APPARATUS AND METHOD FOR EXTRACTING CORRESPONDENCES BETWEEN AERIAL IMAGES

• US 20120155745A1
• Filed: 12/14/2011
• Published: 06/21/2012
• Est. Priority Date: 12/16/2010
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Chu, Chang-Woo, Cha, Young-Mi, Koo, Bon-Ki, PARK, Il-Kyu
• Granted Patent: US 9,390,330 B2
• Time in Patent Office: Days
• US Class Current: 382/154
• CPC Class Codes: G06T 17/05 Geographic models
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 2207/30184 Infrastructure
• CPC Class Codes: G06T 7/33 using feature-based methods
• CPC Class Codes: G06V 20/176 Urban or other man-made structures

Abstract

Disclosed herein is an apparatus and method for extracting correspondences between aerial images. The apparatus includes a line extraction unit, a line direction determination unit, a building top area extraction unit, and a correspondence extraction unit. The line extraction unit extracts lines corresponding buildings from aerial images. The line direction determination unit defines the directions of the lines as x, y and z axis directions based on a two-dimensional (2D) coordinate system. The building top area extraction unit rotates lines in the x and y axis directions so that the lines are arranged in parallel with the horizontal and vertical directions of the 2D image, and then extracts building top areas from rectangles. The correspondence extraction unit extracts correspondences between the aerial images by comparing the locations of the building top areas extracted from the aerial images.

Claims

1. An apparatus for extracting correspondences between aerial images, comprising:

a line extraction unit for extracting lines corresponding buildings from two or more aerial images;

a line direction determination unit for defining directions of the lines as x, y and z axis directions based on a coordinate system of a two-dimensional (2D) image;

a building top area extraction unit for rotating lines in the x axis direction and lines in the y axis direction so that the lines in the x axis direction are arranged in parallel with a horizontal direction of the 2D image and the lines in the y axis direction are arranged in parallel with a vertical direction of the 2D image, and then extracting building top areas from rectangles that are formed by the rotation; and

a correspondence extraction unit for extracting correspondences between the aerial images by comparing locations of the building top areas extracted from the aerial images.

2. The apparatus as set forth in claim 1, wherein the line extraction unit extracts lines corresponding to edges and contours of the buildings from among lines that are selected from among the lines of the aerial images and fall within a preset reference range.

3. The apparatus as set forth in claim 1, wherein the line direction determination unit creates a direction distribution histogram of the lines, and defines directions having three highest peak values in the direction distribution histogram as x, y, and z axis directions, respectively.

4. The apparatus as set forth in claim 3, wherein the line direction determination unit defines one of the highest peak value directions closest to a vertical direction as the z axis direction and two remaining highest peak value directions as the x and y axis directions, respectively.

5. The apparatus as set forth in claim 4, wherein the line direction determination unit defines an arbitrary one of the two remaining highest peak value directions as the x axis direction and a remaining highest peak value direction as the y axis direction.

6. The apparatus as set forth in claim 1, wherein the building top area extraction unit, when each of the building top areas is not a rectangle, creates a rectangle by extending the lines in the x and y axis directions.

7. The apparatus as set forth in claim 1, wherein the correspondence extraction unit defines central points of the building top areas as feature points and extracts correspondences between the aerial images based on locations of the feature points and the edges of the building top areas.

8. The apparatus as set forth in claim 7, further comprising a transformation matrix calculation unit for calculating a transformation matrix according to rotation and translation transformation of the buildings between the aerial images, from sums of squares of distances between coordinates of the feature points of the aerial images.

9. The apparatus as set forth in claim 8, wherein the correspondence extraction unit extracts corresponding points of another aerial image for the feature points using the transformation matrix, and compares locations of the feature points with locations of the corresponding points of the latter aerial image.

10. A method of extracting correspondences between aerial images, comprising:

extracting lines corresponding buildings from two or more aerial images;

defining directions of the lines as x, y and z axis directions based on a coordinate system of a 2D image;

rotating lines in the x axis direction and lines in the y axis direction so that the lines in the x axis direction are arranged in parallel with a horizontal direction of the 2D image and the lines in the y axis direction are arranged in parallel with a vertical direction of the 2D image, and then extracting building top areas from rectangles that are formed by the rotation; and

extracting correspondences between the aerial images by comparing locations of the building top areas extracted from the aerial images.

11. The method as set forth in claim 10, wherein the extracting lines extracts lines corresponding to edges and contours of the buildings from among lines that are selected from among the lines of the aerial images and fall within a preset reference range.

12. The method as set forth in claim 10, wherein the defining comprises creating a direction distribution histogram of the lines, and defines directions having three highest peak values in the direction distribution histogram as x, y, and z axis directions, respectively.

13. The method as set forth in claim 12, wherein the defining defines one of the highest peak value directions closest to a vertical direction as the z axis direction and two remaining highest peak value directions as the x and y axis directions, respectively.

14. The method as set forth in claim 13, wherein the defining defines an arbitrary one of the two remaining highest peak value directions as the x axis direction and a remaining highest peak value direction as the y axis direction.

15. The method as set forth in claim 10, wherein the extracting building top areas comprises, when each of the building top areas is not a rectangle, creating a rectangle by extending the lines in the x and y axis directions.

16. The method as set forth in claim 10, wherein the extracting correspondences comprises defining central points of the building top areas as feature points, and extracts correspondences between the aerial images based on locations of the feature points and the edges of the building top areas.

17. The method as set forth in claim 16, further comprising calculating a transformation matrix according to rotation and translation transformation of the buildings between the aerial images, from sums of squares of distances between coordinates of the feature points of the aerial images.

18. The method as set forth in claim 17, wherein the extracting correspondences further comprises:

extracting corresponding points of another aerial image for the feature points using the transformation matrix; and

comparing locations of the feature points with locations of the corresponding points of the latter aerial image.