Why is Photogrammetry Needed When Scanning Large Workpieces?

1. What is photogrammetry?

The term photogrammetry was coined by the Prussian architect Albrecht Meydenbauer, which appeared in his 1867 article "Die Photometrographie." It is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena.

There are many variants of photogrammetry. One example is the extraction of three-dimensional measurements from two-dimensional data (i.e., images); for example, the distance between two points that lie on a plane parallel to the photographic image plane can be determined by measuring their distance on the image if the scale of the image is known.

Nowadays, this kind of photogrammetry plays a vital role and is widely used in 3D scanning scanner, especially for the scanning of the large workpieces, it can help to improve the efficiency and accuracy dramatically.

2. Why is photogrammetry needed when scanning large workpieces?

The scanning of large workpieces has always been a problem for many manufactures, and the reason why is also obvious, it's too big. When using markers in 3D scanning system, the increase in times of marker jointing will lead to cumulative errors, thus leading to a low accuracy.

It is recommended to use the photogrammetry system when the size of the workpiece exceeds 1.5m and high precision measurement is required. Working with a 3D scanner, the photogrammetry system can help to decrease the cumulative error and improve the accuracy greatly.

3. How does photogrammetry work?

3.1 The working principle of photogrammetry

As mentioned in the first session, photogrammetry can extract 3D data from 2D images, So, by taking pictures of the workpiece in the reference distance, the markers on the surface can be captured, then the markers'coordinates will be calculated, which can be subsequently used in 3D scanning system. The accuracy of this marker data will be much higher than that of the markers captured by the 3D scanning scanner.

Photogrammetry Working Principle

3.2 The typical workflow of photogrammetry

• First, like the typical workflow of 3D scanning system, we need to place markers on the workpiece.

• Second, because the scale of the 2D images is required to extract 3D data from 2D images, we need to place a checking bar as the scale on or near the workpiece. The data of the checking bar is already known so the marker data can be calculated accordingly.

Checking Bar

• Third, taking pictures of the markers on the workpiece's surface from the center to the edges to cover the workpiece completely

• Last, input the pictures taken into 3D software and calculate the marker data for subsequent use.

4. How can ZG help?

To scan large workpieces with photogrammetry, ZG technology can provide different solutions according to different applications.

PhotoShot Lite is a professional photogrammetry system which is suitable for most of the large size workpieces like casting parts. It's portable and lightweight, and its volumetric accuracy can be up to 0.020mm/m.

PhotoShot Lite

PhotoShot Max is a wireless photogrammetry system which is suitable for extra-large objects like airplane, wind turbine blade, mining machine, etc. The accuracy can be up to 0.015mm/m, and with the WIFI 5G technology, PhotoShot Max can transmit the data wirelessly, the measuring range and efficiency can be improved dramatically.

PhotoShot Max

PhotoShot Max Taking Pictures

Besides the photogrammetry system, a suitable 3D scanner is also important for the scanning process. To improve the efficiency, we strongly recommend a 3D scanner with wide-range mode. Taking AtlaScan for example, its scanning area can be up to 600×550mm, which is definitely a better choice than normal 3D scanners.

AtlaScan Wide-range Mode

ZG Technology has been providing professional 3D solutions for over 8 years, not just for large workpieces, but all kinds of objects. We would love to offer you a solution for your application, talk to our experts today to find out more about 3D scanning technology and how they can have a long-lasting impact on your business.