Showing papers on "Photogrammetry published in 1997"

Practical use of video imagery in nearshore oceanographic field studies

Abstract: An approach was developed for using video imagery to quantify, in terms of both spatial and temporal dimensions, a number of naturally occurring (nearshore) physical processes. The complete method is presented, including the derivation of the geometrical relationships relating image and ground coordinates, principles to be considered when working with video imagery and the two-step strategy for calibration of the camera model. The techniques are founded on the principles of photogrammetry, account for difficulties inherent in the use of video signals, and have been adapted to allow for flexibility of use in field studies. Examples from field experiments indicate that this approach is both accurate and applicable under the conditions typically experienced when sampling in coastal regions. Several applications of the camera model are discussed, including the measurement of nearshore fluid processes, sand bar length scales, foreshore topography, and drifter motions. Although we have applied this method to the measurement of nearshore processes and morphologic features, these same techniques are transferable to studies in other geophysical settings.

Automation of interior, relative, and absolute orientation

Abstract: Considerable progress has been achieved in the automation of image orientation for photogrammetry and remote sensing over the last few years. Today, autonomous software modules for interior and relative orientation are commercially available in digital photogrammetric workstations (DPWS), and so is automatic aerial triangulation. The absolute orientation has been successfully automated for a number of applications. In this paper recent developments and the state of the art in automatic image orientation are presented.

Quantitative photogrammetric analysis of digital underwater video imagery

Abstract: This paper presents a photogrammetric model for digital underwater video imagery, which has been mostly applied to qualitative analysis in the marine environment. With this model, quantitative analysis of underwater images is possible, e.g., to locate positions, calculate sizes, and measure shapes of objects from image features. The underwater photogrammetric model is based on a three-dimensional optical ray tracing technique which rigorously models imaging systems with multilens configurations and multiple refractions. The calibration procedure with two independent phases has been proven to be efficient in simplifying the computation and improving the calibration accuracy. With the current imaging system configuration and photogrammetric model, an accuracy of 0.8 cm in lateral directions and 1.2 cm along the depth direction for objects located about 2-3 m from the camera system in the object space is attainable. A PC-based digital underwater photogrammetric prototype system has been developed to implement the underwater photogrammetric model.

Portable measurement system using image and point measurement devices

Abstract: Calibrated spatial reference devices (SRDs) of known dimensions having targets at known relative locations are attached to a large structure to be measured. A design device employs a digital camera to acquire digital images of `islands` of the structure including the SRDs and employs photogrammetry techniques to determine relative locations of `islands` within a large structure. A highly accurate coordinate measurement device provides absolute 3D measured locations of the targets used to convert the relative photogrammetry locations into absolute 3D locations. A monitor displays the digital images, measured 3D locations, photogrammetry locations in a superimposed manner to a user and a user interface allows the user to select objects to be measured. Image detection techniques are used to identify objects selected by a user and dimensions, and distances between selected objects are automatically calculated. A remote link allows remote users to interact with the device to view, select structures and measure dimensions. The device is also capable of storing any type of imagery, notes, voice annotations, and also capable of retrieving archived information. This allows a time-lapse playback of objects indicating wear or corrosion.

Use of terrestrial photogrammetry for monitoring and measuring bank erosion

Abstract: This paper examines the use of terrestrial photogrammetry as a technique for measuring bank erosion in a rapidly changing fluvial environment. It has been recognized that there are a number of advantages when applying photogrammetric techniques to geomorphological situations. In this study the enhancement of spatial sampling combined with the ability to capture additional information, such as soil moisture, on film, is of particular importance in enabling the identification of specific processes involved in bank erosion as well as detailed volumetric analysis of losses. Metric terrestrial photography was taken of the river bank on several dates, and data were abstracted by the use of analytical photogrammetry. This enabled the generation of digital terrain models from which morphological and volumetric changes could be assessed.

