JP5749965B2 - Reference scale for measuring features on the image - Google Patents

Description

  The present invention relates to a reference scale used in on-image feature measurement for measuring a feature captured in an image obtained by photographing with a camera.

  One of the techniques using an image (image data) obtained by photographing with a digital camera is image top feature measurement. In the on-image feature measurement, the width, height, depth, and the like are measured for various features such as buildings and roads captured in the image by the camera. For such image top feature measurement, there is known a measurement method called a vanishing point method (Patent Document 1). In the vanishing point method, the feature on the image is measured based on the vanishing point on the image. Specifically, the vanishing point is first obtained using the outline of an appropriate feature captured in the image. Then, based on the vanishing point, the actual length per pixel in the desired measurement site of the target feature to be measured is obtained, and the feature on the image is measured based on the actual length per pixel.

  In such vanishing point image top feature measurement, it is possible to perform measurement more efficiently by using a teacher line whose absolute length on the image is known. That is, in the technique using the teacher line, the teacher line is generated in the feature measurement image, and the measurement line and the teacher line designated for the desired measurement part of the feature on the measurement target image are converted into the vanishing point. Measurement can be performed by comparing the number of pixels under the relative positional relationship between the measurement line and the teacher line with respect to, thus greatly reducing the processing burden for measurement and making measurement more efficient. Can be done. The teacher lines in this case are generated for the X, Y, and Z coordinate axes of the three-dimensional coordinates in the subject space of the feature measurement image. That is, each of the teacher lines is generated as an X-axis direction teacher line, a Y-axis direction teacher line, and a Z-axis direction teacher line. According to Patent Document 1, a linear body having a known length, that is, a reference scale is taken into an image and generated as an image of the reference scale. The case where is used is described.

JP 2009-229182 A

  As described above, in the vanishing point type image top feature measurement, it is possible to perform the measurement more efficiently by using the teacher line. However, in order to make the measurement efficiency of the teacher line more practical, there remains a problem in generating the teacher line in the feature measurement image. That is, conventionally, a surveying pole is incorporated into an image in order to generate a teacher line in an image for feature measurement. The surveying pole usually has a length of 2 m or more. Therefore, in order to generate teacher lines for the X, Y, and Z coordinate axes of the three-dimensional coordinates in the subject space of the feature measurement image, three survey poles of 2 m or more are used, and these are measured in a three-dimensional coordinate manner. It is necessary to have the image taken into the image. This increases the work burden associated with capturing an image for measuring a feature, and as a result, it is impossible to obtain the improvement in measurement efficiency by using a teacher line. In other words, the method of using a surveying pole as a reference scale for generating a teacher line leaves problems in terms of the handling of the reference scale and the workability of generating the teacher line. It means that the fruit of improvement was not obtained.

  Moreover, the method of generating a teacher line with a surveying pole has a problem regarding the accuracy of the actual length per pixel in the teacher line. In the method using the teacher line, the actual length per pixel in the desired measurement region of the feature is obtained based on the actual length per pixel of the teacher line. For this reason, the accuracy of the actual length per pixel of the teacher line is directly linked to the accuracy of the feature measurement. Therefore, it is desired for the teacher line to obtain as high accuracy as possible in the actual length per pixel. However, the survey pole usually has a scale unit of 20 cm in length, and cannot always sufficiently satisfy the demand for the teacher line as described above.

  The present invention has been made in the background of the above circumstances, and its problem is that it is excellent in handling and workability related to teacher line generation and more accurate for teacher line generation in image top feature measurement. It is to provide a reference scale that enables generation of high teacher lines.

  In order to solve the above-mentioned problem, in the first invention, an image upper ground formed by measuring a feature captured in the image on an image obtained by photographing with a camera based on a vanishing point obtained on the image. In the object measurement, in the reference scale for image upper object measurement used to generate a teacher line whose absolute length is known on the image for measurement based on the vanishing point, the subject of the image X-direction scale, Y each of which is combined so as to extend corresponding to the X, Y, and Z coordinate axes of three-dimensional coordinates in space, and each is provided with a scale indicating the known absolute length, Y A directional scale and a Z-direction scale are provided.

