scholarly journals ORIENTATION OF OBLIQUE AIRBORNE IMAGE SETS – EXPERIENCES FROM THE ISPRS/EUROSDR BENCHMARK ON MULTI-PLATFORM PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B1 ◽  
pp. 185-191
Author(s):  
M. Gerke ◽  
F. Nex ◽  
F. Remondino ◽  
K. Jacobsen ◽  
J. Kremer ◽  
...  
Keyword(s):  
Digital Camera ◽  
Research Problem ◽  
Bundle Adjustment ◽  
Random Errors ◽  
Interest Points ◽  
Image Block ◽  
Point Matching ◽  
Camera Systems ◽  
Oblique Images ◽  
Image Orientation

During the last decade the use of airborne multi camera systems increased significantly. The development in digital camera technology allows mounting several mid- or small-format cameras efficiently onto one platform and thus enables image capture under different angles. Those oblique images turn out to be interesting for a number of applications since lateral parts of elevated objects, like buildings or trees, are visible. However, occlusion or illumination differences might challenge image processing. From an image orientation point of view those multi-camera systems bring the advantage of a better ray intersection geometry compared to nadir-only image blocks. On the other hand, varying scale, occlusion and atmospheric influences which are difficult to model impose problems to the image matching and bundle adjustment tasks. In order to understand current limitations of image orientation approaches and the influence of different parameters such as image overlap or GCP distribution, a commonly available dataset was released. The originally captured data comprises of a state-of-the-art image block with very high overlap, but in the first stage of the so-called ISPRS/EUROSDR benchmark on multi-platform photogrammetry only a reduced set of images was released. In this paper some first results obtained with this dataset are presented. They refer to different aspects like tie point matching across the viewing directions, influence of the oblique images onto the bundle adjustment, the role of image overlap and GCP distribution. As far as the tie point matching is concerned we observed that matching of overlapping images pointing to the same cardinal direction, or between nadir and oblique views in general is quite successful. Due to the quite different perspective between images of different viewing directions the standard tie point matching, for instance based on interest points does not work well. How to address occlusion and ambiguities due to different views onto objects is clearly a non-solved research problem so far. In our experiments we also confirm that the obtainable height accuracy is better when all images are used in bundle block adjustment. This was also shown in other research before and is confirmed here. Not surprisingly, the large overlap of 80/80% provides much better object space accuracy – random errors seem to be about 2-3fold smaller compared to the 60/60% overlap. A comparison of different software approaches shows that newly emerged commercial packages, initially intended to work with small frame image blocks, do perform very well.

scholarly journals ORIENTATION OF OBLIQUE AIRBORNE IMAGE SETS – EXPERIENCES FROM THE ISPRS/EUROSDR BENCHMARK ON MULTI-PLATFORM PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B1 ◽  
pp. 185-191 ◽  
Author(s):  
M. Gerke ◽  
F. Nex ◽  
F. Remondino ◽  
K. Jacobsen ◽  
J. Kremer ◽  
...  
Keyword(s):  
Digital Camera ◽  
Research Problem ◽  
Bundle Adjustment ◽  
Random Errors ◽  
Interest Points ◽  
Image Block ◽  
Point Matching ◽  
Camera Systems ◽  
Oblique Images ◽  
Image Orientation

During the last decade the use of airborne multi camera systems increased significantly. The development in digital camera technology allows mounting several mid- or small-format cameras efficiently onto one platform and thus enables image capture under different angles. Those oblique images turn out to be interesting for a number of applications since lateral parts of elevated objects, like buildings or trees, are visible. However, occlusion or illumination differences might challenge image processing. From an image orientation point of view those multi-camera systems bring the advantage of a better ray intersection geometry compared to nadir-only image blocks. On the other hand, varying scale, occlusion and atmospheric influences which are difficult to model impose problems to the image matching and bundle adjustment tasks. In order to understand current limitations of image orientation approaches and the influence of different parameters such as image overlap or GCP distribution, a commonly available dataset was released. The originally captured data comprises of a state-of-the-art image block with very high overlap, but in the first stage of the so-called ISPRS/EUROSDR benchmark on multi-platform photogrammetry only a reduced set of images was released. In this paper some first results obtained with this dataset are presented. They refer to different aspects like tie point matching across the viewing directions, influence of the oblique images onto the bundle adjustment, the role of image overlap and GCP distribution. As far as the tie point matching is concerned we observed that matching of overlapping images pointing to the same cardinal direction, or between nadir and oblique views in general is quite successful. Due to the quite different perspective between images of different viewing directions the standard tie point matching, for instance based on interest points does not work well. How to address occlusion and ambiguities due to different views onto objects is clearly a non-solved research problem so far. In our experiments we also confirm that the obtainable height accuracy is better when all images are used in bundle block adjustment. This was also shown in other research before and is confirmed here. Not surprisingly, the large overlap of 80/80% provides much better object space accuracy – random errors seem to be about 2-3fold smaller compared to the 60/60% overlap. A comparison of different software approaches shows that newly emerged commercial packages, initially intended to work with small frame image blocks, do perform very well.

