METHOD AND APPARATUS FOR COMPENSATING LATERAL DISPLACEMENTS AND LOW SPEED VARIATIONS IN THE MEASURE OF A LONGITUDINAL PROFILE OF A SURFACE

• US 20140207411A1
• Filed: 01/21/2013
• Published: 07/24/2014
• Est. Priority Date: 01/21/2013
• Status: Active Grant

• Current Assignee: Systemes Pavemetrics Inc.
• Original Assignee: Systemes Pavemetrics Inc.
• Inventors: LAURENT, John, HABEL, Richard, TALBOT, Mario
• Granted Patent: US 9,267,792 B2
• Time in Patent Office: Days
• US Class Current: 702/159
• CPC Class Codes: G01B 11/06 for measuring thickness ; e.g. of sheet material thickness measurement by thermal means G01B21/085
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01B 11/30 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00

Abstract

Measuring a distance to a surface while compensating for variations in a transverse position and/or low speed displacement of the instrument. One method includes retrieving a predetermined transversal distance from a longitudinal feature at which to extract a relevant distance; retrieving a distance set; retrieving a position of the longitudinal feature relative to the distance set; extracting a range point at the predetermined transversal distance from the longitudinal feature; adding the extracted point to a longitudinal distance set. In another method, if two sensors are provided with an overlap in the transversal direction, extracting a range point at a predetermined transversal position; adding the extracted range point to a longitudinal distance set; retrieving a pitch angle of the instrument; calculating a local slope of the surface using an overlapping transversal point, the pitch angle and the separation length; calculating a height variation using the local slope and a longitudinal separation.

Claims

1. A system for measuring a distance to a surface along a longitudinal direction of said surface using an acquisition instrument while compensating for variations in a transverse position of the acquisition instrument, said surface having a longitudinally-aligned feature, said system comprising:

an acquisition instrument including a multipoint range sensor acquiring said distance between said acquisition instrument and said surface, said multipoint range sensor acquiring said distance in a field of view of said acquisition instrument at a multitude of transversal points, thereby acquiring a distance set, said field of view having a transversal dimension and a longitudinal dimension along said longitudinal direction of said surface, said transversal dimension being longer than said longitudinal dimension;

a translation mechanism for displacing said acquisition instrument to allow said acquisition instrument to acquire said distance set at a plurality of positions along said longitudinal direction;

a processor for;

retrieving a position of said longitudinally-aligned feature of the surface relative to the field of view of the acquisition instrument;

retrieving a predetermined transversal distance from said longitudinally-aligned feature at which to extract a relevant distance from said distance set;

extracting a range point in said distance set at said predetermined transversal distance from said position of said longitudinally-aligned feature;

adding the extracted range point to generate a longitudinal distance set at a constant transversal distance from said longitudinal feature.

2. The system as claimed in claim 1, wherein said translation mechanism is a vehicle and said surface is one of a road, an airport runway, a tunnel lining and a train track.

3. The system as claimed in claim 1, wherein said multipoint range sensor is one of a triangulation based laser line profiler, a scanning point laser profiler and a lidar based scanning point laser profiler.

4. The system as claimed in claim 1, wherein said longitudinal feature is at least one of a road lane marking, a road edge, a curb, a joint, a concrete slab edge, a road wheel path position, a road rut shape, a rail and a rail tie.

5. The system as claimed in claim 1, said processor further being for retrieving an image, wherein said retrieving said position of the longitudinally-aligned feature comprises detecting a location of said longitudinal feature in said image.

6. The system as claimed in claim 1, wherein said retrieving said position of the longitudinally-aligned feature comprises detecting a location of said longitudinal feature in said distance set generated by the multipoint range sensor using said distance between said instrument and said surface at said longitudinally-aligned feature.

7. The system as claimed in claim 1, wherein said acquisition instrument further comprises an elevation sensor for measuring a total elevation of both said surface and said acquisition instrument at least at said predetermined transversal distance from said position of said longitudinally-aligned feature;

said processor further being for subtracting said distance between said acquisition instrument and said surface acquired by said acquisition instrument from said total elevation measured by said elevation sensor to determine a surface elevation of the surface and for adding the surface elevation to generate a surface elevation set at a constant transversal distance from said longitudinal feature.

8. The system as claimed in claim 7, wherein said elevation sensor is one of a multi-axis accelerometer, a vertically oriented single axis accelerometer, an inertial measurement unit (IMU) and a global positioning system (GPS) receiver.

9. The system as claimed in claim 1, wherein said acquisition instrument includes a pitch finder, said pitch finder being adapted to measure a pitch angle of said acquisition instrument in the longitudinal direction versus gravity, wherein said multipoint range sensor includes two multipoint range sensors, said two multipoint range sensors being a first sensor with a first field of view and a second sensor with a second field of view, said first field of view partly overlapping said second field of view in the transversal direction at an overlap, said first field of view being separated by a separation length from said second field of view at said overlap in said longitudinal direction;

wherein said processor is further adapted to determine a surface elevation of the surface using the pitch angle and an overlapping transversal point in said overlap in said first field of view and in said second field of view and said separation length and for adding the surface elevation to generate a surface elevation set at a constant transversal distance from said longitudinal feature.

