representatives of the French military to use this method for mapping and was commissioned to create a map of an area of about 200 hectares. These were the beginnings of photogrammetry.

Source: Wikipedia

2D photogrammetry (orthophotos)

2D photogrammetry refers to the creation of geometrically corrected aerial images, also known as orthophotos, which are used to create topographic maps and terrain models. These images are taken with a camera from the air at a 90 degree downward angle.

Here you can find detailed information about 2D photogrammetry (orthophotos)

3D photogrammetry

3D photogrammetry refers to the creation of 3D models of objects, buildings or landscapes using photos taken from different angles. The photos must be taken at an appropriate scale. In this way, highly accurate terrain models or city models can be created in 3D. Drones are proving to be an extremely useful tool for photogrammetry in this regard. The quality and number of photos are crucial for the result of the 3D model. These photos, sometimes several hundred or even thousands of photos, are generated into a 3D model using photogrammetry software and very high computing power.

How are the images for 3D photogrammetry created?

For best results, images should overlap 60-70% to obtain accurate results. Unlike 2D photogrammetry where overlapping images are taken at 90 degrees down, 3D photogrammetry requires additional images from different angles and heights. Here are some guidelines, but they can be adjusted depending on the object or requirement:

• From a height of approximately 50-60 meters, overlap photos at a 90 degree downward angle.

• Circle the object from a slightly lower height and take overlapping photos at an angle of about 30 degrees.

• Circle the object at about half height and take overlapping photos at an angle of about 45 degrees.

• Circle the object at a low height and take overlapping photos at an angle of about 70 degrees.

Photogrammetry applications

Photogrammetry is used in many areas of industry, research, inspection or surveying. Today, drones can be used to quickly and accurately document very difficult to access areas or dangerous locations and can be used for various applications. The advantage of drones is that they can be used inexpensively, quickly and accurately compared to traditional methods using helicopters or airplanes. It should also be noted that in such a survey from the ground, which takes place in dangerous areas such as steep slopes, glaciers, etc., no human being has to put himself in danger to collect data.

Photogrammetry in archaeology

In archaeology, photogrammetry is used in various fields, here are some examples.

• Aerial archaeology to create high resolution 3D models to prepare excavations and document the results step by step.

• Documentation of excavations or sites to create 3D models and use them for analysis.

• Another type of photogrammetry is close range photogrammetry, which is often used to document archaeological artifacts.

• Documentation of archaeological monuments or archaeological sites

Photogrammetry in geology

In geology, photogrammetry is frequently used to record, document and analyze geological phenomena and structures. Drones are also already increasingly used in geology to collect data from the air and process it photogrammetrically. Some examples of their use in geology include:

• Terrain modeling to create high-resolution digital terrain models for analysis and better interpretation of geological phenomena and structures.

• Surveying and documenting landslides and erosion and measuring and interpreting changes over time.

• Survey and document volcanic structures to detect and analyze lava flows and craters.

• Survey and document faults and fault lines in rock formations for analysis.

• Documenting and analyzing glacial movement and glacial melt.

• Capture surface changes in mining areas, open pit mines, and other geologic events for analysis and documentation of changes from time to time.

Photogrammetry in forestry

In forestry, photogrammetry is used to create survey data or topographic maps to observe and analyze changes in the forest. It can also be used to record the number of trees and the height of trees in a given area. This information can be used to make decisions about forest management, timber utilization, or environmental protection.

Photogrammetry in urban planning

In urban planning, photogrammetry is mainly used to collect and analyze geographic data. Data collected by drones and the corresponding photogrammetry software are used to create digital terrain models, orthographic aerial photographs (orthophotos) and 3D city models. These collected data can then be used to support urban planning projects. The following are just a few examples of the use of photogrammetry in urban planning:

• Analysis and evaluation of land use

• Preparation of land use plans

• Monitoring of construction projects

• Creation of simulation models

Photogrammetry, especially when combined with the use of drones, allows urban planners and engineers to collect and analyze data in a simple and fast way, making urban planning and infrastructure project development much easier and more efficient nowadays.

Photogrammetry in the energy sector

Drones today make it possible to collect meaningful information using various sensors such as thermal imaging cameras or high-resolution cameras with optical zoom. In the energy industry, for example, a large number of thermal images and simultaneous high-resolution RGB images can be used for photogrammetry to then create orthophotographic thermal images and simultaneously an orthophoto for normal visual inspection. Radiometric thermal images can also be used to create maps on which temperature data can be read with pixel accuracy. For large facilities, this can be very helpful in providing a quick overview of the facility. Thus, substations, photovoltaic plants, power plants and much more can be documented and inspected to prevent malfunctions or detect defects.

