Very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform

Abstract

Version disponible sur Internet : [ http://dx.doi.org/10.1002/esp.1595 ]<br />Journal ArticleInternational audienceThe increasing availability of aerial photography and satellite imagery offers new possibilities for characterizing river morphology. The precision of new very high resolution (VHR) images allows smaller scale objects within river corridors to be studied. High survey frequencies provide increased opportunities for the monitoring of river restoration.Following this evolution in platform technology, a small radio-controlled motorized vehicle flying at low altitude was used to study both channel water depth and gravel bar geometry. The VHR imagery provided by this equipment allowed both channel bathymetry and a high accuracy photogrammetric digital elevation model (DEM) to be realized. Using case studies from the Ain and the Drôme Rivers in France, the accuracy of the results is presented and the various challenges associated with the new platform are discussed. One significant issue is that due to the low elevation of the survey the coverage of a target area is usually based on several photographs, which leads to variations in illumination conditions that stem from atmospheric changes. The images were processed to minimize this source of error but a number of issues have yet to be resolved.Bathymetric models with R2 values between 0·59 and 0·90 were created in spite of the lack of channel bed homogeneity at the various sites. The gravel bar was also effectively mapped, and the photogrammetrically predicted DEM provided a 5-10 cm pixel resolution with a vertical precision between 2 and 40 cm according to the position within the image. This paper shows that, despite unstable image acquisition, unmanned radio-controlled platforms provide significant advantages for the study of river processes, offering a flexible very high resolution data source for both channel bathymetry and gravel bar topography. Copyright ©2007 John Wiley & Sons, Ltd

Technical note: Bathymetry observations of inland water bodies using a tethered single-beam sonar controlled by an unmanned aerial vehicle

“…Bathymetry studies using UAVs are so far restricted to (i) spectral signature-depth correlation based on passive optical imagery (Flener et al, 2013;Lejot et al, 2007) or (ii) DEM (digital elevation model) generation through stereoscopic techniques from through-water pictures, correcting for the refractive index of water (Bagheri et al, 2015;Dietrich, 2016;Tamminga et al, 2014;Woodget et al, 2015).…”

Reach Scale Application of Uav+sfm Method in Shallow Rivers Hyperspatial Bathymetry

“…The aforementioned algorithm may be reliable for flow depths less than 0.7 m based on woodget et al study (2015). The spectral-depth relationship method might be used to correct the refraction effect in submerged regions for flow depths from 0.7 m to 1 m. However, more rtkGNSS and depth data points are required in this method and the results are site-specific and might be affected by scene illumination, flow and substrate condition as well (Lejot et al, 2007).…”

Modern comprehensive approach to monitor the morphodynamic evolution of a restored river corridor

“…3e), which has been equipped with the same type of high resolution digital camera and with a GPS for more convenient geo-referencing. The paraglider has been used to detect important morphologic changes, similar to what was shown by Lejot et al (2007) soon after a flood occurred and without waiting for the annual airborne LIDAR flight. Using both image sets we have thus been able to test and improve several techniques based on pattern recognition analysis to calibrate both hydraulics and ecosystem models Perona et al, 2009a).…”