Photogrammetry: How good is this scanning method?
Photogrammetry is a highly exciting, but by no means entirely new process. Already in the middle of the 19th century, this process was theoretically advanced in France and Prussia. Even today, however, image measurement is still one of the most famous measurement methods and evaluation procedures. How exactly this works and what software is available for support, you will learn below.
The most important in a nutshell
- Photogrammetry is a process that uses photos to create 3D models
- The method is frequently used, for example, by construction companies, architects or also for land surveying.
- Photogrammetry is divided into two types: close-range photogrammetry and aerial photogrammetry.
- With the help of various software programs, the work in dealing with photogrammetry can be significantly facilitated
What is photogrammetry?
Photogrammetry is also called image measurement. This is a group of non-contact measurement methods that can be used to determine the position and shape of an object from its photograph. This sounds terribly complicated, but it can be done more simply. In other words, photogrammetry is used to create a 3D model from photographs. Even if there is no direct scanning as in other methods, photogrammetry is a method for 3D scanning.
For this process, various coded and uncoded reference points are attached to the respective object prior to measurement. In addition, the positioning of scales in the measurement environment takes place. The object is now photographed from different angles with a camera. The photogrammetry software then generates a precise model using mathematical calculations.
Photogrammetry is distinguished between two different types. Depending on the distance and the location of the photograph, we speak of either aerial or satellite photogrammetry or close-range photogrammetry.
Close-range photogrammetry is mainly used to create comparatively small 3D objects or smaller buildings. In this case, the images are taken with a camera on a tripod from a relatively short distance.
In a sense, the exact opposite of this is aerial photogrammetry. In this case, the photos are created from a great distance and shot, for example, from an airplane or a drone. This approach is particularly common when creating topographic maps. One advantage of this is that the drones can effortlessly target areas that humans cannot reach in a safe manner.
Meanwhile, there are numerous photogrammetry programs that you can rely on as a user. Since it is not easy to get an overview of the offers, some of which are free and some of which require a fee, you will find a small overview here.
Autodesk ReCap is one of the most popular photogrammetry programs. This has already been used, for example, by the US Bureau of Reclamation, which uses it to monitor Glen Canyon Dam. The abbreviation ReCap stands for Reality Capture. Thus, this software generates real images produced by aerial photogrammetry or close range photogrammetry. In the Pro version you also have access to the other software programs such as ReCap Photo or ReCap Mobile.
AliceVision Meshroom is interesting as photogrammetry software mainly because you can use it completely free of charge. The open source software is used to create network structures of the photos. These in turn are then used to build 3D models. AliceVision Meshroom is constantly driven forward in development by a large community.
In a way, Pix4D is a real all-rounder in the field of photogrammetry software. The special feature: This software helps you not only to create the models, but also to take the pictures. For this purpose, various mobile apps are available to turn simple drones into true mapping tools. The scope of Pix4D can be divided into several areas. With Pix4Dmapper you will find a special software for mapping using drones. With Pix4Dcapture a software for optimized images and with Pix4Dbim a software for earthworks or infrastructure management.
Agisoft Metashape belongs to the rather high-quality programs for photogrammetry. The license fees are correspondingly high. The so-called Professional Edition demands a cost of more than $3,000. However, with the Standard Edition, the program is much more affordable at less than $200. With the help of the software you can process different types of images and thus output point clouds, determine areas or check volumes. You can export the data in different formats, so Metashape can often be combined with other programs. Especially interesting: 4D models can also be edited with this software.
Especially among beginners, the RealityCapture software from CapturingReality has been able to establish a good reputation. This is mainly due to the simple user interface. Compared to many competitors, the design is much clearer and enables intuitive operation even for newcomers. The offer is nevertheless extensive. For example, you can create georeferenced maps, 3D mesh structures, virtual reality scenes or similar with your images. Another advantage is that the software can be used with laser scans without any problems. In addition, the costs for the Codes Targets are at an inexpensive level of less than ten euros.
Regard3D also appears in our list. And there are several good reasons for that. On the one hand, it is an open source solution that you can use completely free of charge. In addition, updates and innovations are regularly brought to the market, for which Regard also usually provides extensive instructions and tutorials. Regard3D is also referred to as a Structure-From-Motion program. This means that photos from different angles can be converted into a 3D model. Regard3D can be used on different platforms such as Linux, Windows or OS X. In addition, you can use various third-party tools.
PhotoModeler, as photogrammetry software, is especially good for use with photos taken with your own smartphone. The program specializes in CAD and CNC manufacturing and offers a comparatively inexpensive way to perform 3D measurements. The software provides different methods within the application and allows you, for example, to manually match images as well as to create models from coded targets. PhotoModeler also offers you great flexibility in terms of price. Besides a premium version and a standard version, you can also purchase an additional add-on for processing 2D patterns for the latter.
Application of photogrammetry
Photogrammetry is a technique used in various industries and directions. Mostly when a scanning system would be too time-consuming or cost-intensive. The versatility of photogrammetry ensures that it can be used on larger projects as well as smaller ones. This makes it easy to create topographic maps or create large models for shipbuilding. Alternatively, however, the application is also possible in smaller scales, for example for models of vehicles. Other typical fields of application are land surveying, engineering or architecture.
Advantages and disadvantages
- Fast and precise procedure
- Flexible and simple, as only one digital measuring camera is required
- Texture of the objects well recognizable
- Recording movements possible
- Measurement on transparent and reflective surfaces not without problems