Automated DEM extraction and orthoimage generation from SPOT Level 1B imagery

Abstract: This paper describes the testing and validation of the photogrammetric modules of the PC1 EASI/PACE system using SPOT stereo-pairs over a high accuracy test field established in a desert area in Jordan. The mathematical modeling and analytical photogrammetric solution used by the system are first described. This is followed by a description of the algorithm employed in the automatic image matching procedure used to extract a dense DEM from the SPOT digital image data. The results of extensive tests of the geometric accuracy of the exterior orientation and analytical rectification carried out with the SPOT images using EASUPACE are given. The DEMs generated from five SPOT Level 1B stereo-pairs have been merged and validated through a comparison of the resulting contours with the corresponding contours generated by aerial photogrammetric methods, the two plots showing an excellent agreement. The final ortho-images are of a high quality in radiometric terms, while a check of their geometric accuracy reveals sub-pixel accuracy. The results of this highly automated all-digital photogrammetric procedure are of considerable relevance to those concerned with the topographic mapping of extensive areas of arid and semi-arid terrain.

Evaluating the potential of the forthcoming commercial US high-resolution satelite sensor imagery at the Ordnance Survey

Abstract: As the National Mapping Agency of Great Britain, the Ordnance Survey" (0s) is driven by a need to reduce costs and commercialize operations, and as such has been investigating photogrammetric methods to improve existing products, streamline existing production, and increase the current portfolio of products. Over the last 18 months, the 0s has been involved in a major research project to tackle these issues through an evaluation of the forthcoming commercial U.S. high spatial resolution satellite sensors which are offering 1-m panchromatic and 4-m multispectral spatial resolutions. Work has focused on improving the existing National Height Dataset (NHD), reducing the cost of photogrammetric survey, automatic topographic feature change detection, production of DM; three-dimensional (30) urban models, and land-use classification. Results from the project using simulated imagery indicate that it would have potential within the 0s in all areas evaluated. The work now needs to be followed up when real high spatial resolution satellite imagery becomes commercially available.

A New Approach to Precision Airborne GPS Positioning for Photogrammetry

Abstract: Precise determination of GPS phase ambiguity integers on the fly is a key requirement for accurate kinematic positioning. A fully automatic approach is developed to resolve phase integers and perform airborne GPS positioning for aerial triangulation using dual-frequency GPS data. Although always helpful, static initialization is not required; the problem of signal interruptions (losses of lock) while an airplane is maneuvering distant from a base station has also been addressed. Test results show that positions using precise phase data are reliably determined with this approach.

Investigation of the Kodak DCS460 digital camera for small-area mapping

Abstract: Small-format aerial photography is seen as a low-cost alternative to large-format photography for local area mapping. As CCD sensor resolutions and format sizes improve, digital sensors are becoming viable alternatives to small-format analogue cameras. This article reports on investigations into the use of the Kodak DCS460 digital camera for mapping the Marconi Beam informal settlement in Cape Town. Issues involving the practical use of the camera including calibration, photogrammetric limitations, image interpretation and measurement are discussed. Stereopairs of DCS460 images at 1 : 18,500 scale yielded accuracies in the order of ±0.2 m in planimetry and ±0.6 m in elevation. While these accuracies are sufficient for many mapping exercises the limited format size of the camera and slow image download times economically restrict application of the camera to the mapping of small areas.

Photogrammetry as a research tool for glaciology

Abstract: Using a multidisciplinary project studying surging glaciers in Svalbard as a reference, this paper examines some of the ways in which photogrammetry can be used as a research tool by glaciologists. Photogrammetric compilations of two of the glaciers under study were produced from 1990 aerial photography. Photogrammetry was regarded primarily as a source of digital elevation models in this project, rather than as a cartographic tool. Problems encountered in applying photogrammetry to the arctic terrain are considered and a methodology devised to ameliorate these problems by maximizing the available data is described. The results of the photogrammetric work are presented and difficulties in quantifying the accuracy of the photogrammetric data are examined. Examples of the ways in which the photogrammetrically derived digital data have been used for glaciological analysis and visualization are discussed.