10. A method for measuring a distance to a surface along a longitudinal direction of said surface using an acquisition instrument while compensating for variations in a transverse position of the acquisition instrument, said surface having a longitudinally-aligned feature, said method comprising:

retrieving a predetermined transversal distance from said longitudinally-aligned feature at which to extract a relevant distance;

for each position of a plurality of positions along said longitudinal direction,

retrieving a distance set including a multitude of transversal points, said transversal points each being a distance between said acquisition instrument and said surface along a transversal direction;

retrieving a position of said longitudinally-aligned feature of the surface relative to the distance set;

extracting a range point in said distance set at said predetermined transversal distance from said position of said longitudinally-aligned feature;

adding the extracted range point to generate a longitudinal distance set at a constant transversal distance from said longitudinal feature.

11. The method as claimed in claim 10, wherein said retrieving said position of the longitudinally-aligned feature comprises detecting a location of said longitudinal feature in an image.

12. The method as claimed in claim 11, wherein said detection a location of said longitudinal feature in an image includes using an intensity of said longitudinally-aligned feature in one of a grey-scale image, a color image and a range image.

13. The method as claimed in claim 10, wherein said retrieving said position of the longitudinally-aligned feature comprises detecting a location of said longitudinal feature in said distance set using said distance between said instrument and said surface at said longitudinally-aligned feature.

14. The method as claimed in claim 10, further comprising:

retrieving a total elevation of both said surface and said acquisition instrument at least at said predetermined transversal distance from said position of said longitudinally-aligned feature;

subtracting said distance between said acquisition instrument and said surface from said total elevation to determine a surface elevation of the surface;

adding the surface elevation to generate a surface elevation set at a constant transversal distance from said longitudinal feature.

15. The method as claimed in claim 14, further comprising:

combining said surface elevation set and said longitudinal distance set to create a longitudinal 3D profile.

16. The method as claimed in claim 10,

wherein said retrieving said distance set includes retrieving a first distance set and a second distance set, at least a portion of said transversal points of said first distance set being aligned transversally with at least a portion of said transversal points of said second distance set thereby creating a transversal overlap of said first and second distance sets, said first distance set and said second distance set being acquired at separate positions along said longitudinal direction, said separate positions being separated by a separation length;

retrieving a pitch angle of said acquisition instrument in the longitudinal direction versus gravity;

calculating a local slope of said surface using an overlapping transversal point in said transversal overlap in said first distance set and in said second distance set, said pitch angle and said separation length;

calculating a height variation using said local slope and a longitudinal distance between consecutive ones of said plurality of positions along said longitudinal direction;

adding the height variation to generate a surface height set at a constant transversal distance from said longitudinal feature.

17. The method as claimed in claim 16, further comprising:

combining said surface height set and said longitudinal distance set to create a longitudinal 3D profile.

18. A system for measuring a distance to a surface along a longitudinal direction of said surface using an acquisition instrument while compensating for low speed variations of the acquisition instrument, said system comprising:

an acquisition instrument including;

a pitch finder, said pitch finder being adapted to measure a pitch angle of said acquisition instrument in the longitudinal direction versus gravity;

two multipoint range sensors, said two multipoint range sensors including a first sensor and a second sensor, said first multipoint range sensor acquiring said distance between said acquisition instrument and said surface in a first field of view at a first multitude of transversal points, thereby acquiring a first distance set, said second multipoint range sensor acquiring said distance between said acquisition instrument and said surface in a second field of view at a second multitude of transversal points, thereby acquiring a second distance set, said first and second field of view having a transversal dimension and a longitudinal dimension along said longitudinal direction of said surface, said transversal dimension being longer than said longitudinal dimension, said first field of view partly overlapping said second field of view in the transversal direction at an overlap, said first field of view being separated by a separation length from said second field of view at said overlap in said longitudinal direction;

a translation mechanism for displacing said acquisition instrument to allow said acquisition instrument to acquire said first and second distance set at a plurality of positions along said longitudinal direction;

a processor for;

extracting a range point in said first distance set at a predetermined transversal position;

adding the extracted range point to generate a longitudinal distance set;

determining a surface elevation of the surface using the pitch angle and an overlapping transversal point in said overlap in said first field of view and in said second field of view and said separation length;

adding the surface elevation to the longitudinal distance set to generate a surface elevation set.

19. A method for measuring a distance to a surface along a longitudinal direction of said surface using an acquisition instrument while compensating for low speed variations of the acquisition instrument, said method comprising:

for each position of a plurality of positions along said longitudinal direction,

retrieving a first distance set including a first multitude of transversal points and a second distance set including a second multitude of transversal points, said transversal points each being a distance between said acquisition instrument and said surface along a transversal direction, at least a portion of said transversal points of said first distance set being aligned transversally with at least a portion of said transversal points of said second distance set thereby creating a transversal overlap of said first and second distance sets, said first distance set and said second distance set being acquired at separate positions along said longitudinal direction, said separate positions being separated by a separation length;

extracting a range point in said first distance set at a predetermined transversal position;

adding the extracted range point to generate a longitudinal distance set;

retrieving a pitch angle of said acquisition instrument in the longitudinal direction versus gravity;

calculating a local slope of said surface using an overlapping transversal point in said transversal overlap in said first distance set and in said second distance set, said pitch angle and said separation length;

calculating a height variation using said local slope and a longitudinal distance between consecutive ones of said plurality of positions along said longitudinal direction;

adding the height variation to the longitudinal distance set to generate a surface height set.