  Such a reference scale according to the first invention is easy to handle and is excellent in workability relating to teacher line generation. In other words, the reference scale according to the first invention includes X, Y, and Z direction scales combined to correspond to the X, Y, and Z coordinate axes of the three-dimensional coordinates in the subject space of the feature measurement image. ing. For this reason, for example, when measuring features along the road, it is only necessary to shoot the image along the road with the reference scale placed on the road so that it can be captured in the feature measurement image in an appropriate arrangement. It is very easy to handle and has excellent workability for teacher line generation.

  In the reference scale according to the first invention, length scales are provided on the X, Y, and Z direction scales. And about the length scale, for example, it is possible to provide a scale of 10 cm as a large scale, a scale of 5 cm as a middle scale, and a scale of 1 cm as a fine scale. By making such a scale structure, It is possible to generate a teacher line with higher accuracy of the manifestation length per pixel.

  According to a second aspect of the present invention, the reference scale as described above is characterized in that the X-direction scale, the Y-direction scale, and the Z-direction scale are combined in a foldable manner.

  In the feature measurement on the image, the user goes to various places to photograph the feature measurement image, and carries the reference scale at that time. Therefore, the reference scale is required to have excellent portability. About this, since the reference | standard scale by 2nd invention combines each direction scale of X, Y, and Z so that folding is possible, it can carry in the state folded compactly, and it was excellent in the requirement of portability. I can respond.

  In the third invention, with respect to the reference scale as described above, the X-direction scale, the Y-direction scale, and the Z-direction scale are each formed to have four side surfaces, and at least of the four side surfaces. The scale is provided on three side surfaces.

  In such a reference scale of the third invention, since the scale is provided on each of the three side surfaces of each of the X, Y, and Z direction scales, the direction of the reference scale when the feature measurement image is taken in The degree of freedom is increased, and it is possible to more easily calculate the manifestation length per pixel based on the scales in the X, Y, and Z direction scales.

  According to the present invention as described above, there is a reference scale that is superior in handling and workability related to teacher line generation, and that can generate a teacher line with higher accuracy, for teacher line generation in image top feature measurement. can get.

It is a figure which simplifies and shows the structure in the expansion | deployment state of the reference | standard scale by one Example. It is a figure which simplifies and shows the structure in the folding state of the reference | standard scale by one Example. It is a figure which shows the structure of the feature data acquisition system used by image top feature measurement. It is a figure which shows the flow of an image top feature measurement process. It is a figure explaining designation | designated of a road side line and a measurement line. It is a figure which shows the example of the three-dimensional coordinate in to-be-photographed space. It is a figure explaining the principle about calculation of the X-axis component of a measurement line. It is a figure explaining the principle about calculation of the Y-axis component of a measurement line. It is a figure explaining the principle about calculation of the Z-axis component of a measurement line. It is a figure which shows the example of a measurement area | region. It is a figure which shows the example of image data with feature data.

  FIG. 1 and FIG. 2 show a simplified configuration of a reference scale for image top feature measurement according to one embodiment. FIG. 1 shows the unfolded state when in use, and FIG. 2 shows the folded state when not in use. As shown in FIG. 1, the reference scale 31 of the present embodiment includes an X-direction scale 32, a Y-direction scale 33, and a Z-direction scale 34. And the right X-direction scale 32R. The Z-direction scale 34 is also formed as a left-right Z-direction scale 34L and a right-side Z-direction scale 34R.

  Each of the X, Y, and Z direction scales 32, 33, and 34 is formed in a square bar shape having four side surfaces by using a material having sufficient rigidity and light weight, for example, an aluminum square pipe material. The feature measurement image 4 (FIG. 5), which will be described later, is combined with each other so as to extend corresponding to the X, Y, and Z coordinate axes of the three-dimensional coordinates in the subject space, and can be folded. It is combined. More specifically, the left X-direction measure 32L and the left Z-direction measure 34L are connected to the left X-direction measure 32L by the hinge portion 35L at their base ends so as to be rotatable as indicated by the arrow XL. The X / Z-direction measure unit 36L is formed, and the right X-direction measure 32R and the right Z-direction measure 34R can be rotated as indicated by the arrow XR to the right X-direction measure 32R by the hinge portion 35R at the respective base ends. The right side X / Z direction scale unit 36R is formed by connecting the left side X / Z direction scale unit 36L and the right side X / Z direction scale unit 36R at the base end of the Y direction scale 33. Are connected by a hinge structure (not shown) so that the Y-direction scale 33 can be rotated as indicated by an arrow Y. 2 is folded by the rotation of the arrow XL of the left X-direction scale 32L, the rotation of the arrow XR of the right X-direction scale 32R, and the rotation of the arrow Y of the Y-direction scale 33 in such a connection structure, as shown in FIG. The folded state can be taken.