Self-calibrating shape-measuring system based on fringe projection

Abstract: The goal of optical 3D-measurements is the determination of Cartesian coordinates of surfaces. Using principles basing on fringe projection techniques coordinates are calculated of measured phases in fringes, image-coordinates of cameras and parameters of the system configuration. Mostly, three measured values unambiguous lead to one coordinate-tripel. A more comfortable way offers photogrammetric measurements where more than three values are measured to calculate coordinates and additional to parameters describing the system configuration. Applying these experiences to fringe projection techniques it is possible to combine the advantages of both techniques. That guarantees high number of object points, quick data acquirement and a simultaneous determination of coordinates and system parameters with photogrammetric bundle adjustment. Recent measurements show the capabilities of that principle. The reliability of the coordinates is given by a standard deviation of less than 10 microns while the object diameter was up to 280 mm.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Digital rectification and generation of orthoimages in architectural photogrammetry

Abstract: This paper gives an overview over different photogrammetric single image techniques, like digital rectification, unwrapping of parametric surfaces and differential rectification methods. It shows the new possibilities for the generation of orthoimages and image mosaics using digital image processing methods even on low-cost personal computers. After a short description of the implemented methods, there are presented some results in the field of architectural photogrammetry and monument preservation.

Dynamic photogrammetric calibration of industrial robots

Abstract: Today’s developments in industrial robots focus on aims like gain of flexibility, improvement of the interaction between robots and reduction of down-times. A very important method to achieve these goals are off-line programming techniques. In contrast to conventional teach-in robot programming techniques, where sequences of actions are defined step-by-step via remote control on the real object, off-line programming techniques design complete robot (inter-)action programs in a CAD/CAM environment. This poses high requirements to the geometric accuracy of a robot. While the repeatability of robot poses in the teach-in mode is often better than 0.1mm, the absolute pose accuracy potential of industrial robots is usually much worse due to tolerances, eccentricities, elasticities, play, wear-out, load, temperature and insufficient knowledge of model parameters for the transformation from poses into robot axis angles. This fact necessitates robot calibration techniques, including the formulation of a robot model describing kinematics and dynamics of the robot, and a measurement technique to provide reference data. Digital photogrammetry as an accurate, economic technique with realtime potential offers itself for this purpose. The paper analyzes the requirements posed to a measurement technique by industrial robot calibration tasks. After an overview on measurement techniques used for robot calibration purposes in the past, a photogrammetric robot calibration system based on off-the-shelf lowcost hardware components will be shown and results of pilot studies will be discussed. Besides aspects of accuracy, reliability and self-calibration in a fully automatic dynamic photogrammetric system, realtime capabilities are discussed. In the pilot studies, standard deviations of 0.05-0.25mm in the three coordinate directions could be achieved over a robot work range of 1.7 x 1.5 x 1.0 m 3 . The realtime capabilities of the technique allow to go beyond kinematic robot calibration and perform dynamic robot calibration as well as photogrammetric on-line control of a robot in action.

A procedure for automatic absolute orientation using aerial photographs and a map

Abstract: This paper describes a method of determining common points in a photogrammetric model and on a map for the purpose of absolute orientation. This procedure forms part of an automated system for exterior orientation which first involves automatic relative orientation. The method is based on the identification of common polygons within the image and the map, the exact matching of the polygon boundaries, malting allowance for changes and differences in the boundary between image and map, and finally the determination of three-dimensional co-ordinates in the model and on the ground with which to determine the transformation. The method is based on a number of algorithms described elsewhere, particularly the use of chain code and dynamic programming. The possible errors in the system are investigated and a practical test is described. It is concluded that the method has potential for use where existing maps are available and where sufficient detail is present on the image and on the map to ensure a large number of well distributed points which can be used for orientation.

