Virtual Only

3-Close-Range Photogrammetry

Dr. Angela D. Allen (University of North Carolina at Charlotte)

Friday, November 10, 2023
1:30 PM – 5:30 PM (EST USA)

Photogrammetry refers to the use of 2D images to acquire 3D dimensional information. The concept of using images for mapping dates back to the mid 1800’s but the potential wasn’t demonstrated for another 50 years. Early applications focused on mapping terrain, initially terrestrial (images taken from the ground) and then areal (images taken from air). Terrestrial photogrammetry, also known as close range photogrammetry, means ground-based applications with the distance between the camera and object ranging from 1 to 300 m. Close range (vs. terrestrial) tends to refer to measurements of objects rather than terrain. The applications have grown dramatically in recent decades with advances in digital cameras, computing power, and computer science, and now can deliver 3D measurements spanning a range of low-to-high measurement uncertainty. At the precision engineering end of the spectrum, state-of-the-art target-based photogrammetry systems can realize dimensional measurements at a level of parts in 10⁶ under ideal conditions. At the other limit, less accurate feature-based photogrammetry using inexpensive, e.g. cell phone, cameras can reach uncertainties at the level of parts in 10³-10⁴. Photogrammetry image processing software and apps are now readily available – in some cases free – and this has led to an explosion of applications from reverse engineering, architecture, forensics, mining, archeology, entertainment, and more. This tutorial describes target and feature-based photogrammetry at the appropriate technical level to enable an engineer unfamiliar with the technique to consider this inexpensive and accessible method for their next 3D measurement project.

Tutorial Outline:

1. Photogrammetry overview
2. Applications in manufacturing
3. The underlying mathematical principle
4. The role of the camera
5. Implementation of target-based photogrammetry
6. Feature-based photogrammetry
7. Implementation of feature-based photogrammetry
8. Approaches for evaluating measurement uncertainty

Dr. Allen’s research at UNC Charlotte focuses on dimensional metrology over a range of uncertainty limits and length scales, using a variety of techniques. She has worked onphotogrammetry-based research projects over the past 15 years, with a focus on unconventional applications and investigating uncertainty.^1-4

^1.“Low-Cost AR-Based Dimensional Metrology for Assembly”, Rahma Nawab and Angela Davies Allen, Machines, 10, No. 4, 243, 2022.

^2. “Optically Projected Length Scale for Use in Photogrammetry”, Patrick Thewlis, Ph.D. Dissertation, UNC Charlotte, May 2020.

^3. “Using 3D optical simulation to investigate uncertainty in image-based measurements,” Yue Dong, et.al, Optical Engineering, 53, 092007-1 –
092007-7, 2014.

^4. “Positioning Sensor by Combining Photogrammetry, Optical Projection and a Virtual Camera Model,” Benrui Zheng, et.al, Measurement
Science and Technology, 24, 105106-105114, 2013.