Photogrammetry with drones can also be used in the energy industry to create topographic maps that can serve as a basis for plant construction. Another application of photogrammetry in the energy industry would be to monitor and document vegetation near power lines, wind turbines, substations, etc.

The future and further development of photogrammetry

Due to the rapid development of artificial intelligence (AI) and the rapid development of drones and sensors such as extremely high-resolution RGB cameras, infrared thermography, LiDAR and radar, photogrammetry will be used in more and more areas. Here are just a few areas where we expect photogrammetry to evolve in the future:

• With the increasing availability of artificial intelligence (AI) and machine learning, photogrammetry will become more automated, allowing for faster and more accurate processing of data.

• Increasingly high-resolution cameras and other sensors such as infrared thermal imaging cameras or LiDAR, as well as improved processing technologies, will increase the accuracy of photogrammetry.

• Through research projects and creative minds, we will continue to explore new application areas of photogrammetry in conjunction with drones and use them efficiently in many fields. Be it in the field of industry, in the energy sector or to protect our planet and climate.

• Due to the increasing availability of drones with high-resolution cameras or satellites, more and more data will be collected and analyzed in the future to cover and plan large areas faster and more cost-effectively.

• The fusion of data collected from various sensors such as LiDAR, radar, infrared thermal cameras, and RGB imagery will enable comprehensive and accurate data collection.

All in all, photogrammetry will become more automated, accurate, and flexible in the future, and will spread to many other fields in climate and environmental research, industry, and energy.

Conclusion on photogrammetry

Photogrammetry is a powerful method of spatial data collection based on the use of photographs. When combined with drone technology, this method can be taken to a whole new level and enable an unimaginable number of applications. Many of these areas have yet to be explored or even discovered, but in other areas such as industry, energy production, urban planning, glacier monitoring, forestry and much more, this method can already be used successfully and extremely efficiently.

The use of photogrammetry allows companies to obtain extremely precise and, above all, up-to-date data from projects, inspections or infrastructures. In combination with infrared thermography (thermal imaging cameras) or LiDAR, comprehensive and precise data collection is made possible. All this can be used to increase the efficiency of maintenance and inspection plans, but also to ensure the safety of people, such as bridge inspections, after environmental disasters, etc. In the future, photogrammetry will be further developed and used thanks to the availability of artificial intelligence, increasingly powerful sensors on drones and creative minds.

Questions and answers about photogrammetry

• How does photogrammetry work?

  Overlapping photos are taken of a specific area or object, which are processed by special software to create a 2D orthophoto or a 3D model. With the help of photogrammetry it is possible to obtain spatial information such as distances, angles or volumes.

• How can photogrammetry be used?

  Photogrammetry can be used to create topographic maps, measure objects, buildings or facilities, monitor and document environmental or climate changes, create 3D models of cities or landscapes, for inspections in the energy sector and much more. Anywhere you want to digitally represent data about a specific object or terrain for industrial purposes, geology, archaeology or environmental and climate research and need precise data.

• What is the difference between photogrammetry and other surveying methods?

  Photogrammetry uses photographs as the data source, while other surveying methods use GPS or total stations to create plans or surveys.

• What equipment is needed for photogrammetry?

  The most common applications of photogrammetry for surveys or inspections require a camera, a drone or aircraft, a very powerful computer and software. However, there are many other types of photogrammetry for imaging small objects or using satellites for larger areas.

• What are the advantages of drone photogrammetry?

  Drones enable the collection of up-to-date data and are very cost-effective to use. With drone photogrammetry, buildings, facilities, infrastructure and landscape can be digitally imaged and provide accurate and up-to-date data for surveying, inspection and many other applications.

• How are the created data processed with photogrammetry?

  The photogrammetry data collected is usually processed using specialized software and powerful computers. The photos are merged and extracted into a 2D or 3D model that contains spatial information.

• What are the application areas of photogrammetry in the energy industry?

  In the energy industry, photogrammetry is used to survey facilities and infrastructures and to create maintenance and inspection plans to detect potential problems at an early stage. For large solar or photovoltaic farms, infrared thermal imaging cameras can be used to create orthophotographic 2D models with precise temperature data and detect defective photovoltaic modules.

• What are the future trends in photogrammetry?

  Thanks to increasingly available artificial intelligence, more powerful cameras and sensors on drones, more and more data is being captured and analyzed faster, more precisely and more comprehensively. Especially in environmental and climate research, this technology can help protect our planet. Many areas of application will only be discovered and explored through creative thinking.