Truncated Epipolar Line Matching Method Based on Image Rectification

2014 ◽

Vol XL-4 ◽

pp. 87-91

Author(s):

J.-S. Hsia

Keyword(s):

Image Matching ◽

Particle Swarm ◽

Window Size ◽

Pso Algorithm ◽

Least Square ◽

Image Point ◽

Reference Image ◽

Epipolar Line ◽

Matching Method ◽

The Difference

This paper presents a method for determining the 3D position of an image point on a reference image using particle swarm optimization (PSO) to search the height (Z value) that gives the biggest Normalized Cross Correlation (NCC) coefficient. The searching area is in the surrounding of the height of the image point. The NCC coefficient evaluates the similarity with the image point and a corresponding point on an epipolar line in the search image. The position of corresponding image point on the epipolar line is determined by the height point on a sloping line locus. The PSO algorithm starts with a swarm of random particles. The position of each particle is a potential solution in the problem space. Each particle is given a randomized velocity and attracted toward the location of the best fitness. The position of each particle is iteratively modified by adding a newly computed velocity to its current position. The velocity is updated by three factors which are two attractions from local best position and global best position, two strengths of the attractions, and two uniform random numbers for each attraction. The iteration will stop when the current solution is convergent. The time of computation is highly related to the range of height and the interval of height enumeration when the approach to find a corresponding image point of an image point on a reference image is based on the height enumeration along sloping line locus. The precision of results can be improved by decreasing the interval of height enumeration. This shows the limitation of the enumeration method in the efficiency and accuracy. The issue is overcome by a method of using PSO algorithm. The proposed method using different parameters such as the size of image window, the number of particles, and the size of the height searching range has been applied to aerial stereo images. The accuracy of tested results is evaluated on the base of the comparison to the reference data from the results of least-square matching being manually given initial points. The evaluation result shows that tested results has given a solution to a level of less than 1 centimetre without using refined image matching method. The same level of accuracy can reach even when the searching range is bigger than 90 meters. But the difference of image window size may lead to the change of the matching result. And, without the procedures of both coarse-to-fine hierarchical solution and refined image matching method, the algorithm still can give the same accuracy level of least-square image matching resulting. This method also shows its ability to give reasonable matching results without manual assistance.

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Stereo Image Matching Based on SURF Descriptor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1083.142 ◽

2015 ◽

Vol 1083 ◽

pp. 142-147

Author(s):

Luan Zeng ◽

You Zhai

Keyword(s):

Image Matching ◽

Euclidean Distance ◽

Small Neighborhood ◽

Stereo Image ◽

Epipolar Line ◽

Matching Method ◽

Matching Efficiency ◽

Stereo Image Matching ◽

Calibration Parameters ◽

Better Than

In order to improve the robustness performance of SURF descriptor applied to stereo image matching, a new matching method is proposed. By using the ratio of minimum to second min Euclidean distance of corresponding features, we can get the coarse matching points aggregation. Then, the epipolar line is computed from calibration parameters. Correspondences are taken as correct correspondences, only if they fall into a small neighborhood of their epipolar line. Taken errors into account, the neighborhood is set (-3, 3). Using this restriction, we can get the correct matching points aggregation. The experimental results show that the correct matches and matching efficiency are better than RANSAC.

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Three-Steps Uncalibrated Rectification Using Epipolar Distance Transform

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.411-414.1341 ◽

2013 ◽

Vol 411-414 ◽

pp. 1341-1347

Author(s):

Li Mei Fu ◽

Guo Hua Peng

Keyword(s):

Efficient Method ◽

Estimation Error ◽

Distance Transform ◽

Relative Rotation ◽

Epipolar Line ◽

Image Rectification ◽

Visual Effect ◽

Image Intensity ◽

Planar Surfaces ◽

Step Algorithm

A direct, efficient method for the problem of epipolar rectification in the uncalibrated casewas proposed. The method was based on minimizing a measure ofdistortion, by introducing anepipolar distance transform. The transform converted image intensity values to a relative locationinside a planar segment along the epipolar line, so it was robust to noises. The ratio of the distancesbetween two matching points in the epipolar lines was theoretically proved invariant to an affinetransformation for planar surfaces. To calculate the relative rotation between both cameras, thealgorithm was decomposed into three-steps to limit the distortion. Results show that the new measureis more appropriate for image rectification, and the three-step algorithm has obtained an accuracycomparable result both in estimation error and visual effect, especially when the initial epipolar linesare far from horizontal.

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