CN111854699A - A monitoring method for river bank collapse process based on UAV aerial survey - Google Patents

Abstract

The invention discloses a monitoring method based on unmanned aerial vehicle (UAV) aerial survey of river bank collapse process, which belongs to the field of terrain data processing. According to the requirements, determine the flight height and overlap of UAV, and obtain aerial survey image data; use RTK carrier phase difference technology to correct terrain data; use image processing tools to perform DEM noise reduction processing to obtain high-precision, high-resolution terrain data. The longitudinal crack length a, width b, bank slope width c and bank slope height h of the collapsed bank in the river reach are calculated to calculate the critical equilibrium soil volume and critical slope; through multiple aerial survey data, ArcMap is used to calculate the collapsed river reach. Topographic changes, and then calculate the annual bank collapse volume at the river reach scale. The invention can save manpower and simplify the work flow, and monitor the river bank collapse process efficiently.

Description

A monitoring method for river bank collapse process based on UAV aerial survey

technical field

The invention belongs to the field of terrain data processing, and relates to interdisciplinary subjects such as river bed evolution, sediment movement mechanics, and application of unmanned aerial vehicle aerial survey technology, and more particularly, to a monitoring method based on unmanned aerial vehicle aerial survey of river bank collapse process.

Background technique

The bank collapse is the direct result of the scouring of the river bank by the impulsive water flow of the river channel. Peristalsis has an important effect. There are various types of bank collapse, which can be divided into wash collapse, strip collapse and nest collapse according to the plane form. According to the mechanical mode, it can be divided into shallow collapse, plane sliding, arc sliding and cantilever collapse. The rapid widening of the river bank and the transport of a large amount of sediment caused by the collapse of the bank can greatly change the water and sediment transport conditions in the local river reach in a short time, thus having a severe impact on the evolution of the river bed.

Existing bank collapse monitoring mainly obtains relevant bank collapse information (such as river bank height, slope and scouring range of slope foot, etc.) through the observation of water, sediment and topographic data before and after flood season; Electronic instruments such as GNSS, single-beam bathymetry systems, and multi-beam bathymetry systems are used to measure underwater and onshore topography; and based on remote sensing images to extract and monitor the information of the topography of the river reach, reflecting the changing process of the shoreline. In addition, the measurement of the flow, sediment content and water level changes of each hydrological and water level section along the route can be used to analyze and study the water level fluctuation and flood peak process of the river section in real time. By manipulating the sailing ADCP in the field, the local water flow conditions of the bank collapse section can be obtained. With the development and application of technologies such as automatic monitoring equipment, network information communication, and computers, GNSS, multi-point displacement gauges, land displacement gauges, and land pressure gauges have been used in a targeted manner to realize real-time monitoring, collect and transmit insurance data. Data such as riverbed deformation and riverbed boundary changes in the near-shore section of the section were used to analyze the development trend of the riverbank in the dangerous section. However, due to the limitation of field conditions, the installation, maintenance and arrangement of detection points of these detection equipment are quite difficult, so the application in actual shore collapse observation and monitoring is relatively rare at this stage.

The current technical means and measurement methods require a lot of manpower and carry heavy tools, the operation is cumbersome and the precision is not high, and the manual operation will bring unavoidable errors.

SUMMARY OF THE INVENTION

Aiming at the above defects or improvement needs of the prior art, the present invention proposes a monitoring method based on UAV aerial survey of river bank collapse process, which is simple to operate, has less interference, and can greatly reduce time and labor costs.

In order to achieve the above object, according to one aspect of the present invention, a method for monitoring the river bank collapse process based on the aerial survey of the unmanned aerial vehicle is provided, comprising:

(1) Arrange the RTK points in an orderly manner, determine the flight height and overlap of the UAV by the bank slope width c and bank slope height h of the parameter sample, and obtain the UAV aerial survey data;

(2) using image data processing software to process the aerial survey data of the UAV;

(3) Obtain the longitudinal crack length a, longitudinal crack width b, bank slope width c and bank slope height h of the bank that is about to collapse in the river reach through the processed UAV aerial survey data, and calculate the critical equilibrium soil volume and critical balance. slope;

(4) Using the ArcMap software to calculate the terrain difference DoD through the aerial survey data of multiple UAVs.

Preferably, step (1) includes:

The average value of the measured bank slope width c and bank slope height h is used as the basis for the flight height and overlap of the UAV, the longitudinal crack width b of the concave bank is used as the limit value of the geometric minimum resolution of the UAV, and the bank slope height h As the limit value of the elevation data resolution after UAV image data processing.

