CN117671130A - Digital twin intelligent fishing port construction and use method based on oblique photography - Google Patents

Abstract

The invention relates to a digital twin intelligent fishing port construction and use method based on oblique photography, which belongs to the field of geographic information and comprises the following steps: (1) digital twin scene construction is carried out; (2) video fusion of fishing ports; (3) management of twin berths of the fishing port; 4) And (5) port area target radar tracking. The invention takes a three-dimensional live-action model produced by oblique photography as a main mode and a fine model produced by fine modeling as an auxiliary mode, combines and builds a high-efficiency and realistic digital twin fishing port scene, adopts an open source WebGIS (network geographic information system) frame such as Cesium or Maptalks and the like at the front end to conduct high-performance rendering and displaying on the twin scene, and completes the twin functions such as video fusion, berth management, radar tracking and the like by matching with mature internet technologies such as software and hardware equipment and IOT and the like.

Description

Construction and use of digital twin smart fishing port based on oblique photography

Technical field

The invention relates to a method of building and using a digital twin smart fishing port based on oblique photography, and belongs to the field of geographical information.

Background technique

Digital twins are virtual scenes constructed after digitizing real scenes using new technologies such as physical models, Internet of Things technology, big data analysis, and virtual simulation. Virtual and real world data and operations are interoperable. Digital twin technology allows users to remotely interact with each other through the virtual world. Understand the status of entities remotely and perform operations with feedback. Compared with the two-dimensional flat world, the visual experience of the twin scene is more intuitive, which can effectively improve the user's target management efficiency in the twin scene and simplify maintenance work. As demand increases, smart fishing ports have emerged. Although the visualization of the port area has been initially achieved, there are a series of problems such as unrealistic display effects and few virtual and real interactive functions. Oblique photogrammetry is to carry multiple sensors on a flying platform to collect ground image data from multiple angles at the same time. After data processing, it can obtain accurate and complete position information and texture data of ground objects, and produce a three-dimensional real-life model with realistic effects and high spatial accuracy. .

In terms of digital twin fishing ports, the Xiangshan County Big Data Development Center mainly uses technologies such as dynamic sensing, digital twins, algorithm identification, data analysis, mechanism reshaping and digital transformation empowerment to create digital twin fishing ports to solve the "invisible" problem of fishery safety governance. There are a series of problems such as "cannot distinguish" and "poor management", but the system is at the virtual simulation level. Wang Shuo, Xuanying Ying and others applied 3D real-life modeling technology to the power grid digital twin system, confirming that the 3D real-life model can enrich the display layer of the digital twin power grid and provide various sensor equipment, power infrastructure, etc. with placeable, displayable, and Measurable basic layers effectively improve the construction and display effects of digital twin scenes. In terms of oblique photogrammetry, with the development of drone technology, the implementation threshold has been gradually lowered and work efficiency has been significantly improved. As a small multi-rotor high-precision aerial survey drone, the Phantom 4 RTK is designed for low-altitude photogrammetry applications and has centimeter-level navigation. The positioning system and high-performance imaging system are portable and easy to use, with high aerial survey efficiency. It also provides two oblique photography flight route planning solutions: tic-tac-toe flight and five-way flight. It can not only produce three-dimensional real-life models, but also provide centimeter-level high-resolution DOM (orthophoto) and DSM (digital surface model) to achieve high-precision and low-cost modeling of fishing ports.

At present, the difficulties of browser-side digital twin technology are mainly reflected in two aspects: 1. Scene construction, especially the construction of twin scenes. The real scene area is usually larger. How to build a scene close to the real environment at low cost and quickly is the key to digital twins. The focus of project development; 2. Scene rendering. There are currently two major rendering solutions. One is rendering through the WebGL (3D drawing protocol) framework, such as Three.js, cesium and other open source frameworks. The advantage of this solution is that it can be developed and used The cost is low, but there is a lag problem when loading complex scenes; the other type is developed through game engines and performs cloud rendering in the form of pixel streams. Although this solution can achieve high-performance front-end rendering, the cost of use is much higher than WebGL. . How to balance cost and experience effect is an accompanying issue of digital twin smart fishing port. Therefore, a digital twin smart fishing port system based on oblique photography is proposed.

Contents of the invention

In order to overcome the shortcomings of the existing technology, the present invention provides a method for building and using a digital twin smart fishing port based on oblique photography. The technical solution of the present invention is:

A method of building and using a digital twin smart fishing port based on oblique photography, including:

(1) Digital twin scene construction; (2) Fishing port video fusion;

(3) Fishing port twin berth management; 4) Port target radar tracking.