scholarly journals CO-REGISTRATION OF TERRESTRIAL AND UAV-BASED IMAGES – EXPERIMENTAL RESULTS

2016 ◽  
Vol XL-3/W4 ◽  
pp. 11-18 ◽  
Author(s):  
M. Gerke ◽  
F. Nex ◽  
P. Jende
Keyword(s):  
Scale Space ◽  
Urban Environments ◽  
Bundle Adjustment ◽  
Image Block ◽  
Point Matching ◽  
Combined Use ◽  
Aerial Platforms ◽  
Automatic Matching ◽  
Nonlinear Scale ◽  
The Impact

For many applications within urban environments the combined use of images taken from the ground and from unmanned aerial platforms seems interesting: while from the airborne perspective the upper parts of objects including roofs can be observed, the ground images can complement the data from lateral views to retrieve a complete visualisation or 3D reconstruction of interesting areas. The automatic co-registration of air- and ground-based images is still a challenge and cannot be considered solved. The main obstacle is originating from the fact that objects are photographed from quite different angles, and hence state-of-the-art tie point measurement approaches cannot cope with the induced perspective transformation. One first important step towards a solution is to use airborne images taken under slant directions. Those oblique views not only help to connect vertical images and horizontal views but also provide image information from 3D-structures not visible from the other two directions. According to our experience, however, still a good planning and many images taken under different viewing angles are needed to support an automatic matching across all images and complete bundle block adjustment. Nevertheless, the entire process is still quite sensible – the removal of a single image might lead to a completely different or wrong solution, or separation of image blocks. <br><br> In this paper we analyse the impact different parameters and strategies have on the solution. Those are a) the used tie point matcher, b) the used software for bundle adjustment. Using the data provided in the context of the ISPRS benchmark on multi-platform photogrammetry, we systematically address the mentioned influences. Concerning the tie-point matching we test the standard SIFT point extractor and descriptor, but also the SURF and ASIFT-approaches, the ORB technique, as well as (A)KAZE, which are based on a nonlinear scale space. In terms of pre-processing we analyse the Wallis-filter. Results show that in more challenging situations, in this case for data captured from different platforms at different days most approaches do not perform well. Wallis-filtering emerged to be most helpful especially for the SIFT approach. The commercial software pix4dmapper succeeds in overall bundle adjustment only for some configurations, and especially not for the entire image block provided.

scholarly journals CO-REGISTRATION OF TERRESTRIAL AND UAV-BASED IMAGES – EXPERIMENTAL RESULTS

2016 ◽  
Vol XL-3/W4 ◽  
pp. 11-18
Author(s):  
M. Gerke ◽  
F. Nex ◽  
P. Jende
Keyword(s):  
Scale Space ◽  
Urban Environments ◽  
Bundle Adjustment ◽  
Image Block ◽  
Point Matching ◽  
Combined Use ◽  
Aerial Platforms ◽  
Automatic Matching ◽  
Nonlinear Scale ◽  
The Impact