Preferably, step (2) includes:

Use image data processing software to classify and extract the aerial survey data of the UAV, calculate 3D orthophotos and perform deep noise reduction processing, wherein the image data processing software includes one or more of Pix4D, Cloud Compare and ArcGIS combination.

Preferably, step (3) includes:

Using the processed UAV aerial survey data and the precise positioning of RTK, calculate the three-dimensional terrain within the river bank, and use the image processing tool of ArcMap to perform in-depth processing of DEM noise on the three-dimensional terrain to obtain the parameters required for bank collapse monitoring. The crack length a, the longitudinal crack width b of the concave bank, the bank slope width c and the bank slope height h, the bank parameter data and terrain data obtained by UAV aerial surveys are used to identify the critical state of bank collapse, and the critical equilibrium soil volume and critical slope are calculated. .

Preferably, the critical equilibrium soil volume is calculated from V=a×c×h/3, and the critical slope is calculated from β=ctan(h/c).

Preferably, step (4) includes:

Based on the deep denoised topographic data obtained by repeated aerial surveys before and after the flood season, the topographic difference DoD was generated by using the image processing tool of ArcMap, and the annual bank collapse volume at the river reach scale was calculated.

Preferably, in step (1), the orderly arrangement of RTK points includes:

Determine the boundaries on the upstream and downstream sections of the river reach, find the highest and lowest points of the river reach, and arrange RTK points for the determined boundary, highest and lowest points of the river reach, and click the terrain inflection point for the complicated terrain in the river reach. Supplement RTK points.

According to another aspect of the present invention, there is provided a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, implements the steps of any one of the above-mentioned methods.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The geometric resolution of aerial survey obtained by unmanned aerial vehicle can reach centimeter level, which can clearly identify the general river bank shape and its longitudinal cracks;

(2) The terrain data of different periods can be obtained quickly and accurately, and the terrain difference DoD generated by processing has high reliability;

(3) The calculation of critical equilibrium soil volume and critical slope is simple;

(4) The numbering method of RTK points is simple and can be quickly identified, the cost of materials used is low, and it is easy to obtain;

(5) The workload required for the entire field investigation and observation is small, and only three surveyors at most can complete the aerial survey task of the river section A.

(6) The present invention can save manpower and improve efficiency, obtain high-precision river bank parameters and topographic data, generate topographic difference DoD, and calculate the annual bank collapse volume of the river section scale, thereby realizing the monitoring of the bank collapse process.

Description of drawings

1 is a schematic flowchart of a monitoring method for a river bank collapse process based on aerial survey of a river channel provided by an embodiment of the present invention;

Fig. 2 is a kind of RTK dotting schematic diagram provided by the embodiment of the present invention;

Fig. 3 is a kind of drone aerial survey river bank profile schematic diagram provided by the embodiment of the present invention;

Fig. 4 is a kind of drone aerial survey river bank overlooking schematic diagram provided by the embodiment of the present invention;

Among them, 1- lime powder fixed point, 2- concave bank slope, 3- longitudinal fissure, 4- drone, 5- pan/tilt, 6- camera.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Unmanned Aerial Vehicle (UAV) technology has developed rapidly in recent years. UAV aerial survey has the advantages of simple operation, high data quality and cost saving. field measurement method. Combined with the noise processing technology based on the aerial survey terrain data of the unmanned aerial vehicle, the present invention proposes a monitoring method for the river bank collapse process based on the aerial survey of the unmanned aerial vehicle. DEM of Difference). The method is simple to operate, has less interference, and can greatly reduce the time and labor costs. While obtaining the river bank parameters and topography, the topographic difference DoD is generated, and the annual bank collapse volume at the river reach scale is calculated to monitor the river bank collapse process.

The invention is mainly aimed at the acquisition of river bank parameters and terrain data in the river reach, and the tools used include ruler, lime powder, unmanned aerial vehicle and RTK (Real-time kinematic). As shown in Figure 1, it includes the following steps:

S1: Arrange the RTK points in an orderly manner, determine the flight height and overlap of the UAV by the bank slope width c and bank slope height h of the parameter sample, and obtain the aerial survey data of the UAV;

As a preferred embodiment, step S1 can be implemented in the following ways:

The average value of the measured bank slope width c and bank slope height h is used as the basis for the flight height and overlap of the UAV, the longitudinal crack width b of the concave bank is used as the limit value of the minimum geometric resolution of the UAV, and the bank slope height h is used as the limit value of the geometric minimum resolution of the UAV. The limit value of the elevation data resolution after UAV image data processing.

