scholarly journals THE TEST FIELD FOR UAV ACCURACY ASSESSMENTS

2019 ◽  
Vol XLII-1/W2 ◽  
pp. 67-73
Author(s):  
P. Wiącek ◽  
K. Pyka
Keyword(s):  
Camera Calibration ◽  
Bundle Adjustment ◽  
Common Method ◽  
Data Sets ◽  
Test Field ◽  
Exterior Orientation ◽  
Multiple Factors ◽  
Adjustment Processes ◽  
Flight Direction ◽  
Accuracy Assessments

<p><strong>Abstract.</strong> Nowadays UAV photogrammetry becomes a common method for mapping and surveying. At the same time due to the increasing range of work carried out with UAV, the importance of final product accuracy increases. However to obtain survey-grade accuracy it is necessary to perform bundle adjustment processes that could be affected by multiple factors like unstable camera calibration, correlation between interior and exterior orientation and insufficient georeference information. One of the aims of the project was to prepare the terrestrial test field, which helps to obtain optimal decorrelation and allows to objectively assess the accuracy of the bundle adjustment in UAV application. During the project, two multi-variant flights over the test field were conducted. The flights were performed with a fixed-wing airframe equipped with PPK receiver on-board. Based on the conducted flights, many data sets have been prepared, which differ as follows: types of cameras, GSD, flight direction and georeferenced method.</p>

scholarly journals THE DATABASE FOR MULTIFACTORIAL UAV ACCURACY ASSESSMENTS

2020 ◽  
Vol XLIII-B5-2020 ◽  
pp. 163-172
Author(s):  
P. Wiącek
Keyword(s):  
Camera Calibration ◽  
Statistical Models ◽  
A Priori ◽  
Bundle Adjustment ◽  
Data Sets ◽  
Test Field ◽  
Exterior Orientation ◽  
Multiple Factors ◽  
Adjustment Processes ◽  
Accuracy Assessments

Abstract. Due to the increasing range of work carried out with UAV in recent years, the importance of final product accuracy appreciates. However, obtaining survey-grade accuracy requires to perform bundle adjustment processes that could be affected by multiple factors like unstable camera calibration, a correlation between interior and exterior orientation, insufficient georeferenced information, and software settings. During the project, multi-variant flight over the test field was conducted. The flights were performed with a fixed-wing airframe equipped with PPK receiver on-board. Based on the conducted flights, the database for multifactorial data sets has been prepared. The database containing hundreds of independent adjustment variants which differ as follows: georeferencing method, flight configuration, additional camera calibration corrections, tie points filtering, and a priori accuracy settings. The database allowed to investigate the separate influence of each factor on the final results using ANOVA statistical models.

scholarly journals CALIBRATING PHOTOGRAMMETRIC AIRBORNE CAMERA SYSTEMS WITH DIFFRACTIVE OPTICAL ELEMENTS

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1637-1642
Author(s):  
D. Dahlke ◽  
M. Geßner ◽  
H. Meißner ◽  
K. Stebner ◽  
D. Grießbach ◽  
...  
Keyword(s):  
Camera Calibration ◽  
Bundle Adjustment ◽  
Test Field ◽  
Diffractive Optical Elements ◽  
Camera Model ◽  
Camera System ◽  
Time Saving ◽  
Optical Elements ◽  
Camera Systems ◽  
Calibration Methods

<p><strong>Abstract.</strong> This paper presents a laboratory approach for geometric calibration of airborne camera systems. The setup uses an incoming laser beam, which is split by Diffractive Optical Elements (DOE) into a number of beams with precisely-known propagation directions. Each point of the diffraction pattern represents a point at infinity and is invariant against translation. A single image is sufficient to allow a complete camera calibration in accordance with classical camera calibration methods using the pinhole camera model and a distortion model. The presented method is time saving, since complex bundle adjustment procedures with several images are not necessary. It is well suited for the use with frame camera systems, but it works in principle also for pushbroom scanners. In order to prove the reliability, a conventional test field calibration is compared against the presented approach, showing that all estimated camera parameters are just insignificantly different. Furthermore a test flight over the Zeche Zollern reference target has been conducted. The aerotriangulation results shows that calibrating an airborne camera system with DOE is a feasible solution.</p>

scholarly journals Camera Calibration using the Damped Bundle Adjustment Toolbox

2014 ◽  
Vol II-5 ◽  
pp. 89-96 ◽  
Author(s):  
N. Börlin ◽  
P. Grussenmeyer
Keyword(s):  
Camera Calibration ◽  
Focal Length ◽  
Standard Procedure ◽  
Calibration Procedure ◽  
Bundle Adjustment ◽  
Data Sets ◽  
Calibration Data ◽  
Initial Values ◽  
Convergence Results ◽  
Highly Correlated