  The X, Y, and Z direction scales 32, 33, and 34 are used to give absolute lengths to the teacher lines (teacher lines LTx, LTy, and LTz in FIG. 6) generated on the image 4 as described later. The scale 37 is provided for each. The scale 37 is provided as a large scale 37a in units of 10 cm, a medium scale 37b in units of 5 cm, and a small scale 37c in units of 1 cm, and four side surfaces of the X, Y, and Z direction scales 32, 33, and 34, respectively. Are provided on three side surfaces.

  Here, the lengths of the Y-direction scale 33 and the Z-direction scale 34 are about 30 cm, the X-direction scale 32 is about 20 cm long for the left X-direction scale 32L and the right-side X-direction scale 32R, The total length is about 40 cm. It can be said that the length sizes of the X, Y, and Z direction scales 32, 33, and 34 in the reference scale 31 are significantly shorter than those of the surveying pole. In other words, in the reference scale 31, the lengths of the X, Y, and Z direction scales 32, 33, and 34 can be reduced to about 30 cm to 40 cm, thereby achieving compactness. This is because the knowledge obtained by repeating various experiments, that is, the above-described structure of the reference scale 31, particularly the above-described structure related to the scale 37, allows each of the X, Y, and Z direction scales 32, This is based on the knowledge that it is possible to generate a sufficiently accurate teacher line even if the length of 33 and 34 is about 30 cm to 40 cm.

  Hereinafter, an example of image top feature measurement to which the reference scale 31 as described above is applied will be described. FIG. 3 shows the configuration of the feature data acquisition system 1 used in the image top feature measurement according to an example. The feature data acquisition system 1 in this example acquires a roadside image 4 as an image while driving the photographing vehicle 3 on the road 2, and obtains feature data by measuring the feature in the roadside image 4 And consists of a photographing vehicle 3 and an image top feature measurement system 5.

  The photographing vehicle 3 is configured by mounting a digital camera 6 and a photographing management system 7 on a vehicle that can travel even in an urban area where a narrow road with a width of 4 m or less is complicated, for example.

  The camera 6 is a digital still camera or video camera. Usually, a still camera is used, and two cameras are mounted as a front shooting camera 6f and a rear shooting camera 6r. The front photographing camera 6f performs photographing in the state where the optical axis is along the traveling direction in front of the photographing vehicle 3, and the rear photographing camera 6r has the optical axis in the traveling direction behind the photographing vehicle 3. Take a picture along the line. The roadside image 4 obtained by photographing with the front photographing camera 6f and the rear photographing camera 6r is an image in which the road is captured while extending in the optical axis direction. In this way, the front and rear of the traveling direction can be photographed because the front photographing camera 6 f may be backlit depending on the traveling direction of the photographing vehicle 3, so that such a case can be dealt with. It is to make it.

  The imaging management system 7 includes each subsystem of a positioning system 8, an imaging control system 9, and an image data management system 10. The positioning system 8 functions to acquire position and orientation information, which is information about the current position and traveling direction of the photographing vehicle 3, more specifically, the optical axis direction of the camera 6, at intervals of, for example, every traveling distance 1m. . Therefore, the positioning system 8 is configured by combining a GPS (Global Positioning System) and a distance / inertia measurement system. The GPS acquires position / orientation information by receiving signals from a satellite with two GPS antennas 11 provided before and after the photographing vehicle 3. On the other hand, the distance / inertia measurement system includes an inertial measuring device that detects a traveling direction of the photographing vehicle 3 and an inclination of the vehicle with respect to a horizontal plane by a gyro and a distance measuring device that detects a traveling distance of the photographing vehicle 3, and thereby includes position direction information. To get.