Specifically, first determine the river section where the bank will collapse (hereinafter referred to as the river section A) that needs to be studied and measured, confirm the boundary of the river section A, determine the boundary between the upstream section and the downstream section of the river section A, and sprinkle lime on the boundary. Fan 1 uses a fixed point to determine several points on the boundary (the first 4 points in the sequence number in Figure 2), and find the highest point, the lowest point, and the complex terrain point (usually terrain) of the river section A in turn in the direction of the river flow. The inflection point of the height difference change) and the terrain inflection point, continue to sprinkle lime powder on these points to fix the points (the last two points in the sequence number in Figure 2), and number them in sequence; then arrange RTK points for the points that have been numbered with lime powder bit, as shown in Figure 2.

Among them, the lime powder number is used because the lime powder fixed point can be clearly identified in the image generated when the drone conducts orthophoto aerial photography.

Further, since imaging in three-dimensional space requires the values of three coordinates of XYZ (longitude (X), dimension (Y) and height (Z)), the selected river segment is sampled, and along the direction of the river bed flow, every Several meters (such as 5m) are randomly selected for a section of the river bank sample. As shown in Figure 3 and Figure 4, by randomly measuring the width c and the bank slope height h of several (such as 10) concave bank slopes 2, the average value of the bank slope width c and the bank slope height h is calculated and used as The basis for the flight height and overlap of UAV 4. The width b of the longitudinal crack 3 of the concave bank is used as the limit value of the geometric minimum resolution of UAV, and the bank slope height h is used as the limit value of the resolution of the elevation data after UAV image data processing. At present, the minimum safe flight height of civil drones is 20m, and the maximum is more than 200m. The geometric resolution of aerial survey corresponding to this flight height range fully meets the monitoring of bank collapse of different rivers, and can clearly identify longitudinal cracks with a minimum width of 5cm.

Then, perform a test flight on the grouping of heights and overlapping degrees within the range, and drive the camera 6 to shoot through the gimbal 5; under the condition that the flight attitude of the UAV satisfies the errors of the roll angle, heading angle and pitch angle within ±3° , Using Pix4Dmapper software, according to RTK positioning data, image data and attitude data, to evaluate the quality of UAV images. Eliminate images that do not meet the mapping specification, generate a quality report, and finally determine the final flight height and overlap by the quality report.

Among them, when the flying height of the drone and the overlap of the image are determined, the drone route of the river A can also be confirmed.

Use image data processing software such as Pix4D, Cloud Compare and ArcGIS to simulate aerial triangulation and establish flight zones. A single model is established by calculating the relative orientation elements and the coordinates of the model points, and the model connection operation is performed by using the common connection points between adjacent models to establish a three-dimensional model of the airway with a unified scale. Each airway model unit should be roughly leveled and unified in a common coordinate system, and finally the overall adjustment operation should be performed. To this end, it is necessary to list the respective nonlinear correction formulas for each flight zone, and calculate the unified adjustment according to the least squares method to obtain the nonlinear correction parameters of each flight zone. In the calculation process, it is necessary to consider that the ground coordinates of the connection points of the same name between adjacent air strips are equal, and the internal coordinates of the control points are equal to the measured coordinates of the field, and the sum of the squares of the corrections of the coordinates of each model point must be minimized, so as to obtain the final result. The ground coordinates of the encryption point of the whole area network. The flight zone determined by the ground coordinates is the UAV route.

S2: Use image data processing software to process UAV aerial survey data;

As a preferred embodiment, step S2 can be implemented in the following ways:

Use image data processing software including Pix4D, Cloud Compare, ArcGIS to classify and extract UAV aerial survey data, calculate 3D orthophoto images, and process deep noise reduction.

Further, the UAV aerial survey data is processed: the UAV orthophoto map (Digital OrthophotoMap, DOM) is the result obtained after the UAV completes the flight mission, and then the UAV aerial survey image photos are used to calculate pixel by pixel. The sequence of preprocessing, geometric correction and mosaicking is performed, and an image set is formed by cropping in a certain scale range. This image set contains the sand wave morphological parameter information to be measured. Using image filtering processing, lens distortion correction, geometric correction, relative orientation, absolute orientation, aerial triangulation, and image registration and coordination to achieve rapid image stitching.

S3: Obtain the longitudinal crack length a, width b, bank slope width c and bank slope height h of the bank that is about to collapse in the river reach through the processed UAV aerial survey data, and calculate the critical equilibrium soil volume and critical slope;

As a preferred embodiment, step S3 can be implemented in the following ways:

Using the processed UAV high-precision orthophoto set and RTK accurate positioning, calculate the three-dimensional terrain within the river bank, and use the image processing tool of ArcMap to perform DEM noise depth processing on the three-dimensional terrain to obtain the parameters required for bank collapse monitoring. The longitudinal crack length a, the longitudinal crack width b of the concave bank, the bank slope width c and the bank slope height h, the bank parameter data and terrain data obtained by UAV aerial surveys are used to identify the critical state of bank collapse, and the cross section of the critical soil is a triangle. , the soil volume formula for calculating the critical equilibrium is V=a×c×h/3, and the critical slope β=ctan(h/c).