Camera calibration is one of the fundamental photogrammetric tasks. The standard procedure is to apply an iterative adjustment to measurements of known control points. The iterative adjustment needs initial values of internal and external parameters. In this paper we investigate a procedure where only one parameter &ndash; the focal length is given a specific initial value. The procedure is validated using the freely available Damped Bundle Adjustment Toolbox on five calibration data sets using varying narrow- and wide-angle lenses. <br><br> The results show that the Gauss-Newton-Armijo and Levenberg-Marquardt-Powell bundle adjustment methods implemented in the toolbox converge even if the initial values of the focal length are between 1/2 and 32 times the true focal length, even if the parameters are highly correlated. Standard statistical analysis methods in the toolbox enable manual selection of the lens distortion parameters to estimate, something not available in other camera calibration toolboxes. <br><br> A standardised camera calibration procedure that does not require any information about the camera sensor or focal length is suggested based on the convergence results. <br><br> The toolbox source and data sets used in this paper are available from the authors.

scholarly journals Extrinsic Camera Calibration with Line-Laser Projection

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1091
Author(s):  
Izaak Van Crombrugge ◽  
Rudi Penne ◽  
Steve Vanlanduit
Keyword(s):  
Camera Calibration ◽  
Real World ◽  
Large Scale ◽  
State Of The Art ◽  
Bundle Adjustment ◽  
Field Of View ◽  
Extrinsic Calibration ◽  
Practical Procedure ◽  
Partial Overlap

Knowledge of precise camera poses is vital for multi-camera setups. Camera intrinsics can be obtained for each camera separately in lab conditions. For fixed multi-camera setups, the extrinsic calibration can only be done in situ. Usually, some markers are used, like checkerboards, requiring some level of overlap between cameras. In this work, we propose a method for cases with little or no overlap. Laser lines are projected on a plane (e.g., floor or wall) using a laser line projector. The pose of the plane and cameras is then optimized using bundle adjustment to match the lines seen by the cameras. To find the extrinsic calibration, only a partial overlap between the laser lines and the field of view of the cameras is needed. Real-world experiments were conducted both with and without overlapping fields of view, resulting in rotation errors below 0.5°. We show that the accuracy is comparable to other state-of-the-art methods while offering a more practical procedure. The method can also be used in large-scale applications and can be fully automated.

scholarly journals Simultaneous Robot–World and Hand–Eye Calibration without a Calibration Object

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3949 ◽  
Author(s):  
Wei Li ◽  
Mingli Dong ◽  
Naiguang Lu ◽  
Xiaoping Lou ◽  
Peng Sun
Keyword(s):  
Three Dimensional ◽  
Real Data ◽  
Medical Robotics ◽  
Calibration Method ◽  
Bundle Adjustment ◽  
Data Sets ◽  
Rigid Transformation ◽  
Validation Experiment ◽  
Dimensional Reconstruction ◽  
Sparse Bundle Adjustment

An extended robot–world and hand–eye calibration method is proposed in this paper to evaluate the transformation relationship between the camera and robot device. This approach could be performed for mobile or medical robotics applications, where precise, expensive, or unsterile calibration objects, or enough movement space, cannot be made available at the work site. Firstly, a mathematical model is established to formulate the robot-gripper-to-camera rigid transformation and robot-base-to-world rigid transformation using the Kronecker product. Subsequently, a sparse bundle adjustment is introduced for the optimization of robot–world and hand–eye calibration, as well as reconstruction results. Finally, a validation experiment including two kinds of real data sets is designed to demonstrate the effectiveness and accuracy of the proposed approach. The translation relative error of rigid transformation is less than 8/10,000 by a Denso robot in a movement range of 1.3 m × 1.3 m × 1.2 m. The distance measurement mean error after three-dimensional reconstruction is 0.13 mm.

scholarly journals ESTIMATING EXTERIOR ORIENTATION PARAMETERS OF HYPERSPECTRAL BANDS BASED ON POLYNOMIAL MODELS

2017 ◽  
Vol XLII-3/W3 ◽  
pp. 19-25 ◽  
Author(s):  
A. Berveglieri ◽  
A. M. G. Tommaselli ◽  
E. Honkavaara
Keyword(s):  
Real Data ◽  
Bundle Adjustment ◽  
Time Dependent ◽  
Camera Model ◽  
Exterior Orientation ◽  
Spectral Bands ◽  
Acquisition Mode ◽  
Polynomial Models ◽  
Orientation Parameters ◽  
Sequential Acquisition

Hyperspectral camera operating in sequential acquisition mode produces spectral bands that are not recorded at the same instant, thus having different exterior orientation parameters (EOPs) for each band. The study presents experiments on bundle adjustment with time-dependent polynomial models for band orientation of hyperspectral cubes sequentially collected. The technique was applied to a Rikola camera model. The purpose was to investigate the behaviour of the estimated polynomial parameters and the feasibility of using a minimum of bands to estimate EOPs. Simulated and real data were produced for the analysis of parameters and accuracy in ground points. The tests considered conventional bundle adjustment and the polynomial models. The results showed that both techniques were comparable, indicating that the time-dependent polynomial model can be used to estimate the EOPs of all spectral bands, without requiring a bundle adjustment of each band. The accuracy of the block adjustment was analysed based on the discrepancy obtained from checkpoints. The root mean square error (RMSE) indicated an accuracy of 1&amp;thinsp;GSD in planimetry and 1.5&amp;thinsp;GSD in altimetry, when using a minimum of four bands per cube.