For many applications within urban environments the combined use of images taken from the ground and from unmanned aerial platforms seems interesting: while from the airborne perspective the upper parts of objects including roofs can be observed, the ground images can complement the data from lateral views to retrieve a complete visualisation or 3D reconstruction of interesting areas. The automatic co-registration of air- and ground-based images is still a challenge and cannot be considered solved. The main obstacle is originating from the fact that objects are photographed from quite different angles, and hence state-of-the-art tie point measurement approaches cannot cope with the induced perspective transformation. One first important step towards a solution is to use airborne images taken under slant directions. Those oblique views not only help to connect vertical images and horizontal views but also provide image information from 3D-structures not visible from the other two directions. According to our experience, however, still a good planning and many images taken under different viewing angles are needed to support an automatic matching across all images and complete bundle block adjustment. Nevertheless, the entire process is still quite sensible &ndash; the removal of a single image might lead to a completely different or wrong solution, or separation of image blocks. <br><br> In this paper we analyse the impact different parameters and strategies have on the solution. Those are a) the used tie point matcher, b) the used software for bundle adjustment. Using the data provided in the context of the ISPRS benchmark on multi-platform photogrammetry, we systematically address the mentioned influences. Concerning the tie-point matching we test the standard SIFT point extractor and descriptor, but also the SURF and ASIFT-approaches, the ORB technique, as well as (A)KAZE, which are based on a nonlinear scale space. In terms of pre-processing we analyse the Wallis-filter. Results show that in more challenging situations, in this case for data captured from different platforms at different days most approaches do not perform well. Wallis-filtering emerged to be most helpful especially for the SIFT approach. The commercial software pix4dmapper succeeds in overall bundle adjustment only for some configurations, and especially not for the entire image block provided.

scholarly journals INTEGRATION OF A GENERALISED BUILDING MODEL INTO THE POSE ESTIMATION OF UAS IMAGES

2016 ◽  
Vol XLI-B1 ◽  
pp. 1057-1064 ◽  
Author(s):  
J. Unger ◽  
F. Rottensteiner ◽  
C. Heipke
Keyword(s):  
Pose Estimation ◽  
Image Sequence ◽  
Image Sequences ◽  
Bundle Adjustment ◽  
Unmanned Aerial System ◽  
Real Image ◽  
Building Model ◽  
Current State ◽  
Image Orientation

A hybrid bundle adjustment is presented that allows for the integration of a generalised building model into the pose estimation of image sequences. These images are captured by an Unmanned Aerial System (UAS) equipped with a camera flying in between the buildings. The relation between the building model and the images is described by distances between the object coordinates of the tie points and building model planes. Relations are found by a simple 3D distance criterion and are modelled as fictitious observations in a Gauss-Markov adjustment. The coordinates of model vertices are part of the adjustment as directly observed unknowns which allows for changes in the model. Results of first experiments using a synthetic and a real image sequence demonstrate improvements of the image orientation in comparison to an adjustment without the building model, but also reveal limitations of the current state of the method.

scholarly journals Application of Wireless Sensor Networks to Prevent the Spread of Forest Fires

2021 ◽  
Vol 11 (11) ◽  
pp. 199-203
Author(s):  
Le Quang Bon ◽  
Keyword(s):  
Wireless Sensor Network ◽  
Sensor Network ◽  
Optical Sensors ◽  
Forest Fires ◽  
Digital Camera ◽  
Partial Solution ◽  
Optical Systems ◽  
Wireless Sensor ◽  
Network Systems ◽  
Camera Systems

The objective of this article is to identify current trends and prospects for the use of technical facilities and installations to prevent the spread of wildfires by analyzing the literature. The analysis of the literature has allowed an analysis of different ground-based wildfire detection and monitoring systems: optical sensors and digital camera systems, and wireless sensor network systems. The author concludes that the wireless sensor network can be seen as a partial solution when used in combination with other technologies. Keywords—observation towers, optical systems, optical sensors, digital cameras, wireless sensor network.