Specifically, using Pix4D and Cloud Compare, according to certain parameter settings, considering the precise positioning of RTK, the orthophoto image set is calculated. Use ArcMap's image processing tools to perform in-depth processing of DEM noise, obtain high-resolution and high-precision river bank DEM data of Reach A through noise reduction, and then obtain the length a, width b, and bank slope width of longitudinal cracks on the concave bank of Reach A. c and bank slope height h.

Further, according to the length a, width b, bank slope width c and bank slope height h of the longitudinal cracks of the concave bank of the river reach A obtained by the drone, the critical state of the bank collapse is identified, and the critical equilibrium soil volume and the critical balance are calculated. slope.

S4: Calculate the terrain difference DoD by using ArcMap software through multiple aerial survey data of UAV.

As a preferred embodiment, step S4 can be implemented in the following ways:

Based on the deep noise-reduced terrain data obtained by repeated aerial surveys before and after the flood season, the image processing tool of ArcMap is used to generate the topographic difference DoD, and the annual bank collapse volume at the river reach scale (such as within 3km) is calculated.

The present invention obtains river bank slope parameters through aerial survey by unmanned aerial vehicle, and calculates the critical equilibrium soil volume and critical slope. Through repeated aerial surveys before and after the flood season by drones, the DEM topographic variation is generated, which is the annual bank collapse volume at the river reach scale.

It should be pointed out that, according to the needs of implementation, the various steps/components described in this application may be split into more steps/components, or two or more steps/components or partial operations of steps/components may be combined into new steps/components to achieve the purpose of the present invention.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (8)

1. a monitoring method based on unmanned aerial vehicle aerial survey river bank collapse process, is characterized in that, comprises: (1) Arrange the RTK points in an orderly manner, determine the flight height and overlap of the UAV by the bank slope width c and bank slope height h of the parameter sample, and obtain the UAV aerial survey data; (2) using image data processing software to process the aerial survey data of the UAV; (3) Obtain the longitudinal crack length a, longitudinal crack width b, bank slope width c and bank slope height h of the bank that is about to collapse in the river reach through the processed UAV aerial survey data, and calculate the critical equilibrium soil volume and critical balance. slope; (4) Using the ArcMap software to calculate the terrain difference DoD through the aerial survey data of multiple UAVs. 2. The method according to claim 1, wherein step (1) comprises: The average value of the measured bank slope width c and bank slope height h is used as the basis for the flight height and overlap of the UAV, the longitudinal crack width b of the concave bank is used as the limit value of the geometric minimum resolution of the UAV, and the bank slope height h As the limit value of the elevation data resolution after UAV image data processing. 3. The method according to claim 1, wherein step (2) comprises: Use image data processing software to classify and extract the aerial survey data of the UAV, calculate 3D orthophotos and perform deep noise reduction processing, wherein the image data processing software includes one or more of Pix4D, Cloud Compare and ArcGIS combination. 4. The method according to any one of claims 1 to 3, wherein step (3) comprises: Using the processed UAV aerial survey data and the precise positioning of RTK, calculate the three-dimensional terrain within the river bank, and use the image processing tool of ArcMap to perform in-depth processing of DEM noise on the three-dimensional terrain to obtain the parameters required for bank collapse monitoring. The crack length a, the longitudinal crack width b of the concave bank, the bank slope width c and the bank slope height h, the bank parameter data and terrain data obtained by UAV aerial surveys are used to identify the critical state of bank collapse, and the critical equilibrium soil volume and critical slope are calculated. . 5 . The method according to claim 4 , wherein the critical equilibrium soil volume is calculated from V=a×c×h/3, and the critical slope is calculated from β=ctan(h/c). 6 . 6. The method according to claim 5, wherein step (4) comprises: Based on the deep denoised topographic data obtained by repeated aerial surveys before and after the flood season, the topographic difference DoD was generated by using the image processing tool of ArcMap, and the annual bank collapse volume at the river reach scale was calculated. 7. The method according to claim 4, wherein in step (1), the orderly arranging RTK points comprises: Determine the boundaries on the upstream and downstream sections of the river reach, find the highest and lowest points of the river reach, and arrange RTK points for the determined boundary, highest and lowest points of the river reach, and click the terrain inflection point for the complicated terrain in the river reach. Supplement RTK points. 8. A computer-readable storage medium on which a computer program is stored, characterized in that, when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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