Aerotriangulation and DEM/Orthophoto Generation from High-Resolution Still-Video Imagery On the Potential of Digital Cameras Onboard an Aircraft

Abstract: High-resolution solid-state sensor matrix cameras have found quite some interest among photogrammetrists in the last few years. The limited resolution of such cameras has so far restricted their practical use to applications in digital closerange photogrammetry. Nevertheless, the advantages of the direct acquisition and processing of digital image data in combination with the accuracy potential and the increasing resolution of solid-state sensors have started to make digital cameras interesting for a number of applications in aerial photogrammetry. This paper presents two practical studies on the helicopter-based use of a high-resolution digital still-video camera for digital aerotriangulation and the automatic generation of digital elevation models and orthophotos. Test regions were an alpine village and a landslide area in Switzerland. The current performance and future developments of solid-state matrix sensors are shown, and the advantages and disadvantages of the use of digital cameras in aerial applications are discussed. Using self-calibration techniques, externally verified accuracies of 2 cm for planimetry coordinates and 5 to 6 cm for height coordinates were obtained in digital aerotriangulation using imagery of 1 :20,000 scale, and a precision of 0.03 percent of the flying height above ground could be achieved for digital elevation models.

3D-metrologies for industrial applications

Abstract: Three-dimensional-metrology based on photogrammetric and topometric techniques is a powerful tool for the digitization and measurement of complex three-dimensional scenes and objects. Since several years advanced sensors and measurement systems are available for industrial applications. Especially the integration of topometric systems into measuring- and handling machines is supported by compact and light 3D- sensors. These sensors can be optimized for specific measuring tasks with respect to accuracy, field of view and further parameters. During the last two years one is going to describe both techniques by the same algorithms. Moreover, there are first approaches of 'topogrammetric' systems, that combine photogrammetric and topometric metrologies, especially by using calibration techniques that are well known in photogrammetry and which allow the on-line calibration of 3D- sensors. On the other hand the topometric projection of coded light provides a continuous indexing of the whole measuring scene where photogrammetric methods (without active illumination) are limited to a lower number of discrete index marks.

An evaluation of fuzzy approaches to mapping land cover from aerial photographs

Abstract: Fuzzy approaches are of increasing importance for representing and handling geographical area and boundary delineations. This paper evaluates three different approaches that may be applied to derive fuzzy maps of land cover obtained by photogrammetry from aerial photographs. The three approaches are all spatial interpolation methods, based respectively on distances, on triangulated irregular network (TIN) models and on indicator kriging. For each approach, a set of methods for assessing the accuracies of fuzzy maps has been employed, including the overall classification accuracy, entropy, cross-entropy and divergence. A local Edinburgh suburb was used as a test site where there is a mixture of well-defined and poorly defined locations. It was found that while the TIN model-based approach produces the best empirical results in terms of the overall classification accuracy, entropy and cross-entropy, indicator kriging is theoretically the most sound approach to deriving fuzzy maps of land cover from photogrammetric data, especially when fuzziness is properly accommodated in the assumed reference data.

Exploitation of Linear Features in Surveying and Photogrammetry

Abstract: Modeling of linear features, particularly straight lines and circles, in two-dimensional (2D) and three-dimensional (3D) spaces, is developed, with specific consideration of independent descriptors. This is followed by the derivation of the four-, six-, and eight-parameter 2D transformations in terms of the line and circle parameters, as well as 3D linear transformation. Minimum configuration, redundant cases, and restrictions regarding special cases are carefully noted and are compared to the cases of using points only. Many useful geometric constraints between linear features, which provide significant information, are identified and corresponding equations are developed. Constraints involving relative geometric information relating features to each other are considered in addition to those constraints relating features to the reference coordinate system. Finally, the standard point-based photogrammetric collinearity equations are replaced by those based on correspondence between image and object linear features. Results are presented describing experiments where the coordinates of points are perturbed using Gaussian random noise to emulate real data. Several thoughts are listed regarding the future applications of this research in practice.