  The imaging control system 9 controls imaging by the camera 6 as control that can acquire the roadside images 4 at regular distance intervals. Specifically, the traveling distance of the photographing vehicle 3 is counted, and a photographing command is output for every certain traveling distance such as 5 m to cause the camera 6 to perform photographing. By such photographing, a series of roadside images can be acquired at a constant distance along the road on which the photographing vehicle 3 travels.

  The image data management system 10 is configured by using a workstation-level data processing device, and manages data of the roadside image 4 acquired by photographing by the camera 6. The management is performed by associating the roadside image 4 with the position and orientation information at the time of photographing.

  Here, in the roadside image 4, a teacher line LT necessary for image upper feature measurement processing as described later is generated. The teacher line LT is an image of the roadside image 4 with a direction along the side line of the road 2 in the roadside image 4 (this is used as an outline of a feature for obtaining a vanishing point as described later) as one coordinate axis. Each coordinate axis of three-dimensional coordinates (X, Y, Z coordinates) in the subject space is generated. That is, the teacher line LTx in the X-axis direction, the teacher line LTy in the Y-axis direction, and the teacher line LTz in the Z-axis direction are generated. These teacher lines LTx, LTy, and LTz are based on the images of the X, Y, and Z direction scales 32, 33, and 34 on the reference scale 31 by incorporating the above-described reference scale 31 into the roadside image 4. Generate. In principle, it is sufficient to generate such a teacher line LT only for a roadside image that is first captured under the shooting conditions for a range in which a roadside image is shot under the same shooting conditions. However, practically, it is preferable to generate a teacher line by imprinting a linear body for a teacher line for each road-side image taken at the beginning of a day's shooting work, for example. This is because the setting state of the camera 6 on the photographing vehicle 3 affects the photographing conditions, and the setting state may be slightly different for each day of photographing work.

  The image top feature measurement system 5 is configured by mounting the image top feature measurement means 13 configured as a computer program on the data processing device 12. The on-image feature measuring means 13 manages the roadside image with feature data as described later in which the data of the roadside image 4 captured from the image data management system 10 or the feature data is recorded in the roadside image 4. The data management unit 14, the measurement unit 15 that measures the features captured in the roadside image 4 and acquires the feature data, and records the feature data acquired by the measurement unit 15 in the roadside image 4 A feature data recording unit 16 for generating an image along the road with object data is included.

  Hereinafter, an example of the image upper feature measurement process performed by the image upper feature measurement system 5 will be described. The image top feature measurement processing in this example is a case where the vanishing point is obtained by using the side line of the road 2 in the road-side image 4 as the contour of the feature. As shown in FIG. Each process of S8 is included.

  First, in step S1, a processing target image is displayed. The processing target image display process is a process of displaying the roadside image to be measured on the display screen of the data processing device 12, and is performed in response to designation by the user, or a series of roadside images are sequentially displayed. Is done.

  In step S2, a road side line is designated. Specifically, the user designates a road side line for the roadside image displayed in step S1. The designation is performed as shown in FIG. 5, for example. Specifically, the two designated lines LI and LI are drawn by tracing the side line of the road 2 in the roadside image 4 displayed on the display screen with the drawing function for each of the corresponding straight line portions on the left and right. To do.

  In step S3, vanishing point determination processing is performed. When the vanishing point is obtained using the side line of the road 2, the vanishing point is the intersection V of the two designated lines LI and LI. Therefore, the vanishing point is specified by obtaining the position of the intersection V on the road-side image 4. Specifically, the two-dimensional coordinates on the image with the horizontal direction of the road-side image 4 (corresponding to the horizontal direction in the subject space of the road-side image 4) as the x-axis and the vertical direction as the y-axis are set in the road-side image 4. Then, the position of the intersection V on the road-side image 4 is obtained as the coordinate value (xv, yv) in the two-dimensional coordinates on the image, and this is used as the vanishing point. In FIG. 5, the two-dimensional coordinates on the image are set so that the x-axis is parallel to the teacher line LTx in the X-axis direction.