scholarly journals Calibration of Industrial Cameras for Aerial Photogrammetric Mapping

2020 ◽  
Vol 12 (19) ◽  
pp. 3130
Author(s):  
Jakub Kolecki ◽  
Przemysław Kuras ◽  
Elżbieta Pastucha ◽  
Krystian Pyka ◽  
Maciej Sierka
Keyword(s):  
Survey Methodology ◽  
Calibration Method ◽  
Bundle Adjustment ◽  
Test Field ◽  
Baseline Method ◽  
Field Calibration ◽  
Custom Software ◽  
Single Process ◽  
Industrial Cameras ◽  
Very High

This paper details the development of a camera calibration method purpose-built for use in photogrammetric survey production. The calibration test field was established in a hangar, where marker coordinates were measured using a high-precision survey methodology guaranteeing very high accuracy. An analytical model for bundle adjustment was developed that does not directly use the coordinates of field calibration markers but integrates bundle adjustment and survey observations into a single process. This solution, as well as a classical calibration method, were implemented in a custom software, for which the C++ source code repository is provided. The method was tested using three industrial cameras. The comparison was drawn towards a baseline method, OpenCV implementation. The results point to the advantages of using the proposed approach utilizing extended bundle adjustment.

scholarly journals Challenges in UAS-Based TIR Imagery Processing: Image Alignment and Uncertainty Quantification

2020 ◽  
Vol 12 (10) ◽  
pp. 1552 ◽  
Author(s):  
Veronika Döpper ◽  
Tobias Gränzig ◽  
Birgit Kleinschmit ◽  
Michael Förster
Keyword(s):  
Land Cover ◽  
Contrast Enhancement ◽  
Camera Calibration ◽  
Weather Conditions ◽  
Thermal Infrared ◽  
Temperature Correction ◽  
Image Alignment ◽  
Data Sets ◽  
Image Contrast Enhancement ◽  
The Impact

Thermal infrared measurements acquired with unmanned aerial systems (UAS) allow for high spatial resolution and flexibility in the time of image acquisition to assess ground surface temperature. Nevertheless, thermal infrared cameras mounted on UAS suffer from low radiometric accuracy as well as low image resolution and contrast hampering image alignment. Our analysis aims to determine the impact of the sun elevation angle (SEA), weather conditions, land cover, image contrast enhancement, geometric camera calibration, and inclusion of yaw angle information and generic and reference pre-selection methods on the point cloud and number of aligned images generated by Agisoft Metashape. We, therefore, use a total amount of 56 single data sets acquired on different days, times of day, weather conditions, and land cover types. Furthermore, we assess camera noise and the effect of temperature correction based on air temperature using features extracted by structure from motion. The study shows for the first time generalizable implications on thermal infrared image acquisitions and presents an approach to perform the analysis with a quality measure of inter-image sensor noise. Better image alignment is reached for conditions of high contrast such as clear weather conditions and high SEA. Alignment can be improved by applying a contrast enhancement and choosing both, reference and generic pre-selection. Grassland areas are best alignable, followed by cropland and forests. Geometric camera calibration hampers feature detection and matching. Temperature correction shows no effect on radiometric camera uncertainty. Based on a valid statistical analysis of the acquired data sets, we derive general suggestions for the planning of a successful field campaign as well as recommendations for a suitable preprocessing workflow.

scholarly journals GAUSSPY+: A fully automated Gaussian decomposition package for emission line spectra

2019 ◽  
Vol 628 ◽  
pp. A78 ◽  
Author(s):  
M. Riener ◽  
J. Kainulainen ◽  
J. D. Henshaw ◽  
J. H. Orkisz ◽  
C. E. Murray ◽  
...  
Keyword(s):  
Emission Line ◽  
Velocity Structure ◽  
Galactic Plane ◽  
Spatial Coherence ◽  
Large Data ◽  
Large Data Sets ◽  
Data Sets ◽  
Test Field ◽  
Data Set ◽  
Gaussian Decomposition

Our understanding of the dynamics of the interstellar medium is informed by the study of the detailed velocity structure of emission line observations. One approach to study the velocity structure is to decompose the spectra into individual velocity components; this leads to a description of the data set that is significantly reduced in complexity. However, this decomposition requires full automation lest it become prohibitive for large data sets, such as Galactic plane surveys. We developed GAUSSPY+, a fully automated Gaussian decomposition package that can be applied to emission line data sets, especially large surveys of HI and isotopologues of CO. We built our package upon the existing GAUSSPY algorithm and significantly improved its performance for noisy data. New functionalities of GAUSSPY+ include: (i) automated preparatory steps, such as an accurate noise estimation, which can also be used as stand-alone applications; (ii) an improved fitting routine; (iii) an automated spatial refitting routine that can add spatial coherence to the decomposition results by refitting spectra based on neighbouring fit solutions. We thoroughly tested the performance of GAUSSPY+ on synthetic spectra and a test field from the Galactic Ring Survey. We found that GAUSSPY+ can deal with cases of complex emission and even low to moderate signal-to-noise values.

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