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1

Optimising UAV Data Acquisition and Processing for Photogrammetry: A Review

Pargieła Karolina

Geomatics and Environmental Engineering

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2023

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Vol. 17, no. 3

29--59

EN

Unmanned aerial vehicles (UAVs) are used to acquire measurement data for an increasing number of applications. Photogrammetric studies based on UAV data, thanks to the significant development of computer vision techniques, photogrammetry, and equipment miniaturization, allow sufficient accuracy for many engineering and non-engineering applications to be achieved. In addition to accuracy, development time and cost of data acquisition and processing are also important issues. The aim of this paper is to present potential limitations in the use of UAVs to acquire measurement data and to present measurement and processing techniques affecting the optimisation of work both in terms of accuracy and economy. Issues related to the type of drones used (multi-rotor, fixed-wing), type of shutter in the camera (rolling shutter, global shutter ), camera calibration method (pre-calibration, self-calibration), georeferencing method (direct, indirect), technique of measuring the external images orientation parameters (RTK, PPK, PPP), flight design methods and the type of software used were analysed.

2

Vehicle detection and masking in UAV images using YOLO to improve photogrammetric products

Pargieła Karolina

Reports on Geodesy and Geoinformatics

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2022

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Vol. 114

15--23

EN

Photogrammetric products obtained by processing data acquired with Unmanned Aerial Vehicles (UAVs) are used in many fields. Various structures are analysed, including roads. Many roads located in cities are characterised by heavy traffic. This makes it impossible to avoid the presence of cars in aerial photographs. However, they are not an integral part of the landscape, so their presence in the generated photogrammetric products is unnecessary. The occurrence of cars in the images may also lead to errors such as irregularities in digital elevation models (DEMs) in roadway areas and the blurring effect on orthophotomaps. The research aimed to improve the quality of photogrammetric products obtained with the Structure from Motion algorithm. To fulfil this objective, the Yolo v3 algorithm was used to automatically detect cars in the images. Neural network learning was performed using data from a different flight to ensure that the obtained detector could also be used in independent projects. The photogrammetric process was then carried out in two scenarios: with and without masks. The obtained results show that the automatic masking of cars in images is fast and allows for a significant increase in the quality of photogrammetric products such as DEMs and orthophotomaps.

3

Orientation and Pose estimation for Panoramic Imagery

Laganiere R., Kangni F.

Machine Graphics and Vision

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2010

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Vol. 19, No. 3

339-363

EN

In a database of geo-referenced images, determining the exact position of each panorama is an important step in order to ensure the consistency of visual information. This paper addresses the problem of camera pose recovery from spherical (360°) panoramas. The 3D information is extracted from a database of panoramic images sparsely distributed over a scene of interest. We present a two-stage algorithm to recover the position of omni-directional cameras using pair wise essential matrices. First, all rotations with respect to the world frame are found using an incremental bundle adjustment procedure, thus achieving what we call panorama alignment. Full camera positions are then computed using bundle adjustment. During this step, the previously computed panorama orientations, used to feed the global optimization process, can be further refined. Results are shown for indoor and outdoor panorama sets.

4

Application of modal analysis supported by 3D vision-based measurements

Kohut P., Kurowski P.

Journal of Theoretical and Applied Mechanics

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2009

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Vol. 47 nr 4

855-870

EN

In the paper, applications of the 3D vision techniques to the modal analysis method are presented. The goal of the project was to develop a methodology for vibration amplitude measurements and a software tool for modal analysis based on visual data. For this purpose, dedicated procedures and algorithms based on the vision technique methods were developed. 3D measurements of vibrations and structure geometry were obtained by application and developing passive 3D vision techniques.The amplitude of vibrations was calculated for selected points on thestructure. Necessary vision data were received from the high-speed digital camera ”X-Stream Vision” in form of ”avi” files that were used as the input data for the developed software tool. The amplitude of vibration displacements obtained from vision-based measurements were treated as the input data for operational modal analysis algorithms. In this domain, the Balanced Realization algorithm has been used.

