KEYWORDS: Spherical lenses, Stereoscopy, Visualization, 3D modeling, Panoramic photography, 3D acquisition, 3D image processing, Projection systems, Clouds, 3D displays
Spherical images are linear images, which are exact in central projection. They are explicitly determined by the projection centre. The technical approach consists of collecting scenery through a single perspective and combining the images like panoramic mosaics.
A general application of spherical imaging is hempispehric visualisation of space. In hemispheric visualisation, we distinguish between horizontal, half hemispheric, and full hemispheric imaging. The photogrammetric applications of spherical imaging aim at acquisition of 3D environmental or terrain models. Then the base to distance ratio is typically large.
We assume, that the primary advantage of spherical imaging will be nevertheless on stereoscopy applications. We aim at full-scale stereoscopy with projection of spherical images in scale of 1:1. In case of full-scale stereoscopy, the stereoscopic plasticity will have a value of 1 and the base is typically short. Natural viewing would equal to base lengths of human eyes, i.e. to 65 mm.
We present in the paper the Stereodrome, which is a physical realisation of full-scale stereo viewing. It consists of a photogrammetric workstation, a high-resolution stereo projector, necessary stereo eye-ware, and a back projection screen. Originally we have motivated us for building the Stereodrome by the fact that it is the only means to really see the behaviour of 3D point clouds in details. In the paper we will also discuss, in which way full-scale stereo display has been used for validating the quality of existing 3D geoinformation.
This paper evaluates and discuses the accuracy of laser scanner in DTM (digital terrain model) generation in forested and suburban areas. Special emphasis is laid in order to optimize the selection of ground hits used for the creation of the DTM of future high-pulse-rate laser scanners. A novel DTM algorithm is depicted in detail. The algorithm is based on five phases: (1) calculation of the original reference surface, (2) classification of vegetation and removal of the vegetation from the reference surface, (3) classification of the original cloud of points using the reference surface, (4) calculation of the DTM based on the classified ground hits, and (5) interpolation of the missing points. Standard error of 15 cm was obtained for flat forest areas and the error increased with increasing terrain slope to the value of approximately 40 cm at the slope of 40%. The average standard error for forest area was slightly better than 25 cm. The laser-derived DTM of the forest road deviated only 8.5 cm from the true height. An optimum performance for the DTM generation was obtained by averaging the ground hits which located, at the maximum, 60 cm above the minimum terrain values. A simplified algorithm was suggested for more operational use based on the first pulse mode data. Special cases of the suburban area DTM were verified including terrain heights below the buildings and bridges, terrain heights of roads, terrain heights below large outdoor light fixture, to name but a few. About 100 special cases in suburban/urban environment for DTM verification were searched. The corresponding standard error between the laser-derived values and reference data was 45 cm.
The paper deals with concentric image capturing and its use for mapping and visualization purposes. The work is based on a photogrammetric approach in composing hemispheric images from concentric image sequences.
The paper deals with our research on developing videogrammetry based 3D modeling procedure for indoor facilities. The modeling is based on recorded video sequences, and the analysis procedure is reverse if compared to the traditional one. Here a functional 3D model is built first and the measurements for exact geometry are done thereafter: `Modeling first--then measuring'. The final output will be a photorealistic model.
Measurements of dimensions of inaccessible objects remains a challenge in spite of new technologies available. The authors of this article approach the problem with a photogrammetric method using a laser-camera combination installed in a helicopter. The method was applied to the topographic measurement of ice fields.
The application of video imagery for photogrammetric tasks may be divided according to the task into on-line or off-line use. In Finland, the first successful on-line systems were installed for the position measuring of car bodies in Spring 1992. The on-line applications have grown interest within industrial production because they are operative and a payback period is thus countable. As it regards the off-line use, the situation is different and the efficiency in 3D data acquisition seems to play the decisive role. In the paper the different characteristics in performing the on-line and off-line videogrammetry are presented. The 3D measurements are exemplified with the applications. These cover both existing references in industrial `on-line' applications and ongoing development of `off-line' 3D object digitizing procedures.
We discuss an off-line 3D measuring procedure under development in a project for the national program on machine vision in Finland 1992-1996. The procedure consists of four concurrent phases: (1) recording, (2) rectification, (3) digitizing, and (4) modeling. The recordings are based on sequential stereo videography, and the continuous object digitizing is based on the rigid normal case of stereography. The system modules are as follows: (1) two video cameras, (2) controllable feature projector, and (3) photogrammetric station. The procedure is interactively linked to a CAD/CAM-environment both for reverse engineering and quality control use.
KEYWORDS: Calibration, Cameras, Robotics, 3D acquisition, Image processing, Control systems, Machine vision, Computer vision technology, Visual process modeling, Video
A photogrammetric station is a configuration of several video cameras which are used for automated 3D measuring of industrial objects. All measurements are performed from the image observations only, and the targets are natural features or projected light patterns. The first `on-line' applications are for car body orientation within a robotic sealing cell and for 3D verification of ship screws within a robotic machining step. The `off-line' applications are for object reconstructions for reverse engineering purposes.
KEYWORDS: 3D vision, Robots, Cameras, Calibration, 3D image processing, Control systems, Image processing, 3D acquisition, Manufacturing, Process control
Automated photogrammetric vision systems, called photogrammetric stations, are used for industrial on-line control. The stations are on-site calibrated camera setups with necessary image processing in order to provide the manufacturing process with three-dimensional control data. One of the first operative industrial applications is the car body orientation within a seam sealing cell in automotive manufacturing.
KEYWORDS: 3D image processing, Robot vision, 3D vision, Image processing, 3D acquisition, Process control, Sensors, Solid state cameras, Calibration, Space robots
Photogrammetric stations are used for vision based dynamic control of 3-D related phenomena. The vision sensors are fixed solid-state cameras which are permanently mounted and set up for a specific control task. The on-site calibration of the station allows the continuous processing of the 3-D space coordinates for all object points according to their actual 2-D image locations For automated control processes the object points are targeted using predefined templates extracted from the perspective images. The precision of an object point measured by the station is better than 1:10,000 of the object volume in all three coordinates. The vision application presented here is the locating of car bodies in the 3-D space of a robotic sealing cell.
Some principles of using template images for close-range photogram- metric coordinate determination are described. The primary use is the automatic stability control of the photogrammetric stations. In the case of applications, such as within manufacturing process cont- rol, the template images substitute the need of manual targetting.
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