Time lapse structure‐from‐motion photogrammetry for continuous geomorphic monitoring

Abstract

Recent advances are made in earth surface reconstruction with high spatial resolution due to SfM photogrammetry. High flexibility of data acquisition and high potential of process automation allows for a significant increase of the temporal resolution, as well, which is especially interesting to assess geomorphic changes. Two case studies are presented where 4D reconstruction is performed to study soil surface changes at 15 seconds intervals: (a) a thunderstorm event is captured at field scale and (b) a rainfall simulation is observed at plot scale. A workflow is introduced for automatic data acquisition and processing including the following approach: data collection, camera calibration and subsequent image correction, template matching to automatically identify ground control points in each image to account for camera movements, 3D reconstruction of each acquisition interval, and finally applying temporal filtering to the resulting surface change models to correct random noise and to increase the reliability of the measurement of signals of change with low intensity. Results reveal surface change detection with cm‐ to mm‐accuracy. Significant soil changes are measured during the events. Ripple and pool sequences become obvious in both case studies. Additionally, roughness changes and hydrostatic effects are apparent along the temporal domain at the plot scale. 4D monitoring with time‐lapse SfM photogrammetry enables new insights into geomorphic processes due to a significant increase of temporal resolution. Copyright © 2017 John Wiley & Sons, Ltd.

Measuring Change Using Quantitative Differencing of Repeat Structure-From-Motion Photogrammetry: The Effect of Storms on Coastal Boulder Deposits

“…The 2017 images required very little adjustment, but the corrections were essential for the 2015 GoPro images, which had strong barrel (or "fisheye" distortion). More complex and sophisticated lens correction techniques exist [41,54,[115][116][117][118] but Adobe's lens profiles have been tested and recommended in the photogrammetric literature [64,[119][120][121][122]. The quality of Lightroom's corrections are evident in before-and-after images ( Figure 6), and in the quality of the final model.…”

“…The swiftness with which researchers have embraced and applied this relatively new technology speaks to its inherent potential-UAV mapping is ideal for repeat low-cost, high-resolution data collection [41]-but also reflects rapid advances in the efficiency and stability of UAVs, the usability and reliability of controller software, and the sophistication of automated photogrammetric image processing [42][43][44][45].…”

Time‐Lapse Photogrammetry of Distributed Snow Depth During Snowmelt

“…Within the last few years, we counted at least six reports of time-lapse photogrammetry studies for geomorphological processes presented in articles or conferences (Abou Chakra et al, 2017;Eltner et al, 2017;Galland et al, 2016;James & Robson, 2014;Kromer et al, 2016;Mallalieu et al, 2017). From the most comprehensive ones, the main key point of success for this method is to define accurately ground control points (GCPs) within the scene of interest and identify them in the subsequent images.…”

Evaluating Image Tracking Approaches for Surface Velocimetry With Thermal Tracers

“…Taking data acquisition scheme and camera self‐calibration into consideration, object coordinates of the control points are retrieved from overlapping images using scale information and bundle adjustment. Its suitability to retrieve local GCP coordinates has been demonstrated by Eltner et al (). The resulting GCP accuracy is within subcentimeter range.…”