Validation Tests of Open-Source Procedures for Digital Camera Calibration and 3d Image-Based Modelling

Toschi, I.; Rivola, Riccardo; Bertacchini, Eleonora; Castagnetti, Cristina; Dubbini, Marco; Capra, Alessandro

doi:10.5194/isprsarchives-xl-5-w2-647-2013

Cited by 7 publications

(4 citation statements)

References 19 publications

(12 reference statements)

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“…Digital elevation models (DEM) of the soil surface were obtained by means of close range digital photogrammetry software called Apero and MicMac v1.0.1 (IGN, Institut Géographique National, France; Ahmadabadian et al , ; Toschi et al , ). Images were taken on a monthly basis or more frequently in case of extreme rainfall events.…”

Section: Methodsmentioning

confidence: 99%

Evolution of overland flow connectivity in bare agricultural plots

Peñuela

Darboux

Javaux

et al. 2016

Earth Surf Processes Landf

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Soil surface roughness not only delays overland flow generation but also strongly affects the spatial distribution and concentration of overland flow. Previous studies generally aimed at predicting the delay in overland flow generation by means of a single parameter characterizing soil roughness. However, little work has been done to find a link between soil roughness and overland flow dynamics. This is made difficult because soil roughness and hence overland flow characteristics evolve differently depending on whether diffuse or concentrated erosion dominates. The present study examined whether the concept of connectivity can be used to link roughness characteristics to overland flow dynamics. For this purpose, soil roughness of three 30-m 2 tilled plots exposed to natural rainfall was monitored for two years. Soil micro-topography was characterized by means of photogrammetry on a monthly basis. Soil roughness was characterized by the variogram, the surface stream network was characterized by network-based indices and overland flow connectivity was characterized by Relative Surface Connection function (RSCf) functional connectivity indicator. Overland flow hydrographs were generated by means of a physically-based overland flow model based on 1-cm resolution digital elevation models. The development of eroded flow paths at the soil surface not only reduced the delay in overland flow generation but also resulted in a higher continuity of high flow velocity paths, an increase in erosive energy and a higher rate of increase of the overland flow hydrograph. Overland flow dynamics were found to be highly correlated to the RSCf characteristic points. By providing information regarding overland flow dynamics, the RSCf may thus serve as a quantitative link between soil roughness and overland flow generation in order to improve the overland flow hydrograph prediction. Elevation at the grid location (i, j) (mm) z(x)Elevation of the point x (mm)

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Section: Methodsmentioning

confidence: 99%

Evolution of overland flow connectivity in bare agricultural plots

Peñuela

Darboux

Javaux

et al. 2016

Earth Surf Processes Landf

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“…There are many studies describing the pre-calibration of digital cameras used for UAS mapping purposes during the last decade, and only a few with the camera mounted on a UAS and at a long object distance during calibration process. Some of them have been calibrated using planar calibration objects [13][14][15][16], some using a 3D target, but at short object distance [17][18][19], and only a few tested the impact of camera pre-calibration on UAS mapping projects [10,20].…”

Section: Related Workmentioning

confidence: 99%

3D Calibration Test-Field for Digital Cameras Mounted on Unmanned Aerial Systems (UAS)

2018

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Due to the large number of technological developments in recent years, UAS systems are now used for monitoring purposes and in projects with high precision demand, such as 3D model-based creation of dams, reservoirs, historical monuments etc. These unmanned systems are usually equipped with an automatic pilot device and a digital camera (photo/video, multispectral, Near Infrared etc.), of which the lens has distortions; but this can be determined in a calibration process. Currently, a method of “self-calibration” is used for the calibration of the digital cameras mounted on UASs, but, by using the method of calibration based on a 3D calibration object, the accuracy is improved in comparison with other methods. Thus, this paper has the objective of establishing a 3D calibration field for the digital cameras mounted on UASs in terms of accuracy and robustness, being the largest reported publication to date. In order to test the proposed calibration field, a digital camera mounted on a low-cost UAS was calibrated at three different heights: 23 m, 28 m, and 35 m, using two configurations for image acquisition. Then, a comparison was made between the residuals obtained for a number of 100 Check Points (CPs) using self-calibration and test-field calibration, while the number of Ground Control Points (GCPs) variedand the heights were interchanged. Additionally, the parameters where tested on an oblique flight done 2 years before calibration, in manual mode at a medium altitude of 28 m height. For all tests done in the case of the double grid nadiral flight, the parameters calculated with the proposed 3D field improved the results by more than 50% when using the optimum and a large number of GCPs, and in all analyzed cases with 75% to 95% when using a minimum of 3 GCP. In this context, it is necessary to conduct accurate calibration in order to increase the accuracy of the UAS projects, and also to reduce field measurements.

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“…A full review of camera calibration methods and models developed in the last few years can be found in [ 3 – 5 ] describing the commonly adopted methods such as Tsai [ 6 ] or Zhang [ 7 ]. These are all based on the pinhole camera model including terms for modeling radial distortion.…”

Section: Introductionmentioning

confidence: 99%

Calibration of Action Cameras for Photogrammetric Purposes

Balletti

Guerra

Tsioukas

et al. 2014

Sensors

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The use of action cameras for photogrammetry purposes is not widespread due to the fact that until recently the images provided by the sensors, using either still or video capture mode, were not big enough to perform and provide the appropriate analysis with the necessary photogrammetric accuracy. However, several manufacturers have recently produced and released new lightweight devices which are: (a) easy to handle, (b) capable of performing under extreme conditions and more importantly (c) able to provide both still images and video sequences of high resolution. In order to be able to use the sensor of action cameras we must apply a careful and reliable self-calibration prior to the use of any photogrammetric procedure, a relatively difficult scenario because of the short focal length of the camera and its wide angle lens that is used to obtain the maximum possible resolution of images. Special software, using functions of the OpenCV library, has been created to perform both the calibration and the production of undistorted scenes for each one of the still and video image capturing mode of a novel action camera, the GoPro Hero 3 camera that can provide still images up to 12 Mp and video up 8 Mp resolution.

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Validation Tests of Open-Source Procedures for Digital Camera Calibration and 3d Image-Based Modelling

Cited by 7 publications

References 19 publications

Evolution of overland flow connectivity in bare agricultural plots

Evolution of overland flow connectivity in bare agricultural plots

3D Calibration Test-Field for Digital Cameras Mounted on Unmanned Aerial Systems (UAS)

Calibration of Action Cameras for Photogrammetric Purposes

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