Accuracy of Unmanned Aerial Systems Photogrammetry and Structure from Motion in Surveying and Mapping: A Review

Highly detailed topographic surveying at minimal cost and effort has always been one of the developing areas of scientific interest. Image-based remote sensing solutions using unmanned aerial systems (UAS) and structure from motion (SfM) with multi-view stereo (MVS) photogrammetry are the latest automation and advancement in surveying engineering that provides high-resolution topographic data. Although recent developments have led to the extensive use of UAS-SfM in mapping applications, the only concern that remains is the UAS-based survey accuracy; is this method accurate enough to be used in surveying and mapping applications as an alternative to conventional methods? Evaluation of accuracy and validation of products before they can be applied to a real-world problem is a prerequisite for any emerging technology. Recently, there has been a proliferation of accuracy assessment and validation studies of UAS-SfM-based surveying. However, quantitative validation studies are slightly different, and the accuracy of each study is significantly different from another. The true limits of this technique can only be revealed by assembling a large dataset from previous individual studies. This study was motivated by the lack of such quantitative analysis. This study gives an overview of UAS and SfM, discusses the major factors that influence the accuracy, and presents a synthesis of the recent validation studies conducted quantitative assessments of UAS-SfM-derived digital elevation datasets, and thereby demonstrates the accuracy and limitation of UAS-SfM -based topographic surveying.