Monitoring glacier changes using a global positioning system in differential mode

Abstract: Recent developments of global positioning systems (GPS) have provided opportunities for rapid and frequent glacier mapping. The speed and accuracy of GPS techniques make them particularly suitable for repeated glacier mapping. Using two receivers in differential mode provides very high accuracy. In July 1995, a kinematic differential GPS survey of Austre Okstindbreen, one of the glaciers in the Norwegian national programme of mass-balance studies, provided three-dimensional positions of 2228 points in less than 6.5 h. Handling the data in a geographic information system permitted construction of a triangular irregular network digital terrain model (TIN DTM), which could be compared with TIN DTMs constructed from 1981 and 1993 surveys based on aerial photogrammetry and electronic distance measurement, respectively. A TIN DTM has advantages over the more usual grid-based DTM, which incorporates many interpolated values, although interpolation also is necessary if contours are to be derived from a TIN model. The aspect and gradient of triangular facets in the 1995 DTM have been used to produce a map which has considerable potential for detailed energy-balance studies of the glacier’s accumulation area.

High-speed correspondence for object recognition and tracking

Abstract: Real-time measurement using multi-camera 3D measuring system requires three major components to operate at high speed: image data processing; correspondence; and least squares estimation. This paper is based upon a system developed at City University which uses high speed solutions for the first and last elements, and describes recent work to provide a high speed solution to the correspondence problem. Correspondence has traditionally been solved in photogrammetry by using human stereo fusion of two views of an object providing an immediate solution. Computer vision researchers and photogrammetrists have applied image processing techniques and computers to the same configuration and have developed numerous matching algorithms with considerable success. Where research is still required, and the published work is not so plentiful, is in the area of multi-camera correspondence. The most commonly used methods utilize the epipolar geometry to establish the correspondences. While this method is adequate for some simple situations, extensions to more than just a few cameras are required which are reliable and efficient. In this paper the early stages of research into reliable and efficient multi-camera correspondence method for high speed measurement tasks are reported.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Accuracy potential of large-format still-video cameras

Abstract: High resolution digital stillvideo cameras have found wide interest in digital close range photogrammetry in the last five years. They can be considered fully autonomous digital image acquisition systems without the requirement of permanent connection to an external power supply and a host computer for camera control and data storage, thus allowing for convenient data acquisition in many applications of digital photogrammetry. The accuracy potential of stillvideo cameras has been extensively discussed. While large format CCD sensors themselves can be considered very accurate measurement devices, lenses, camera bodies and sensor mounts of stillvideo cameras are not compression techniques in image storage, which may also affect the accuracy potential. This presentation shows recent experiences from accuracy tests with a number of large format stillvideo cameras, including a modified Kodak DCS200, a Kodak DCS460, a Nikon E2 and a Polaroid PDC-2000. The tests of the cameras include absolute and relative measurements and were performed using strong photogrammetric networks and good external reference. The results of the tests indicate that very high accuracies can be achieved with large blocks of stillvideo imagery especially in deformation measurements. In absolute measurements, however, the accuracy potential of the large format CCD sensors is partly ruined by a lack of stability of the cameras.

Digital underwater photogrammetric system for large scale underwater spatial information acquisition

Abstract: An UNderwater Digital Photogrammetric System (UNDIPS) has been developed jointly by The University of Calgary and Canadian Hydrographic Services (CHS). An underwater photogrammetric model considering the lens distortion, housing cover corrections, and the medium refraction has been developed. It corrects the displacements of image points caused by the distortion and refraction so that the photogrammetric processing can be treated as a reduced central perspective transformation and modified direct linear transformation (DLT) can be applied. The calibration of the system is performed in two phases. This allows the examination of characteristics of the system associated with the cameras, the housing covers, and the medium refractions separately. With the current configuration, the achievable accuracy of object points which are 2–2.5 m from the cameras in the object space is 0.3 cm in the x and y directions and 1.0 cm in the z direction (depth).

One step to a higher level of automation for softcopy photogrammetry automatic interior orientation

Abstract: The efforts and status of fully automatic interior orientation (AIO) for digital photogrammetric systems are presented in this paper. A fully automatic AIO module, based on template matching, together with least squares matching (LSM) techniques suitable for most commercially available aerial cameras, has been installed on SoftPlotter™ softcopy photogrammetric workstations from Vision International for over two years. A success rate of one hundred percent for fiducial recognition with very high position accuracy was achieved on several hundred test frames. Thousands of frames have been processed with AIO by SoftPlotter™ users with satisfactory results. The processing time averages a few seconds per frame with eight fiducials.

