How Photogrammetric Software Works: A Perspective Based on UAV’s Exterior Orientation Parameters

Abstract

Earlier conventional photogrammetric techniques were used in the topographic mapping using a large format digital camera known as aerial photogrammetry. Recent advancements in UAV technology for photogrammetric purposes have provided a necessity of state-of-the-art photogrammetric software for processing images acquired using UAV. These so-called drones come with an inbuilt GPS and IMU system to geotag the image at the time of acquisition. This information is saved as EXIF data inside the image. There are software programs that provide an end-to-end solution for processing photogrammetric data (UAV-acquired images). This software has the capability of processing data with or without EXIF data. The study provides information related to various camera calibration parameters inside the UAV, and if an externally installed RTK could be useful in generating more accurate deliverables using photogrammetric processing. In UAVs, exterior orientation or EO are saved in both aircraft as well as in gimbal, so through this research, it was tried to look into in-depth of all the black box processes that are going on in the software. This study also provides a solution to the accuracy problems with the UAV-based photogrammetric survey methods.