Method for producing a depth map

Abstract

A method for producing a depth map from a detection region of the Earth's surface, a detection region being arranged in an underground pipeline, wherein the method includes recording at least one image sequence via at least one camera, determining the position and orientation of the camera corresponding to each individual recording, determining a spatial position and orientation of the underground pipeline arranged in the detection region, producing the depth map of the detection region via a plane sweep method based on the individual recordings and the associated camera positions, where the maximum depth region of the plane sweep method is subdivided into a total of N sections in an adaptive manner, i.e., in accordance with a predetermined minimum layer thickness for the ground covering the underground pipeline, via a predetermined number of planes spaced differently from one another and extending parallel with respect to one another.

Claims

1. A method for compiling a depth map of an acquisition zone at a surface of the Earth, an underground pipeline being arranged in said acquisition zone, the method comprising: capturing at least one image sequence using at least one camera, said image sequence comprising a plurality of at least partly overlapping individual captures of the acquisition zone; determining a position and orientation of the at least one camera corresponding to each individual capture; determining an averaged spatial position and orientation of the underground pipeline arranged in the acquisition zone from reference data; and compiling the depth map of the acquisition zone via a plane-sweep method based on the plurality of at least partly overlapping individual captures and respectively associated camera poses; wherein a maximum depth range of the plane-sweep method is subdivided adaptively into a total of N portions, via a predetermined number of planes spaced differently from one another and extending parallel to one another, such that a predetermined portion height is assigned to each individual one of the N portions; and wherein the orientation of the predetermined number of planes extends parallel to the orientation of the underground pipeline.

2. The method as claimed in claim 1, wherein a portion height of a portion extending in a region of a boundary layer assumes a minimum value and portion heights of further remaining portions arranged at either side of the boundary layer increase from the boundary layer incrementally based on said minimum value; and wherein the region of the boundary layer is determined by subtracting a value of the minimum layer thickness from a depth of the underground pipeline.

3. The method as claimed in claim 2, wherein a spatial position and orientation of the at least one camera is determined via a global navigation satellite system in conjunction with one of (i) structure-from-motion techniques, (ii) visual odometry and (iii) inertial sensors.

4. The method as claimed in claim 2, wherein the orientation of the underground pipeline is determined via measurement data collected while said underground pipeline is being laid.

5. The method as claimed in claim 1, wherein a spatial position and orientation of the camera is determined via a global navigation satellite system in conjunction with one of (i) structure-from-motion techniques, (ii) visual odometry and (iii) inertial sensors.

6. The method as claimed in claim 1, wherein the orientation of the underground pipeline is determined via measurement data collected while said underground pipeline is being laid.

7. The method as claimed in claim 1, wherein the orientation of the underground pipeline is determined via measurement data collected while said underground pipeline is being laid.

8. The method as claimed in claim 1, wherein an averaged spatial position and orientation of the underground pipeline is represented in each individual capture by one point and one vector.

9. The method as claimed in claim 1, wherein the position and orientation of the at least one camera and the spatial position and orientation of the underground pipeline is indicated in a common coordinate system.

10. The method as claimed in claim 9, wherein the common coordinate system comprises one of (i) a Universal Transverse Mercator (UTM) system and (ii) a Gau-Krger coordinate system.

11. The method as claimed in claim 1, wherein an actual layer thickness of soil covering the underground pipeline is measured in the acquisition zone by comparing the compiled depth map with the spatial position and orientation of the underground pipeline in the acquisition zone.

12. The method as claimed in claim 1, wherein the maximum depth range of the plane-sweep method is subdivided adaptively as a function of a predetermined minimum layer thickness for soil covering the underground pipeline.

13. A non-transitory computer program product encoded with a computer program loadable directly into at least one of a memory of a camera and a computing unit assigned to the camera which, when executed by the camera causes compilation of a depth map of an acquisition zone at a surface of the Earth, an underground pipeline being arranged in said acquisition zone, the computer program comprising: program code for capturing at least one image sequence using at least one camera, said image sequence comprising a plurality of at least partly overlapping individual captures of the acquisition zone; program code for determining a position and orientation of the at least one camera corresponding to each individual capture; program code for determining an averaged spatial position and orientation of the underground pipeline arranged in the acquisition zone from reference data; and program code for compiling the depth map of the acquisition zone via a plane-sweep method based on the plurality of at least partly overlapping individual captures and respectively associated camera poses; wherein a maximum depth range of the plane-sweep method is subdivided adaptively into a total of N portions, via a predetermined number of planes spaced differently from one another and extending parallel to one another, such that a predetermined portion height is assigned to each individual one of the N portions; and wherein the orientation of the predetermined number of planes extends parallel to the orientation of the underground pipeline.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in greater detail with reference to an exemplary embodiment. The drawings are shown by way of example and are intended to illustrate the concept of the invention but not in any way to restrict said invention or to constitute a definitive representation thereof, in which:

(2) FIG. 1 shows a schematic front view of an acquisition zone, which acquisition zone is measured by means of a plane-sweep method in accordance with the prior art;

(3) FIG. 2 shows a schematic front view of an acquisition zone, where the acquisition zone is measured via a plane-sweep method in accordance with the invention; and

(4) FIG. 3 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(5) FIG. 1 shows a schematic view of an acquisition zone 1 of the earth's surface. Below a boundary layer 7, which extends between the ground and the atmosphere and thus represents a portion of the earth's surface, an underground pipeline 2 with a specific spatial orientation 4 is arranged. Above the boundary layer 7 are certain raised objects, represented in this specific case as trees.