PL

W artykule zaprezentowano wykorzystanie trójwymiarowych technik wizyjnych w metodach analizy modalnej. Przedstawiono opracowaną metodykę pomiarów amplitudy drgań oraz narzędzie programowe do realizacji analizy modalnej bazującej na danych wizyjnych. Opracowano dedykowane procedury i algorytmy wykorzystujące metody wizyjne. Amplituda drgań została obliczona w wybranych punktach pomiarowych struktury. Trójwymiarowe pomiary drgań oraz geometrię struktury uzyskano poprzez zastosowanie i opracowanie trójwymiarowych pasywnych metod wizyjnych. Jako dane wejściowe do opracowanego narzędzia programowego użyto sygnały wizyjne otrzymane z „szybkiej” kamery cyfrowej X-StreamVision w postaci plików ’avi’. Uzyskana z systemu wizyjnego amplituda drgań stanowiła dane wejściowe do algorytmu operacyjnej analizy modalnej. W tej dziedzinie wykorzystany został algorytm zbilansowanej realizacji (ang. Balanced Realization).

5

Zastosowanie trójwymiarowych technik wizyjnych do pomiaru i analizy drgań

Kohut P., Kurowski P.

Diagnostyka

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2007

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nr 3(43)

55-63

PL

Obecnie dużą wagę przywiązuje się do nowoczesnych bezstykowych metod pomiaru drgań mechanicznych. Mogą być tutaj wykorzystywane różne techniki, np. magnetyczne, laserowe, wizyjne, akustyczne. W prezentowanym artykule autorzy skupiają się na wykorzystaniu technik wizyjnych, a w szczególności na zastosowaniu metody struktury z ruchu do pomiaru i analizy drgań. Na bazie dekompozycji na wartości osobliwe zostały opracowane i zaimplementowane ich różne modele: prostopadły, prostopadły skalowany oraz para-perspektywiczny. Amplituda drgań jest wyznaczana dla wybranych punktów pomiarowych analizowanego obiektu. Każdy punkt reprezentowany jest przy pomocy znacznika montowanego na konstrukcji. W artykule zawarto rozważania teoretyczne dotyczące omawianych metod, ich weryfikację na podstawie danych symulacyjnych oraz wstępne testy eksperymentalne.

EN

At present time they attach importance to modern non-contact methods of mechanical vibration measurements. There can be used various techniques, e.g.: magnetic, laser, visual, and acoustics. In the paper authors concentrate in application of vision techniques: structure from motion for vibration measurement and analysis in particular. There were developed and implemented various models: orthographic, scaled orthographic and para-perspective on the basis of singular value decomposition method. Amplitude of vibration was calculated for selected measurement points of analysed object. Each measurement point was represented by means of marker mounted on a construction. In the paper theoretical considerations of mentioned methods and verification based on simulation data as well as initial experimental tests were discussed.

6

3D measurements and motion analysis supported by passive vision techniques

Kohut P.

Computer Assisted Mechanics and Engineering Sciences

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2007

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Vol. 14, No. 4

637-649

EN

The article contains presentation of application of three-dimensional vision methods in realization of vibration measurements and their analysis. For this purpose algorithms were developed of discrete epipolar geometry and structure from motion, with the usage of one camera. Vibration amplitude is determined for selected measurement points on the analyzed object. Each point is represented by flat or three-dimensional marker attached on a construction. The article includes algorithms of the discussed methods and verification of those methods based upon simulation data, as we as preliminary experimental tests carried out on a test bed.

7

Sequential projective reconstruction with factorization

Xu X., Harada K.

Machine Graphics and Vision

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2003

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Vol. 12, No. 4

477-487

EN

The objective of the present study is to propose a new sequential projective factorization approach for recovering the structure and motion. In contrast to the previous sequential factorization methods or nonlinear filter methods, it starts with the first two images and the accurate result can be obtained even for the first image pair without considering provision of a reliable initial estimation. In each recursive step, the infinite sequences can be effectively handled while keeping the size of the factorization matrix unchanged. The experimental data in the paper show that sufficient accuracy can be attained with absence of noise.

8

Integration for 3D structure / motion estimation based on line drawings

Yang L., Sahli H.

Machine Graphics and Vision

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2000

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Vol. 9, No. 1/2

251-261

EN

A general framework for 3D structure / motion analysis is proposed upon integration of different visual modules. Line drawings are analyzed from motion point of view, and provide an effective means for 3D reconstruction. 2D motion based and feature correspondences based approaches are efficiently integrated with the line drawing interpretations under our framework. Normal flow of line segment is employed here to characterize 2D motion and the finite difference method is used for its estimation in a simple and practical way. To implement the proposed integration model, an incremential scheme is developed ti estimate 3D structure / motion from a sequence of images. Experiments on scenes containing polyhedral objects demonstrate the feasibility of the proposed scheme, and show that the integration of different visual modules gives better 3D structure / motion estrimations.