Location measuring device and method

• US 7,787,689 B2
• Filed: 07/02/2008
• Issued: 08/31/2010
• Est. Priority Date: 07/06/2007
• Status: Active Grant

• Current Assignee: Topcon Corporation
• Original Assignee: Topcon Corporation
• Inventors: Kochi, Nobuo, Anai, Tetsuji, Otani, Hitoshi
• Primary Examiner(s): AZARIAN, SEYED H
• Application Number:
  US12/166,654
• Publication Number:
  US 20090175497A1
• Time in Patent Office: 790 Days
• Field of Search: 382/100, 382/103, 382/104, 382/106, 382/107, 382/154, 382/168, 382/181, 382190-194, 382/199, 382/209, 382/232, 382/254, 382/274, 382/276, 382/286, 382291-295, 382/305, 382/312, 348/218.1, 348/188, 348/207.99, 348/223.1, 348/187, 348/129, 396/55
• US Class Current: 382/154
• CPC Class Codes: G06T 2200/08 involving all processing steps from image acquisition to 3D model generation
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 7/579 from motion
• CPC Class Codes: G06T 7/74 involving reference images or patches

Abstract

With apparatus and method for measuring in three dimensions by applying an estimating process to points corresponding to feature points in a plurality of motion image frames, high speed and high accuracy are realized. The apparatus comprises: a first track determining section (4B) that determines corresponding points of feature points extracted from frames of motion images and estimates by robust estimation a coordinate transformation projection parameters between frames using part of the determined corresponding points, a second track determining section (4C) that utilizes the estimated value to determine coordinate values of estimated location of each corresponding point, to determine residuals of the coordinate values relative to the estimated values for each corresponding point, to apply threshold process, and to exclude points of large residuals as incorrect corresponding points. Three-dimensional measurement is carried out by tracking again feature points while removing those incorrect corresponding points.

Claims

1. A location measuring device comprising:

a feature point extracting section for extracting a plurality of feature points on a photographing object from each of successively photographed images in a plurality of frames obtained with an image obtaining means, a location of the image obtaining means relatively varying to a location of the photographing object with time;

a feature point tracking section for searching each of the successively photographed images for points corresponding to the feature points and tracking the feature points;

a first track determining section for applying robust estimation to residuals, each of the residuals being a residual of a coordinate calculated by using a set of projection parameters between one and another images on a basis of locational relationship between the feature points on the one and the another images from a process of the tracking or results of the tracking by the feature point tracking section and determining an estimated value of the projection parameters;

a second track determining section for determining a residual between a coordinate of the corresponding point corresponding to each of the feature points and an estimated coordinate of the corresponding point by utilizing the estimated value of the projection parameters determined with the first track determining section, applying a threshold process, determining whether or not the each of feature points is incorrect corresponding point, and removing the incorrect corresponding point from the feature points;

a template re-matching section for determining an estimated coordinate of the corresponding point by utilizing the estimated value of the projection parameters determined with the first track determining section, and carrying out template matching in a vicinity of the estimated coordinate to determine a coordinate of each of appropriate corresponding points, and

a location measuring section for measuring a coordinate of the photographing object, or the location or a photographing posture of the image obtaining means on a basis of coordinates of the corresponding points other than the incorrect corresponding points determined with the second track determining section and on a basis of the coordinates of the appropriate corresponding points determined with the template re-matching section.

2. The location measuring device as recited in claim 1, wherein the robust estimation is one of:

LMedS method, median estimation (M estimation) method, and RANSAC (random sample consensus) method.

3. The location measuring device as recited in claim 1, wherein the first track determining section determines a set of projection parameters between the photographed images from a plurality of partial feature points chosen out of the plurality of feature points extracted, calculates coordinates of corresponding points of feature points other than the partial feature points, and determines residuals of the coordinates of the feature points on a basis of the coordinates.

4. The location measuring device as recited in claim 3, wherein the robust estimation employed in the first track determining section is LMedS method:

to determine a median of magnitudes of difference in the coordinates for each corresponding point on a basis of the set of projection parameters determined from the partial corresponding points;

in which a same process is applied to combinations of other partial corresponding points;

to choose a combination of the partial corresponding points that minimizes the determined median; and

to determine the projection parameters.

5. The location measuring device as recited in claim 1, wherein the projection parameters in the first track determining section are affine transformation parameters.

6. The location measuring device as recited in claim 1, comprising a GPS location data acquiring section for acquiring photographing location data from GPS data and an operating section for determining correlation between the photographing location data acquired and the photographing location data of respective frame determined in the location measuring section.

7. A location measuring method comprising:

a feature point extracting step of extracting a plurality of feature points on a photographing object from each of successively photographed images in a plurality of frames obtained with an image obtaining means, a location of the image obtaining means relatively varying to a location of the photographing object with time;

a feature point tracking step of searching each of the successively photographed images for points corresponding to the feature points and tracking the feature points;

a first track determination step of applying robust estimation to residuals, each of the residuals being a residual of a coordinate calculated by using the projection parameters between one and another images on a basis of locational relationship between the feature points on the one and another images from a process of the tracking or results of the tracking in the feature point tracking step and determining an estimated value of the projection parameters;

a second track determining step of determining a residual between a coordinate of the corresponding point corresponding to each of the feature points and an estimated coordinate of the corresponding point by utilizing the estimated value of the projection parameters determined in the first track determining step, applying a threshold process, determining whether or not the each of feature points is incorrect corresponding point, and removing the incorrect corresponding point from the feature points;

a template re-matching step of determining an estimated coordinate of the corresponding point by utilizing the estimated value of the projection parameters determined in the first track determination step , and carrying out template matching in a vicinity of the estimated coordinate to determine a coordinate of each of appropriate corresponding points, and

a location measuring step of measuring a coordinate of the photographing object, or the location or a photographing posture of the image obtaining means on a basis of coordinates of the corresponding points other than the incorrect corresponding points determined in the second track determining step and on a basis of the coordinates of the appropriate corresponding points determined in the template re-matching step.