A Robust Feature Points Matching Algorithm in 3D Optical Measuring System

2011 ◽  
Vol 383-390 ◽  
pp. 5193-5199 ◽  
Author(s):  
Jian Ying Yuan ◽  
Xian Yong Liu ◽  
Zhi Qiang Qiu
Keyword(s):  
3D Reconstruction ◽  
Digital Camera ◽  
Image Data ◽  
Epipolar Geometry ◽  
Bundle Adjustment ◽  
Measuring System ◽  
Feature Points ◽  
3 Dimensional ◽  
Feature Points Matching ◽  
Optical Measuring

In optical measuring system with a handheld digital camera, image points matching is very important for 3-dimensional(3D) reconstruction. The traditional matching algorithms are usually based on epipolar geometry or multi-base lines. Mistaken matching points can not be eliminated by epipolar geometry and many matching points will be lost by multi-base lines. In this paper, a robust algorithm is presented to eliminate mistaken matching feature points in the process of 3D reconstruction from multiple images. The algorithm include three steps: (1) pre-matching the feature points using constraints of epipolar geometry and image topological structure firstly; (2) eliminating the mistaken matching points by the principle of triangulation in multi-images; (3) refining camera external parameters by bundle adjustment. After the external parameters of every image refined, repeat step (1) to step (3) until all the feature points been matched. Comparative experiments with real image data have shown that mistaken matching feature points can be effectively eliminated, and nearly no matching points have been lost, which have a better performance than traditonal matching algorithms do.

scholarly journals GNSS-Assisted Integrated Sensor Orientation with Sensor Pre-Calibration for Accurate Corridor Mapping

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2783 ◽  
Author(s):  
Yilin Zhou ◽  
Ewelina Rupnik ◽  
Paul-Henri Faure ◽  
Marc Pierrot-Deseilligny
Keyword(s):  
Satellite System ◽  
Sensor Calibration ◽  
Image Block ◽  
Integrated Sensor ◽  
Physical Constraints ◽  
Pose Determination ◽  
Sensor Orientation ◽  
Global Navigation Satellite ◽  
Oblique Images ◽  
The Impact

With the development of unmanned aerial vehicles (UAVs) and global navigation satellite system (GNSS), the accurate camera positions at exposure can be known and the GNSS-assisted bundle block adjustment (BBA) approach is possible for integrated sensor orientation (ISO). This study employed ISO approach for camera pose determination with the objective of investigating the impact of a good sensor pre-calibration on a poor acquisition geometry. Within the presented works, several flights were conducted on a dike by a small UAV embedded with a metric camera and a GNSS receiver. The multi-lever-arm estimation within the BBA procedure makes it possible to merge image blocks of different configurations such as nadir and oblique images without physical constraints on camera and GNSS antenna positions. The merged image block achieves a better accuracy and the sensor self-calibrated well. The issued sensor calibration is then applied to a less preferable acquisition configuration and the accuracy is significantly improved. For a corridor acquisition scene of about 600 m , a centimetric accuracy is reached with one GCP. With the provided sensor pre-calibration, an accuracy of 3.9 c m is achieved without any GCP.

Low Cost Digital Image Photogrammetry

1998 ◽  
Vol 14 (03) ◽  
pp. 202-213
Author(s):  
Clifford J. Mugnier
Keyword(s):  
Low Cost ◽  
Digital Camera ◽  
Dimensional Control ◽  
Charge Coupled Device ◽  
Imaging Arrays ◽  
Ccd Imaging ◽  
Camera Systems ◽  
Propagation Analysis ◽  
Error Propagation Analysis ◽  
3D Photogrammetry

A problem in modular shipbuilding is the lack of a reliable, low-cost method of obtaining and utilizing dimensional control in 3D. Photogrammetry has been successfully used as a tool for this application, but because of the large number of systematic errors associated with film-based cameras, only very large shipyards are using it. Recently, developments in Charge Coupled Device (CCD) imaging arrays for cameras have allowed some success in applying photogrammetric techniques dimensional control Mainstream photogrammetric software and hardware configurations have been expensive and complicated. Digital camera systems and computers were purchased and programmed to tie existing inexpensive software packages with Geometric Dilution of Control (GDOP) error propagation analysis, originally designed for topographic mapping, into a tool for production shipyard fabrication dimensional control.

scholarly journals Photo Scanner 3D Survey for Monitoring Historical Monuments. the Case History of Porta Praetoria in Aosta

2011 ◽  
Vol 6 ◽  
pp. 314-322 ◽  
Author(s):  
Paolo Salonia ◽  
Tommaso Leti Messina ◽  
Andrea Marcolongo ◽  
Lorenzo Appolonia
Keyword(s):  
Cultural Heritage ◽  
New Technology ◽  
Digital Camera ◽  
Point Clouds ◽  
3D Models ◽  
Stone Decay ◽  
Decay Kinetics ◽  
Image Block ◽  
Building Site ◽  
Historical Monuments

