scholarly journals Perspective center determination

1969 ◽  
Author(s):  
J.D. McLaurin
Keyword(s):  
Perspective Center

Large scale particle image velocimetry measurement of river surface velocity based on images captured by a camera of the mobile phone

2020 ◽  
Author(s):  
Wen-Cheng Liu ◽  
Wei-Che Huang
Keyword(s):  
Particle Image Velocimetry ◽  
Mobile Phone ◽  
Large Scale ◽  
Particle Image ◽  
Digital Camera ◽  
Real Space ◽  
Surface Velocity ◽  
Image Velocimetry ◽  
Scale Particle ◽  
Perspective Center

<p>In this research, we conducted LSPIV (Large Scale Particle Image Velocimetry) measurements to measure river surface velocity based on images recorded by mobile phone. The realization of this research is based on the developments of two products. The first one is the digital camera, which has been combined with the mobile phone after several years of development. The second one is the three-axis accelerometer, which can measure the attitude of the object. A three-axis accelerometer is one of the necessary parts of the mobile phone nowadays, as many functions of the mobile phone, such as step counting, Do Not Disturb mode, games, require the detection of attitude.</p><p>In LSPIV, there are nine parameters of the collinear equation. Three of parameters are the coordinates of the perspective center in the image space (focus distance d and image center position (u, v)), which can be determined in advance in the laboratory; the other three parameters are the coordinates (x, y, z) of the perspective center in real space, which can be set to (0, 0, 0); the last three parameters are the attitude of the camera (i.e., the mobile phone), which is determined by the depression angle, the horizontal angle, and the left-right rotation angle and can be measured by three-axis accelerometer. Therefore, river surface velocity could be analyzed by LSPIV with not only continuous images captured by a camera of the mobile phone but also the acceleration values obtained by the three-axis accelerometer when each image was captured.</p><p>In the present study, Yufeng gauging station, which is in the upstream catchment of the Shihmen Reservoir in Taiwan, is selected as the study site. Two other measurement methods were used to measure the river surface velocity and the comparison was conducted. One is using a handheld digital flow meter and another is using LSPIV with control points to calculate the parameters for measuring the river surface velocity.</p>

Algorithm for determining the orientation elements of an infrared image obtained from a drone using reference points

2020 ◽  
Vol 958 (4) ◽  
pp. 41-50
Author(s):  
S.M. Mokrova ◽  
R.P. Petrov ◽  
V.N. Milich
Keyword(s):  
Focal Length ◽  
Three Dimensional ◽  
Infrared Image ◽  
Image Plane ◽  
Reference Points ◽  
Spatial Coordinates ◽  
Aerial Vehicle ◽  
True Position ◽  
Image Orientation ◽  
Perspective Center

The article deals with the algorithm for determining the exterior and interior orientation elements of an infrared image obtained from an unmanned aerial vehicle using four reference points. The idea of the proposed algorithm is to determine the true position of the image by the defined three-dimensional spatial coordinates of the reference points in the image at the time of shooting. The image plane is built up on the defined points. The coordinates of the principal point of the image are calculated by making a perpendicular from the perspective center to the plane of the image. The focal length is equal to the length of this perpendicular. Euler angles characterizing the position of the camera at the time of shooting are calculated after determining the axes’ directions of the inclined image coordinate system. The proposed algorithm is effective even in the case when all the elements of the image orientation are unknown. Calculations of the image elements on model examples with different initial data show high accuracy. The possibility of obtaining the necessary accuracy for the orthotransformation procedure was confirmed on real images.

scholarly journals Phase-stepped fringe projection by rotation about the camera’s perspective center

2011 ◽  
Vol 19 (19) ◽  
pp. 18458 ◽  
Author(s):  
Y. R. Huddart ◽  
J. D. Valera ◽  
N. J. Weston ◽  
T. C. Featherstone ◽  
A. J. Moore
Keyword(s):  
Fringe Projection ◽  
Perspective Center

Evaluation of Sopelem Presa 226RC Plotter for Independent Model Triangulation

1975 ◽  
Vol 29 (2) ◽  
pp. 209-224
Author(s):  
Francis H. Moffitt
Keyword(s):  
Flying Height ◽  
Wide Angle ◽  
Degree Polynomial ◽  
Vertical Control ◽  
Zero Position ◽  
Standard Deviations ◽  
Apparent Shift ◽  
The Stability ◽  
Perspective Center ◽  
Independent Model

The Presa 226RC is a first-order stereorestitution instrument accepting wide angle and super wide angle aerial photography. It is relatively unknown to photogrammetrists in North America. It was tested for the stability of its perspective centers, accuracy of plate measurements, and its suitability for independent model triangulation. Departure of perspective center coordinates from instrument zero position when moved through maximum rotational range amounts to 0.04 mm in x, 0.04 mm in y, and 0.02 mm in z. Base component displacements by" and bz’ needed in relative orientation cause an apparent shift of about 0.03 mm in all three directions. Standard deviations of plate coordinates of 20 grid intersections used in perspective center stability tests are: σx′ = ±0.007 mm, σy′ = ±0.007 mm, σx″ = ±0.006 mm, and σy″ = ±0.004 mm. Independent model triangulation of four separate short strips of a heavily controlled area was adjusted by Schut’s 2nd degree polynomial adjustment. Standard deviations at plate scale are σx = ± 0.012 mm; σy = ± 0.012 mm. The relative accuracy of vertical control points is about 1/8,000 of the flying height.

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