CN108597023A - A kind of geology based on slr camera is appeared 3 D model construction method - Google Patents

Abstract

The invention discloses a method for constructing a three-dimensional model of a geological outcrop based on a single-lens reflex camera. The basic steps are: selecting feature points of the geological outcrop or setting artificial marks as scale marking points; collecting images of the geological outcrop with a camera with a fixed focal length; performing triangulation in the air , automatically extract the connection points, determine the image position through the back calculation of the connection points; add the model scale information; perform aerial triangulation again; build an irregular triangulation network through the connection points, generate a white body model, and add images to it to obtain a 3D geological outcrop Model; optimize the model, fill in the holes in the model and crop the uninteresting areas to achieve model optimization. The method provided by the invention has the advantages of being scientific and reasonable, easy to implement, and high in precision. A single-lens reflex camera is used to collect images of the geological outcrop to construct a three-dimensional model of the geological outcrop.

Description

A 3D Model Construction Method of Geological Outcrop Based on SLR Camera

technical field

The invention relates to the technical field of three-dimensional visualized geological modeling, in particular to the application field of building a three-dimensional model of a geological outcrop, in particular to a method for collecting geological outcrop images by a single-lens reflex camera and using the image data to construct a three-dimensional model of the geological outcrop.

Background technique

Geological outcrops are geological bodies exposed on the earth's surface. Studying the characteristics of geological outcrops is an important means to understand the geological conditions of underground reservoirs. As the goals of geological research tend to be more refined and complex, and the scale of geological body representation is getting smaller and smaller, the traditional method of geological outcrop investigation (taking photos with geological hammers and benchmarks as reference objects) is used to obtain geological body parameters It has been difficult to meet the development needs.

The 3D modeling technology of geological bodies has been applied in the field of geological engineering. The 3D model of geological outcrops uses digital means to collect spatial information, color information and texture information of geological outcrops, and truly restores the field scene of geological outcrops. Through this model, refined 3D spatial analysis and repeated research on the characteristics of geological outcrops can be realized. The current 3D modeling method for geological outcrops mainly uses 3D laser scanners to collect point cloud information (that is, spatial information) of geological outcrops, combined with SLR cameras to collect image data, and obtains 3D models of geological outcrops through fusion modeling of the two, but 3D laser scanning The instrument is expensive and complicated to operate, and has not been widely used in geological surveys.

In order to explore a low-cost and easy-to-operate 3D modeling method for geological outcrops, the present invention uses photogrammetry technology to invent a set of 3D model building methods for geological outcrops based on SLR camera image data. description and high-precision measurement.

Contents of the invention

(1) Technical problems to be solved

The invention provides a method for constructing a three-dimensional model of a geological outcrop based on a single-lens reflex camera, which fully considers the characteristics of the geological outcrop and the needs of geological investigations, and can realize the refinement of the geological outcrop by carrying out geological three-dimensional outcrop modeling and restoring the scene of the geological outcrop Measure and describe.

(2) Technical solution

The present invention comprises the following steps:

(1) Set the scale mark point

Select geological outcrop feature points or set artificial markers as scale marking points, and their size should be greater than the minimum spatial resolution of the image to be collected to ensure that they can be clearly distinguished on the image. Set the scale marking points of the three specific conditions as A, B, and C, and use a steel ruler to accurately measure the distance between the scale marking points (in meters), and take the position to the whole millimeter.

(2) Image acquisition

Geological outcrop images are collected with a camera with a fixed focal length. During this process, the distance between the camera and the geological outcrop should be kept as consistent as possible, and the overlap rate between each image should be kept greater than 75%. According to the front, left, right, upper and lower sides Collect images of geological outcrops in a specific sequence to ensure clear images and full coverage of the outcrop area.

(3) The first aerial triangulation and image selection

Carry out aerial triangulation, automatically extract connection points, and determine the image position through back calculation of connection points. According to the calculation results of aerial triangulation, if the unmatched image is located in the area with uniform connection point density, the unmatched image is directly eliminated; if the unmatched image is located in the area with uneven connection point density, the unmatched image and its adjacent images are artificially Add a specific number of connection points.

(4) Add model scale information

Find and select the scale identification points A, B, and C set in step (1) on the image as the scale constraint points, which are a, b, and c in turn, and set the distance between the constraint points.

(5) Secondary aerial triangulation

Repeat the operation of step (3) until the aerial triangulation is qualified.