Accessibility to cultural heritage is one of the most important factors in cultural heritage preservation, as it assures knowledge, monitoring, Public Administration management and a wide interest on cultural heritage sites. Nowdays 3D surveys give the geometric basis for an effective artefact reconstruction but most of the times 3D data are not completely and deeply investigated to extract other useful information on historical monuments for their conservation and safeguard. The Cultural Heritage Superintendence of Aosta decided to run a time continual project of monitoring of the Praetorian Roman Gate with the collaboration of the ITABC, CNR of Italy. The Praetorian Roman Gate in Aosta, Italy, of Augustus ages, is one of the most well-known roman monumental gates, it is a double gate with three arches each side, 12 meters high, 20 meters wide, made of pudding stone ashlars, Badoglio, travertine, marble blocks and other stone insertion due to restorations between 1600 and 1950. In years 2000 a final restoration intervention brought the gate at the present state of art, within the frame of a restoration and conservation building site with the purpose of treat the different decay pathologies and conditions. A complete 3D geometric survey campaign has been the first step for the monitoring of the gate morphologic changes and decay progress in time. The main purpose is to collect both quantitative data, related to the geometry of the gate, and the qualitative data, related to the chromatic change on the surface due to the stone decay. The geometric data with colour information permits to associate materials and stone pathologies to chemical or mechanical actions and to understand and analyse superficial decay kinetics. The colours survey will also permit to directly locate on the 3D model areas of different stratigraphic units. The project aims to build a rigorous quantitative-qualitative database so to be uploaded into a GIS. The GIS will become the monitoring main means. Considering the huge dimension of the gate and its urban location a multi-scale approach has been considered. Controlled and free images have been taken from the ground and the top of the gate so to reconstruct all the walls and the upper cover. A topographic survey has been done so to be able to control and relate all the different acquisitions. It has been chosen a Photo Scanner 3D system. It is a photogrammetry-based survey technology for point clouds acquisition and 3D models configuration, from digital images processing. This technology allows to obtain point clouds (xyz coordinates) with RGB information and geometries at different levels of complexity by processing a number of images taken with a limited set of constraints, with the use of a simple acquisition equipment and through an image matching algorithm (ZScan, by Menci Software). Due to the high walls of the arch gates, the higher part has been surveyed with a remote controlled drone (UAV Unmanned Aerial Vehicle) with a digital camera on it, so to take pictures up to the maximum altitude and with different shooting angles ( 90 and 45 degree). This is a new technology which permits to survey inaccessible parts of a high monument with ease and accuracy, by collecting redundant pictures later bound together by an image block algorithm. This paper aims to present the survey experience architectural monuments trough the application of a trifocal quick photogrammetric system, in surveying at different scales and for different purposes.

Electron Holography and Digital Imaging for Analysis of Nanostructured Materials

1998 ◽  
Vol 4 (S2) ◽  
pp. 750-751
Author(s):  
L. F. Allard ◽  
E. Voelkl ◽  
A. K. Datye ◽  
A. H. Carim
Keyword(s):  
Nanostructured Materials ◽  
Digital Camera ◽  
Digital Processing ◽  
Quantitative Information ◽  
Electron Holography ◽  
Additional Information ◽  
Camera Systems ◽  
Phase Images ◽  
Ultra Fine Particle ◽  
Rapid Processing

Many nanostructured materials are formed from powder precursors having ultra-fine particle sizes. Techniques of electron microscopy have proven invaluable for characterizing the structure of the precursor materials in order to better understand the fundamental processes that govern consolidation of the materials into the final nanophase structures. In recent years, the rapidly developing technique of electron holography has increasingly been applied for characterizing particle morphologies. The advent of the modern field emission microscope, which offers beam coherency sufficient to produce high contrast interference fringes for optimum hologram formation, and especially the availability of digital camera systems for hologram acquisition and rapid processing have both combined to bring electron holography to the forefront of techniques for characterization of nanostructured materials.Electron holograms typically yield phase images that can give quantitative information on crystal morphologies, but much additional information can result from digital processing of holograms.

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