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Stability of zoom and fixed lenses used with digital SLR cameras
"... lens Consumer grade digital cameras are widely used for close range photogrammetric applications because of the convenience of digital images and the low cost of capture and reproduction. Since the introduction of digital cameras in the 1980s, there has been a strong divide between relatively inexpe ..."
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lens Consumer grade digital cameras are widely used for close range photogrammetric applications because of the convenience of digital images and the low cost of capture and reproduction. Since the introduction of digital cameras in the 1980s, there has been a strong divide between relatively inexpensive, low resolution, compact digital cameras, and relatively expensive, high resolution, professional digital cameras. In recent years, the improved affordability of SLR (Single Lens Reflex) style digital cameras has increased the use of this class of camera, to some degree displacing professional cameras. Digital cameras are quite often bundled with a consumer grade zoom lens that is designed for the quality of the image, rather than the geometric stability of the calibration. When these cameras are used for photogrammetric applications, it is common practice that a high quality, fixed focal length lens is purchased and used in preference to the zoom lens. Calibration tests were conducted on a range of different digital cameras, all within the SLR class, to ascertain the differences between zoom and fixed lenses when used with these cameras. Analyses are presented that indicate the differences between the two lens types in terms of accuracy, precision and stability and suggest that although acceptable results can be obtained using zoom lenses, a fixed lens provides superior results.
THE EFFECTS OF TEMPERATURE VARIATION ON SINGLE-LENS-REFLEX DIGITAL CAMERA CALIBRATION PARAMETERS
"... It is well known that temperature changes affect the geometric characteristics of cameras. Metric cameras, cameras specifically designed for photogrammetric work, are purposely built to maintain a stable geometry. However, the storage and working temperature variations can be very wide, whether the ..."
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It is well known that temperature changes affect the geometric characteristics of cameras. Metric cameras, cameras specifically designed for photogrammetric work, are purposely built to maintain a stable geometry. However, the storage and working temperature variations can be very wide, whether the cameras are used for airborne or terrestrial observations. Even with metric cameras self-calibration is often used when the highest quality of results are being pursued. The use of non-metric digital cameras particularly for terrestrial photogrammetric applications is not uncommon. The modern materials and the manufacturing quality of some digital cameras are now providing the photogrammetric community with great flexibility in lenses, camera bodies and functionality. With this the range of applications is expanding and for many organisations the ability to use a particular camera in this range of applications has made the investment in a digital camera more acceptable. In many climates where the weather conditions can vary greatly and the cameras can be put through a wide range of temperatures even between the storage and the location for use. For example, storage may be in a „warm ‟ office environment and the working location could be an indoor but „cold ‟ building or outdoor sub-zero work place. The question that must be asked is „what effect do these temperature changes have on the camera geometry? ‟ Sometimes the application allows sufficient image geometry for a selfcalibration, sometimes not. Should the cameras be allowed to „acclimatise‟? A number of questions can be raised related to variations in temperature. This paper will investigate and aim to quantify, the effect of variations in temperature on modern single-lens-reflex (SLR) digital
TARGETLESS CAMERA CALIBRATION
"... In photogrammetry a camera is considered calibrated if its interior orientation parameters are known. These encompass the principal distance, the principal point position and some Additional Parameters used to model possible systematic errors. The current state of the art for automated camera calibr ..."
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In photogrammetry a camera is considered calibrated if its interior orientation parameters are known. These encompass the principal distance, the principal point position and some Additional Parameters used to model possible systematic errors. The current state of the art for automated camera calibration relies on the use of coded targets to accurately determine the image correspondences. This paper presents a new methodology for the efficient and rigorous photogrammetric calibration of digital cameras which does not require any longer the use of targets. A set of images depicting a scene with a good texture are sufficient for the extraction of natural corresponding image points. These are automatically matched with feature-based approaches and robust estimation techniques. The successive photogrammetric bundle adjustment retrieves the unknown camera parameters and their theoretical accuracies. Examples, considerations and comparisons with real data and different case studies are illustrated to show the potentialities of the proposed methodology. a) b) Figure 1. A target-based calibration procedure (a) and the targetless approach (b). 1.
Contents lists available at ScienceDirect International Journal of Applied Earth Observation and
"... journal homepage: www.elsevier.com/locate/jag A community-based urban forest inventory using online mapping services and ..."
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journal homepage: www.elsevier.com/locate/jag A community-based urban forest inventory using online mapping services and
DIGITAL CAMERA CALIBRATION METHODS: CONSIDERATIONS AND COMPARISONS
"... Commission V, WG V/1 Camera calibration has always been an essential component of photogrammetric measurement, with self-calibration nowadays being an integral and routinely applied operation within photogrammetric triangulation, especially in high-accuracy close-range measurement. With the very rap ..."