  In step S4, measurement line designation processing for the measurement region is performed. This processing is performed by drawing the measurement line S on the measurement site by the drawing function as in the example shown in FIG. 5 or by specifying the end points A and B at both ends of the measurement site.

  In step S5, measurement processing of the measurement line specified in step S4 is performed. This measurement process is performed on the premise of three-dimensional coordinates in the subject space of the roadside image as in the example shown in FIG. Here, regarding the three-dimensional coordinates, the horizontal direction is the X axis, the depth direction is the Y axis, and the vertical direction is the Z axis. If such three-dimensional coordinates are assumed, there are two measurement lines depending on the orientation that the measurement line takes on the image along the road and the case where there is only one component in each of the X, Y, and Z axial directions. There may be three combinations. In the case of a combination, the length of the measurement line is obtained from each component by the three-square theorem.

  FIG. 7 shows the calculation principle of the X-axis component CX of the measurement line S including the X-axis component and the Y-axis component. The coordinate values of the end points of the teacher line LTx in the X-axis direction at the two-dimensional coordinates on the image are (xta, yta) and (xtb, ytb), and the two-dimensional coordinates on the images of the end points A and B of the measurement line S are used. Is set to (xa, ya) (xb, yb). Note that the measurement line S in FIG. 7 does not necessarily correspond to the measurement line S in FIG.

  Assuming that the distances from the vanishing point perpendicular lines of the end points A and B of the measurement line S are Sa and Sb, these Sa and Sb can be obtained based on the actual length TL of the teacher line LTx. The X-axis component CX can be obtained as CX = Sa−Sb. Here, the vanishing point perpendicular line is a perpendicular line from the vanishing point V, and in the case of FIG. 7, the x axis is parallel to the teacher line LTx, and thus is a line segment orthogonal to the x axis.

In order to obtain Sa from the actual length TL of the teacher line LTx, the teacher line LTx-a virtually assumed at the position of the coordinate value ya is used. Specifically, when the number of pixels of the teacher line LTx is N, the number of pixels of the teacher line LTx-a is Na, and the number of pixels of Sa is na, Sa is Sa = [(TL / N) · ( TL / Na)] · na. Similarly, Sb can be obtained. The above is the calculation principle of CX. Actually, CX is obtained by the following equation.
CX = | TL ・ {(xa-xv) ・ (yb-ya) / (ya-yv) + xa-xb} ・ (2 ・ yv-yta-ytb) / {2 ・ (xta-xtb) ・ (yv -yb)} |

FIG. 8 shows the calculation principle of the Y-axis component CY of the measurement line S. CY is obtained by projection projection. That is, the y-axis component LTy-v of the teacher line LTy in the Y-axis direction and the y-axis component sv of the measurement line S are parallel to the x-axis by projection on the image along the road from the arbitrarily projected projection center P. Projecting onto a straight line segment, a teacher line projection image LTy-h and a measurement line projection image vs-h are obtained. In this case, the teacher line projection image LTy-h and the measurement line projection image vs-h have the same actual length per pixel. Therefore, the length of CY can be obtained by simply comparing the teacher line projection image LTy-h and the measurement line projection image vs-h with respect to the number of pixels. Specifically, the actual length of the teacher line LTy can be determined as TL, and the length of CY can be determined as CY = TL · vs−h / LTy−h. The above is the calculation principle of CY. Actually, CY is obtained by the following equation.
CY = TL ・ | {(yta-yv) ・ (ytb-yv) ・ (yb-ya)} / {(ya-yv) ・ (yb-yv) ・ (ytb-yta)} |
If CX and CY are obtained as described above, the actual length SL of the measurement line S can be obtained as SL = (CX ² + CY ² ) ^1/2 .

  FIG. 9 shows the calculation principle of the Z-axis component CZ of the measurement line S. In FIG. 9, the measurement line S is parallel to the teacher line LTz in the Z-axis direction. Therefore, the measurement line S consists only of the X-axis component, and CZ = S. The length of CZ can be obtained based on the teacher line LTz on the same principle as the calculation of CX described above. Specifically, the hypothetical teacher line LTz-s is used at the position of the coordinate value yb of the lower end point of the measurement line S, the number of pixels of the teacher line LTz is N, and the number of pixels of the teacher line LTz-s is Na. If the number of pixels of CZ (= S) is na, CZ can be obtained as CZ = [(TL / N) · (TL / Na)] · na.