(6) 3D model establishment

Through the connection points generated in step (5), construct an irregular triangular network and a white body model, and fit the texture to the white body model to obtain a 3D model of the geological outcrop with images that are not blocked by debris and have a uniform posture and no misalignment. .

(7) 3D model optimization

On the basis of step (6), the model is optimized, including model hole filling and uninteresting area clipping. To fill the hole, you need to select appropriate parameters to fill the white body model, and then fit the texture.

Further, the scale marking points A, B, and C in the step (1) should be in the shape of an isosceles right triangle as much as possible, and the setting distance of the waist lengths AB and AC is between 0.5m and 1m.

Further, in the step (3), a certain number of connection points are respectively located in the four corners and 5 points in the center in the overlapping area on the adjacent images.

Further, the scale identification points A, B, and C in the step (1) are respectively pricked in the corresponding image to obtain a, b, and c in the step (4), and when setting the distance between the constraint points, the length of ab Set as the measurement distance of the waist length AB, and set the ac length as the measurement distance of the waist length AC.

Further, the principle of parameter selection in step (7) is to use plane filling for holes within the area of S (0≤S≤0.1) square meters, and to use curved surface filling for holes within the area of S (0.1<S≤0.5) square meters , for holes within the area of S (S>0.5) square meters, use a curve to build a bridge in the middle of the hole, and then fill it with a curved surface.

(3) Beneficial effects (advantages)

The advantages of the present invention are reflected in:

Due to the limitations of 3D laser scanners such as high price, poor portability and inconvenient field operation, it is difficult to use 3D laser scanners for 3D modeling of geological outcrops. From the viewpoints of applicability and usability, the invention uses a single-lens reflex camera to collect images of geological outcrops to generate three-dimensional geological outcrops with scale information. On the basis of restoring the scene of geological outcrops in the field, the measurement work that originally required field investigations can be described quantitatively and finely on the computer, which is of great significance for the accurate description of geological outcrops.

Description of drawings

Fig. 1 is the flow chart of the steps that the present invention implements,

Fig. 2 is a schematic diagram of the distribution of scale identification points provided by the implementation of the present invention,

Fig. 3 is the calculation result figure of aerial triangulation provided by the implementation of the present invention,

Fig. 4 is a schematic diagram of the location distribution of selected connection points in the adjacent image overlapping area provided by the implementation of the present invention,

Fig. 5 is the irregular triangular network diagram of the geological outcrop provided by the implementation of the present invention,

Fig. 6 is a three-dimensional model diagram of a geological outcrop white body provided by the implementation of the present invention,

Fig. 7 is a three-dimensional model diagram of a geological outcrop provided by the implementation of the present invention.

Detailed ways

In order to make the purpose, content, and advantages of the present invention clearer, the specific implementation of the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments:

With reference to Fig. 1, concrete implementation steps of the present invention are:

(1) Set the scale mark point

Select geological outcrop feature points or set artificial markers as scale marking points, and their size should be greater than the minimum spatial resolution of the image to be collected to ensure that they can be clearly distinguished on the image. Set the scale marking points of the three specific conditions as A, B, and C, and use a steel ruler to accurately measure the distance between the marking points (in meters), and take the position to the full millimeter.

The scale marking points A, B, and C are in the shape of an isosceles right-angled triangle as much as possible (refer to FIG. 2 ), and the setting distance range of the waist lengths AB and AC is between 0.5 m and 1 m.

(2) Image acquisition

Geological outcrop images are collected with a camera with a fixed focal length. During this process, the distance between the camera and the geological outcrop should be kept as consistent as possible, and the overlap rate between each image should be kept greater than 75%. According to the front, left, right, upper and lower sides Collect images of geological outcrops in a specific sequence to ensure clear images and full coverage of the outcrop area.

(3) The first aerial triangulation and image selection

Carry out aerial triangulation, automatically extract connection points, and determine the image position through back calculation of connection points. According to the calculation results of aerial triangulation (refer to Figure 3), if the unmatched image is located in the area with uniform connection point density, the unmatched image is directly eliminated; if the unmatched image is located in the area with uneven connection point density, the unmatched image and other A specific number of tie points are artificially added to adjacent images.

A certain number of connection points are respectively located at the four corners and the center of five points in the overlapping area on adjacent images (refer to FIG. 4 ).

(4) Add model scale information

Find and select the scale identification points A, B, and C set in step (1) on the image as the scale constraint points, which are a, b, and c in turn, and set the distance between the constraint points.

