Skip to main content
ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #336637
Title: Fine-resolution repeat topographic surveying of dryland landscapes using UAS-based structure-from-motion photogrammetry: Assessing accuracy and precision against traditional ground-based erosion measurements

Author
item GILLAN, JEFFREY - New Mexico State University
item Karl, Jason
item ELAKSER, AHMED - Non ARS Employee
item DUNIWAY, MICHAEL - Us Geological Survey (USGS)

Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2017
Publication Date: 5/3/2017
Publication URL: http://handle.nal.usda.gov/10113/5931518
Citation: Gillan, J.K., Karl, J.W., Elakser, A., Duniway, M.C. 2017. Fine-resolution repeat topographic surveying of dryland landscapes using UAS-based structure-from-motion photogrammetry: Assessing accuracy and precision against traditional ground-based erosion measurements. Remote Sensing. 9:437.

Interpretive Summary: With the increasing availability and decreasing cost of unmanned aerial systems (UAS, or drones) for collecting high-resolution aerial photography, new tools are needed for translating UAS-based image products into measurements of dryland ecosystems in an accurate and cost-effectdive manner. We compared the accuracy and repeatability of soil surface measurements from UAS imagery using structure-from-motion (SfM) digital photogrammetry to ground-based measurements of soil elevations and soil surface change made by large erosion bridges. We found strong agreement (accuracy) between the image-based photogrammetric method of estimating soil surface elevation and elevations taken from the erosion bridges (between 2.9cm and 3.0cm RMSE). Repeatability of measurements over time was also high (2.7 to 2.8cm RMSE between image sets taken on different dates). These results suggest that new technologies in UAS and digital photogrammetry can help improve measurements of soil surface change over large landsdcapes comapred to labor-intensive field methods restricted to a few point locations. This could help increase our understanding of soil loss and movement patterns over large landscapes.

Technical Abstract: Structure-from-motion (SfM) photogrammetry from unmanned aircraft system (UAS) imagery is an emerging tool for repeat topographic surveying of dryland erosion. These methods are particularly appealing due to the ability to cover large landscapes compared to field methods and at reduced costs and higher spatial resolution compared to airborne laser scanning. However, a systematic comparison between aerial SfM and ground-based methods at multiple points in time has not been investigated. Here we compare the measurement of topographic profiles between erosion bridges and very-high resolution digital elevation models (DEMs) reconstructed with SfM methods from a fixed-wing UAS. In addition to accuracy, we investigated the repeatability of the DEMs which determined the level of detectable change in a survey time-series. Finally, we tested the effect of ground control point (GCP) spacing and quantity on accuracy and precision of the DEMs. We found strong vertical agreement (accuracy) between the methods and virtually no differences using 12 GCPs (RMSE 2.9 cm) and 3 GCPs (RMSE 3.0 cm) to reconstruct DEMs. Vertical repeatability was found to have RMSE 2.7 cm using 12 GCPs and RMSE 2.8 cm using 3 GCPs. The results from repeat UAS imagery, SfM processing, and strong agreement and precision compared with ground-based measures here suggests these technologies can help increase our understanding of soil loss patterns over large landscapes. Applications of this method could include unpaved road network monitoring, compliance monitoring for oil and gas exploration and development, pipeline installation, and other land management challenges.