The above is the calculation principle of CZ. Actually, CZ is obtained by the following equation. However, “ChiHei_Y” in the equation is a coordinate value of the y-axis in the two-dimensional coordinates on the image of the ground plane including the end point B of the measurement line S. This “ChiHei_Y” is the same as the y-axis coordinate value of the end point B when the measurement line S is on the ground plane. However, the end point B of the measurement line S is not necessarily on the ground plane.
CZ = | TL ・ {(yb-ya) ・ (yv-yta) / {(yta-ytb) ・ (yv-ChiHei_Y)} |

  In the measurement using the positional relationship between the vanishing point and the measurement part as described above correlates with the actual length per pixel, the accuracy of the actual length per pixel differs depending on the distance from the camera. If it is too close to or too far from the camera, the accuracy may be insufficient. Therefore, as shown in FIG. 10, it is preferable to appropriately set the measurement region 17 in the roadside image 4 so that the measurement can be performed only in the measurement region 17. In this case, it is appropriate that the teacher line LTx and the teacher line LTz are the outer edges of the measurement region 17. Therefore, the image for generating the teacher line LT is preferably a measurement target image captured under the condition that the teacher line LTx and the teacher line LTz are the outer edges of the measurement region 17.

  Returning to FIG. 4, in step S <b> 6, it is determined whether measurement has been completed for all necessary measurement parts. If this determination is negative, the process returns to step S4 to repeat the process. If the determination is affirmative, the process proceeds to step S7.

  In step S7, the feature data is recorded on the roadside image that has been measured, and image data with feature data is generated. FIG. 11 shows an example of image data with feature data. The feature data-added image data 18 in the example of FIG. 11A is a case where the width data of the road 2 and the height data of the building 19 along the road are recorded, and the example of FIG. The feature data-added image data 20 is a case where the ground height data of the road crossing cable 21 is recorded.

  In step S8, it is determined whether measurement has been completed for all necessary images. If this determination is negative, the process returns to step S1 to repeat the process. If the determination is affirmative, the process ends.

  As mentioned above, although the form for implementing this invention was demonstrated, this is only a representative example and this invention can be implemented with various forms in the range which does not deviate from the meaning. For example, the above example is a case where the reference scale is applied to the measurement of the roadside feature by the roadside image. However, the present invention is not limited to this, and the present invention is applicable to the case of measuring individual buildings. A reference scale is applicable. In addition, the “feature” in “feature measurement” to which the present invention is applied is not limited to a feature according to a general definition, and may be any as long as “feature measurement” can be performed by applying the present invention.

4 image 6 camera 31 reference scale 32 X direction scale 33 Y direction scale 34 Z direction scale 37 scale LT teacher line V vanishing point

Claims (1)

In the image top feature measurement in which the measurement of the feature captured in the image obtained by photographing with the camera is performed based on the vanishing point obtained on the image, the absolute length on the image In the reference scale for measuring the image top feature used to generate the teacher line for which is known for the measurement based on the vanishing point,
X which is combined with each other so as to extend corresponding to the X, Y and Z coordinate axes of the three-dimensional coordinates in the subject space of the image, and each is provided with a scale indicating the known absolute length It has a directional scale, a Y-direction scale, and a Z-direction scale,
The Z-direction scale is composed of a pair of left and right left Z-direction scales and a right-side Z-direction scale positioned so as to sandwich the base end portion of the Y-direction scale from both sides,
The X-direction scale is composed of a left-side X-direction scale extending from the base end of the left-side Z-direction scale and a right-side X-direction scale extending from the base end of the right-side Z-direction scale.
The left Z-direction scale and the left-side X-direction scale, the left-side Z-direction scale and the Y-direction scale, the Y-direction scale and the right-side Z-direction scale, the right-side Z-direction scale and the right-side X-direction scale, respectively. It is combined so that it can be folded around the part,
Each of the directional scales is formed so as to have four side surfaces, and the scale is provided on at least three side surfaces of the four side surfaces . Reference scale.

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