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Commission V, WG V/1 Camera calibration has always been an essential component of photogrammetric measurement, with self-calibration nowadays being an integral and routinely applied operation within photogrammetric triangulation, especially in high-accuracy close-range measurement. With the very rapid growth in adoption of off-the-shelf digital cameras for a host of new 3D measurement applications, however, there are many situations where the geometry of the image network will not support robust recovery of camera parameters via on-the-job calibration. For this reason, stand-alone camera calibration has again emerged as an important issue in close-range photogrammetry, and it also remains a topic of research interest in computer vision. This paper overviews the current approaches adopted for camera calibration in close-range photogrammetry and computer vision, and discusses operational aspects for self-calibration. Also, the results of camera calibrations using different algorithms are summarized. Finally, the impact of chromatic aberration on modelled radial distortion is touched upon to highlight the fact that there are still issues of research interest in the photogrammetric calibration of consumer-grade digital cameras. 1.
AUTOMATIC RELATIVE ORIENTATION OF IMAGES 1
"... This paper presents a new approach to full automatic relative orientation of several digital images taken with a calibrated camera. This approach uses new algorithms for feature extraction and relative orientation developed in the last few years. There is no need for special markers in the scene nor ..."
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This paper presents a new approach to full automatic relative orientation of several digital images taken with a calibrated camera. This approach uses new algorithms for feature extraction and relative orientation developed in the last few years. There is no need for special markers in the scene nor for approximate values for the parameters of the exterior orientation. We use the point operator developed by D. G. Lowe (Lowe, 2004), which extracts points with scale- and rotation-invariant descriptors (SIFT-features). These descriptors allow a successful matching of image points even in situations with highly convergent images. The approach consists of the following steps: After extracting image points on all images each image pair is matched using the SIFT parameters only. No prior information about the pose of the images or the overlapping parts of the images is needed. For every image pair a relative orientation is computed using a RANSAC procedure. Here we use the new 5-point algorithm developed by D. Nister (Nister, 2004). Based on these orientations approximate values for the orientation parameters and the object coordinates are calculated. This is achieved by computing the relative scale and transforming into a common coordinate system. Several tests are carried out to ensure reliable inputs for the currently final step: a bundle block adjustment. The paper discusses the practical impacts of the algorithms involved. Examples of different indoor- and outdoor-scenes including a dataset of tilted aerial images are presented and the results of the approach are evaluated. These results show that the approach can be used for a wide range of scenes with different types of the image geometry and taken with different types of cameras including inexpensive consumer cameras. In particular we investigate in the robustness of the algorithms, e.g. in geometric tests on image triplets. In the outlook further developments like the use of image pyramids with a modified matching are discussed. 1.
STABILITY OF ZOOM AND FIXED LENSES USED WITH DIGITAL SLR CAMERAS
"... Consumer grade digital cameras are widely used for close range photogrammetric applications because of the convenience of digital images and the low cost of capture and reproduction. Since the introduction of digital cameras in the 1980s, there has been a strong divide between relatively inexpensive ..."
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Consumer grade digital cameras are widely used for close range photogrammetric applications because of the convenience of digital images and the low cost of capture and reproduction. Since the introduction of digital cameras in the 1980s, there has been a strong divide between relatively inexpensive, low resolution, compact digital cameras, and relatively expensive, high resolution, professional digital cameras. In recent years, the improved affordability of SLR (Single Lens Reflex) style digital cameras has increased the use of this class of camera, to some degree displacing professional cameras. Digital cameras are quite often bundled with a consumer grade zoom lens that is designed for the quality of the image, rather than the geometric stability of the calibration. When these cameras are used for photogrammetric applications, it is common practice that a high quality, fixed focal length lens is purchased and used in preference to the zoom lens. Calibration tests were conducted on a range of different digital cameras, all within the SLR class, to ascertain the differences between zoom and fixed lenses when used with these cameras. Analyses are presented that indicate the differences between the two lens types in terms of accuracy, precision and stability and suggest that although acceptable results can be obtained using zoom lenses, a fixed lens provides superior results. 1.
Article Geometric Stability and Lens Decentering in Compact Digital Cameras
, 2010
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Metric Potential of a 3D Measurement System Based on Digital Compact Cameras
, 2009
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Article Stability Analysis for a Multi-Camera Photogrammetric System Ayman Habib
, 2014
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