2020 |
Verykokou, Styliani; Ioannidis, Charalabos Exterior orientation estimation of oblique aerial images using SfM-based robust bundle adjustment Journal Article In: Int. J. Remote Sens., vol. 41, no. 18, pp. 7233–7270, 2020, ISSN: 0143-1161. Abstract | Links | BibTeX | Tags: aerial triangulation, exterior orientation, oblique aerial images, Photogrammetry, structure from motion @article{Verykokou2020,In this article, a structure from motion (SfM) framework for oblique aerial images of man-made environments is proposed, covering the issues of determining overlapping images, feature extraction, image matching, rejection of erroneous correspondences, feature tracking, automatic transfer of ground control points (GCPs), and bundle block adjustment. One of the challenges that it is intended to solve is the reduction of the required manual work concerning the measurement of GCPs, in order to increase the degree of automation of the exterior orientation estimation process, through the usage of geometric constraints automatically imposed. Yet another challenge is the difficulty in matching correctly feature points among multiple oblique views that depict scenes with repetitive patterns and homogeneous textures. The proposed algorithm solves this by eliminating all erroneous tie points through the combination of multiple checks and geometric constraints imposed during the image matching procedure and a robust iterative bundle adjustment framework. The proposed SfM methodology is applied in different configurations of oblique images under non-ideal aerial triangulation scenarios characterized by lack of well-distributed GCPs as well as minimum manual image measurements. The results are analysed, focusing on the improvement of the accuracy of the exterior orientation parameters thanks to the proposed robust out-lier removal technique as well as on the impact of the proposed scale-based weighting strategy for bundle adjustment of oblique images on the exterior orientation results. The proposed SfM framework proves to be a good alternative solution to existing commercial SfM methods. ARTICLE HISTORY |
2018 |
Verykokou, Styliani; Ioannidis, Charalabos A PHOTOGRAMMETRY-BASED STRUCTURE FROM MOTION ALGORITHM USING ROBUST ITERATIVE BUNDLE ADJUSTMENT TECHNIQUES Journal Article In: ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci., vol. IV-4/W6, pp. 73–80, 2018, ISSN: 2194-9050. Abstract | Links | BibTeX | Tags: Bundle Adjustment, Coplanar Feature Points, exterior orientation, Homography, Oblique Images, structure from motion, Template Matching @article{Verykokou2018,Abstract. The purpose of this paper is the presentation of a novel algorithm for automatic estimation of the exterior orientation parameters of image datasets, which can be applied in the case that the scene depicted in the images has a planar surface (e.g., roof of a building). The algorithm requires the measurement of four coplanar ground control points (GCPs) in only one image. It uses a template matching method combined with a homography-based technique for transfer of the GCPs in another image, along with an incremental photogrammetry-based Structure from Motion (SfM) workflow, coupled with robust iterative bundle adjustment methods that reject any remaining outliers, which have passed through the checks and geometric constraints imposed during the image matching procedure. Its main steps consist of (i) determination of overlapping images without the need for GPS/INS data; (ii) image matching and feature tracking; (iii) estimation of the exterior orientation parameters of a starting image pair; and (iv) photogrammetry-based SfM combined with iterative bundle adjustment methods. A developed software solution implementing the proposed algorithm was tested using a set of UAV oblique images. Several tests were performed for the assessment of the errors and comparisons with well-established commercial software were made, in terms of automation and correctness of the computed exterior orientation parameters. The results show that the estimated orientation parameters via the proposed solution have comparable accuracy with those ones computed through the commercial software using the highest possible accuracy settings; in addition, double manual work was required by the commercial software compared to the proposed solution. |
2020 |
Exterior orientation estimation of oblique aerial images using SfM-based robust bundle adjustment Journal Article In: Int. J. Remote Sens., vol. 41, no. 18, pp. 7233–7270, 2020, ISSN: 0143-1161. |
2018 |
A PHOTOGRAMMETRY-BASED STRUCTURE FROM MOTION ALGORITHM USING ROBUST ITERATIVE BUNDLE ADJUSTMENT TECHNIQUES Journal Article In: ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci., vol. IV-4/W6, pp. 73–80, 2018, ISSN: 2194-9050. |