Among them, the scale identification points A, B, and C in step (1) are respectively pricked in the corresponding image to obtain a, b, and c in step (4). When setting the distance between the constraint points, set the length of ab to waist The measurement distance of length AB, set the length of ac to the measurement distance of waist length AC.

(5) Secondary aerial triangulation

Repeat the operation of step (3) until the aerial triangulation is qualified.

(6) 3D model establishment

Through the connection points generated in step (5), construct an irregular triangular network (refer to Figure 5) and a white body model (refer to Figure 6), and use image bonding with no sundries, uniform posture and no misalignment for the bonding texture A three-dimensional model of the geological outcrop is obtained on the white body model (refer to Fig. 7).

(7) 3D model optimization

On the basis of step (6), the model is optimized, including model hole filling and uninteresting area clipping. To fill the hole, you need to select appropriate parameters to fill the white body model, and then fit the texture.

The principle of parameter selection is to use plane filling for holes within the area of S (0≤S≤0.1) square meters, for holes within the area of S (0.1<S≤0.5) square meters to fill with curved surfaces, and for areas of S (S >0.5) For holes within the square meter range, use curves to build bridges in the middle of the holes, and then fill them with curved surfaces.

Claims (5)

1. The 3 D model construction method 1. a kind of geology based on slr camera is appeared, which is characterized in that include the following steps：

   (1) scale identification point is set

   Select geology appear characteristic point or setting artificial target as scale identification point, size should be greater than image to be collected most Low spatial resolution ensures clearly differentiate on image, and the scale identification point of 3 specified conditions of setting is A, B, C, utilizes steel The distance between ruler accurate measuring scale identification point (unit is rice), fetch bit to whole millimeter；

   (2) image collection

   Geology image of appearing is acquired using the camera of fixed focal length, should during the distance appeared of camera distance geology as possible It is consistent, Duplication is remained above 75% between every image, by the particular order in front, left side, right side, the upper side and lower side The image that acquisition geology is appeared ensures image definition and region all standing of appearing；

   (3) aerial triangulation for the first time is chosen with image

   Aerial triangulation is carried out, tie point is automatically extracted, image position is determined by tie point inverse；It is surveyed according to aerial triangle If amount calculates as a result, not matching image is located at tie point even density region, directly rejects this and do not match image；If not matching Image is located at tie point Density inhomogeneity region, then manually adds certain amount of company on not matching image image adjacent with its Contact；

   (4) model dimension information is added

   It is searched on image and scale identification point A, B, C of selecting step (1) setting is followed successively by a, b, c as dimensional constraints point, The distance between and obligatory point is set；

   (5) secondary aerial triangulation

   The operation of step (3) is repeated, until aerial triangulation is qualified；

   (6) three-dimension modeling

   By the tie point generated in step (5), irregular triangle network and lean type model are built, fitting texture selects no-sundries to hide Gear, posture uniformity dislocation-free image be fitted on lean type model and obtain geology and appear threedimensional model；

   (7) threedimensional model optimizes

   Model is optimized on the basis of step (6), including area's cutting is filled up and lost interest in models holes；Fill up hole Suitable parameters dialogue body Model need to first be chosen to be filled up, be then bonded texture again.
2. The 3 D model construction method 2. a kind of geology based on slr camera according to claim 1 is appeared, feature exist In：Described step (1) mesoscale identification point A, B, C are in isosceles right triangle, the setting distance range of waist long AB and AC as possible Between 0.5 meter to 1 meter.
3. The 3 D model construction method 3. a kind of geology based on slr camera according to claim 1 is appeared, feature exist In：Certain amount of tie point is located at four corners, centers in the step (3) in the overlapping region on adjacent image Totally 5 points.
4. The 3 D model construction method 4. a kind of geology based on slr camera according to claim 1 is appeared, feature exist In：A, b, c during by scale identification point A, B, C in step (1), thorn point obtains step (4) in corresponding image respectively, setting When the distance between obligatory point, sets ab length to the measurement distance of the long AB of waist, set ac length to the measurement of the long AC of waist Distance.
5. The 3 D model construction method 5. a kind of geology based on slr camera according to claim 1 is appeared, feature exist In：Parameter selection rules are to use plane for the hole within the scope of area S (0≤S≤0.1) square metres in the step (7) It fills up, for area S (0.1<S≤0.5) square metre within the scope of hole filled up using curved surface, for area S (S>Square 0.5) Hole in rice range is first put up a bridge among hole with curve, then is filled up with curved surface.