(6) A camera 3 is in the process of taking an image of the acquisition zone 1, where the camera 3 is mounted on a UAV flying over the acquisition zone at a given height and is directed towards the earth's surface. The conventional plane-sweep method, which is outlined in FIG. 1, then uniformly subdivides a depth range 5, which extends from the camera 3 towards the earth's surface, into equidistant portions via a predetermined number of planes 6. To enable adequate acquisition of irregularities in the height profile of the boundary layer 7, this depth range 5 must extend further than merely from the camera 3 to the boundary layer 7. The depth range 5 should therefore extend at least as far as into the depth range of the underground pipeline 2. The planes 6, by which the depth range 5 is quantized, extend parallel to one another, but not parallel to the orientation 4 of the underground pipeline 2 or parallel to the boundary layer 7.

(7) The number of portions i available for quantizing the depth range 5 is limited, on the one hand, by the computing power of an evaluation unit, which performs the calculations for compiling the depth map and, on the other hand, also by the available memory space of this evaluation unit and is conventionally in the range between 200 and 300. Owing to the accuracy with which the depth map of the acquisition zone 1 has to be compiled, a portion height D.sub.i of the individual portions should be in the lower, one-digit centimeter range. If the portion height D.sub.i amounts, for example, to 1 cm, a depth range 5 of only 2 m can be covered. Objects raised above the boundary layer 7, such as trees or buildings, may however far exceed this 2 m range. In addition, even the incline or slope of the terrain can exceed this depth range.

(8) FIG. 2, on the other hand, outlines the method in accordance with the invention for compiling a depth map of the acquisition zone 1. Here, the acquisition zone 5 is likewise subdivided into portions i via the planes 6. However, on the one hand, the planes 6 extend parallel to the orientation 4 of the underground pipeline 2 while, on the other hand, the portion heights D.sub.i of the individual portions i are not constant.

(9) The planes 6 are oriented and the portion heights D.sub.i selected in the plane-sweep method in accordance with the invention such that initially all the position and spatial orientation 4 of the underground pipeline 2 is determined from reference data, in the specific exemplary embodiment from cadastral data from the construction phase. Viewed from the camera 3, the statutorily specified minimum layer thickness T is then subtracted from the depth T.sub.2 of the pipeline 2 ascertained in this way, in order to estimate the depth T.sub.7, and thus the region, of the boundary layer 7 relative to the origin of the depth range 5.

(10) In this range, a minimum portion height D.sub.i is assigned to a portion i extending parallel to the spatial orientation 4 of the underground pipeline 2. The portion heights D.sub.i of all the other portions i extending above and below this portion i arranged in the region of the boundary layer 7 increase incrementally when observed from the boundary layer 7. In the region of the boundary layer 7, in particular in the region of the admissible tolerance values for the layer thickness of the soil covering the underground pipeline, a very detailed depth map may thus be compiled, with high depth resolution. The depth range 5 may in this case be significantly greater than in the conventional prior art method, because a particularly small portion height D.sub.i, and thus high depth map accuracy, need only be present in the region of the boundary layer 7 and the portion heights D.sub.i of the remaining portions are sometimes markedly greater than this minimum portion height D.sub.i.

(11) FIG. 3 is a flowchart of the method for compiling a depth map of an acquisition zone 1 at the Earth's surface of, where an underground pipeline 2 is arranged in the acquisition zone 1. The method comprises capturing at least one image sequence using at least one camera 3, as indicated in step 310. In accordance with the method of the invention, the image sequence comprises a plurality of at least partly overlapping individual captures of the acquisition zone 1.

(12) Next, the position and orientation of the at least one camera corresponding to each individual capture is determined, as indicated in step 320.

(13) Next, a preferably averaged spatial position and orientation 4 of the underground pipeline 2 arranged in the acquisition zone 1 is determined from reference data, as indicated in step 330. The depth map of the acquisition zone 1 is now compiled via a plane-sweep method based on the plurality of at least partly overlapping individual captures and respectively associated camera poses, as indicated in step 340.

(14) In accordance with the method of the invention, the maximum depth range 5 of the plane sweep method is subdivided adaptively into a total of N portions i, via a predetermined number of planes 6 spaced differently from one another and extending parallel to one another, such that a predetermined portion height D.sub.i is assigned to each individual one of the N portions i, and the orientation of the predetermined number of planes 6 extends parallel to the orientation 4 of the underground pipeline 2.

(15) Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention.

(16) Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.