Applications and Tools

Abstract: From the beginning of science, visual observation has played a major role. At that time, the only way to document the results of an experiment was by verbal description and manual drawings. The next major step was the invention of photography which enabled results to be documented objectively. Three prominent examples of scientific applications of photography are astronomy, photogrammetry, and particle physics. Astronomers were able to measure positions and magnitudes of stars and photogrammeters produced topographic maps from aerial images. Searching through countless images from hydrogen bubble chambers led to the discovery of many elementary particles in physics. These manual evaluation procedures, however, were time consuming. Some semi- or even fully automated optomechanical devices were designed. However, they were adapted to a single specific purpose. This is why quantitative evaluation of images did not find widespread application at that time. Generally, images were only used for documentation, qualitative description, and illustration of the phenomena observed.

Hemispherical Photographs Used for Mapping Confined Spaces

Abstract: This paper presents two methods for using fisheye photographs for mapping confined areas. The first approach is intended for relatively flat objects, observed at very close range, and consists of producing a rectified view from a fisheye photograph. After scanning and correcting the spherical distortions present in the original image, a simple projective transformation creates a constant scale image from which two-dimensional (2D) data can be extracted. The second method aims at recovering three-dimensional data from two stereo fisheye photographs. This method also involves the same image correction for spherical distortions, but the two resulting perspective images are afterwards analyzed utilizing stereovision in a digital photogrammetric workstation. Practical experiments, conducted with a 35-mm camera equipped with a fisheye lens, demonstrate the applicability and feasibility of the two softcopy photogrammetry methods in the context of mapping electric distribution wells.

Target for photogrammetry

Abstract: PROBLEM TO BE SOLVED: To obtain a target for photogrammetry which is simply placed and easily moved, by providing a constitution having a predetermined number of reference points arranged with a constant distance between any two of them and located on the same plane. SOLUTION: A target 10 comprises at least three reference points. In the case of for example, an equilateral triangular plate 12 of thickness 2-3 mm, a side of the equilateral triangle is approximately 1 m in length. The vertexes 14, 16, and 18 of the triangular plate 12 form the reference points P1 , P2 and P3 , and the plane of the triangular plate 12 forms a reference plane. The triangular plate 12 is formed of an acrylic resin, and marking is performed as necessary so that the reference points i.e., the vertexes 14, 16, and 18 may be easily distinguished. In addition. the shape, size, and material of the target 10 is not especially limited. As at least three reference points are arranged at predetermined known intervals at all times by using the target 10, the labor of measuring a reference length for every photogrammetry with a measuring tape, etc., is saved. In addition, as a reference plane is determined by the three reference points on the target at all times, it is easy to process picked-up image data by a computer, and further it is possible to recognize the image points of the reference points in a picked-up image easily.

The necessity of exterior orientation parameters for the rigorous geometric correction of MEIS‐II airborne digital images

Abstract: Remote sensing is an essential element of the Canada Land Use Monitoring Program. The program sought the replacement, before 1991, of classical aerial photographs by remote sensing imagery (satellite or airborne) as the main source of data for land management (Wilson, 1986). In this sense, the Canada Centre for Remote Sensing (CCRS) has been involved over the last few years in a project for implementing an airborne multi‐detector electro‐optical imaging system (MEIS‐II). The acceptance of airborne scanners has been slow over the years principally because of poor spatial resolution and distortions induced by aircraft motion. For addressing this geometric problem, CCRS has developed a rigorous correction method based on a fundamental photogrammetric principle (colinearity condition) and auxiliary navigation data (attitude, altitude and aircraft speed) measured in relation to time by an inertial navigation system (INS). The method can process images in monoscopy or stereoscopy (two flight lines or more, in w...