Articles | Volume 1, issue 2
https://doi.org/10.5194/soil-1-583-2015
https://doi.org/10.5194/soil-1-583-2015
Original research article
 | 
27 Aug 2015
Original research article |  | 27 Aug 2015

SF3M software: 3-D photo-reconstruction for non-expert users and its application to a gully network

C. Castillo, M. R. James, M. D. Redel-Macías, R. Pérez, and J. A. Gómez

Abstract. Three-dimensional photo-reconstruction (PR) techniques have been successfully used to produce high-resolution surface models for different applications and over different spatial scales. However, innovative approaches are required to overcome some limitations that this technique may present for field image acquisition in challenging scene geometries. Here, we evaluate SF3M, a new graphical user interface for implementing a complete PR workflow based on freely available software (including external calls to VisualSFM and CloudCompare), in combination with a low-cost survey design for the reconstruction of a several-hundred-metres-long gully network. SF3M provided a semi-automated workflow for 3-D reconstruction requiring ~ 49 h (of which only 17 % required operator assistance) for obtaining a final gully network model of > 17 million points over a gully plan area of 4230 m2. We show that a walking itinerary along the gully perimeter using two lightweight automatic cameras (1 s time-lapse mode) and a 6 m long pole is an efficient method for 3-D monitoring of gullies, at a low cost (~ EUR 1000 budget for the field equipment) and the time requirements (~ 90 min for image collection). A mean error of 6.9 cm at the ground control points was found, mainly due to model deformations derived from the linear geometry of the gully and residual errors in camera calibration. The straightforward image collection and processing approach can be of great benefit for non-expert users working on gully erosion assessment.

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Short summary
- We present SF3M, a new graphical user interface for implementing a complete 3-D photo-reconstruction workflow based on freely available software, in combination with a low-cost survey design for the reconstruction of a several-hundred-metres-long gully network. - This methodology implied using inexpensive means, little manpower, in a short time span, being a promising tool for gully erosion evaluation in scenarios with demanding budget and time constraints and reduced operator expertise.