Described step (1) specifically includes:

(1-1) UAV aerial photography: After conducting an oblique photography flight survey on the fishing port area, the aerial photography area covering the fishing port is drawn using markup language; in order to ensure the accuracy of the oblique photogrammetry results, the selection of image control points should be evenly distributed in the port area; after marking the image control points by ground spraying or selecting landmark features, use RTK equipment to measure the image control points;

That is: check the fishing port environment before flying to determine whether the current environmental conditions meet the requirements for flight. If the conditions are met, assemble the drone. When the drone self-test is correct and the RTK module is used normally, aerial photography can be started;

(1-2) Fishing port modeling: Export the raw data captured from the drone, and use ContextCapture software to sequentially perform raw data reading, first aerial triangulation, punctuation, second aerial triangulation and modeling. , and generate original three-dimensional reality model data in OSGB and OBJ formats, where the first aerial triangulation is used to calculate the outer azimuth elements of each photo; the second aerial triangulation is used to improve the outer azimuth angle of the photo Calculation accuracy of elements, corrected models;

(1-3) Fishing port model repair: Use ModelFun software to optimize the original 3D real-life model, import the OSGB and OBJ format data set model, and regenerate the OSGB data after the model repair is completed;

(1-4) Refined modeling of the fishing port: Based on the modeling situation of the original three-dimensional real-life model, determine the areas in the port area that require refined modeling, use modeling software to conduct refined modeling, and generate the OBJ model after the modeling is completed. ;

(1-5) Fishing port model rendering: Convert the repaired results into 3D Tiles format; use Cesium or MapTalks open source GIS framework to load 3D Tiles data on the browser side, adjust parameters based on project requirements, and realize front-end rendering of three-dimensional real-life scenes.

The specific steps (2) are:

(2-1) Carry out detailed modeling of the camera in the twin scene and load it to the corresponding location in the scene. At the same time, add a response event to it to control the opening or closing of the camera; when the event response is enabled, use the Cesium camera to create a view frustum to Simulate the visual range of the surveillance camera, and automatically switch the perspective of the twin scene to the corresponding position on the surveillance screen based on the camera position, azimuth angle and focal length parameters provided by the back-end interface;

(2-2) Adjust the camera's view cone so that the view cone correctly reflects the real camera focal length, angle and position; use Cesium's ShadowMap function to analyze the visual domain of the camera's view cone range;

(2-3) Create a video tag and generate a video texture by playing the video stream; use GLSL language to write texture processing logic, and the visible area within the view frustum calculates the relative coordinates and shadow coordinates of the camera through the video texture and corresponding vertices. To obtain the corresponding gl_FragColor, the shadow area retains the original texture of the model;

(2-3) In order to avoid video deformation caused by projection from affecting the visual experience, an additional set of video components is created to synchronously display the normal playback screen, and the video player is bound to the camera position in the twin scene through the callback function provided by Cesium. .

The specific steps (3) are:

(3-1) Carry out intelligent twin management of berths in the port and provide a berth reservation function. Fishermen can view the map-based regional division and usage status of the berths in real time through the WeChat applet, and select vacant berths for online reservation and intelligent path planning;

(3-2) Display the current usage status of berths in the port in the form of a two-dimensional map combined with vector elements in the mini applet; select an idle berth to make a reservation, and after receiving the reservation command in the background, push the reservation information to the twin scene through websocket. The scene uses gradient walls of different colors to display the real-time status of the berth; click on the berth to display the recent usage statistics of the berth; in the background, the coordinates and orientation information of the fishing vessel are obtained in real time through the positioning equipment installed on the fishing vessel, combined with the near-port radar or monitoring screen, twin The scene performs route planning for fishing boat berthing based on the transmission information;

(3-3) Use the A* algorithm to provide necessary berth route planning for fishing boats. First, perform data preprocessing, vectorize the berths through remote sensing satellite images within the port area, convert the vector elements into TIFF, and use a raster calculator Binarize the tiff, resample the tiff according to the port berth complexity, use GDAL to read the post-processing results and export a two-dimensional array of x*y, and save the array, range coordinates and pixel parameters to the database. When planning the route, the longitude and latitude coordinates of the ship's position are passed in, and the longitude and latitude coordinates are converted into Cartesian coordinate system coordinates according to the coordinate range and pixel parameters corresponding to the array. After the code reads the array, it performs a breadth-first search to obtain the route node set, and converts the node set from Cartesian coordinates. The system is converted into a geographical coordinate system, a GeoJson object is created and returned to the system as a result. The twin scene loads GeoJson to render the planned route.

The specific steps (4) are:

The twin scene establishes a two-way communication protocol with the radar data server. The radar data server analyzes the maritime interest ship targets currently tracked by the radar and pushes the basic information and geospatial parameters of the current target to the twin scene in real time. After receiving the data, the twin scene determines the scene. The rendering situation of the target ship. If the system tracks the target ship for the first time, the ship model is rendered and response events are added to it to display the basic information of the ship. If the target is continuously tracked by the system, the geospatial parameters of the ship are dynamically adjusted. Display the position and attitude of the ship in real time; calculate it through the browser window coordinates, that is, directly use the screen coordinates of the current radar model as the screen coordinates of the video control, and dynamically adjust it to the appropriate position through CSS, with the standard of not blocking other models. The video control is dynamically bound to the location of the radar model in the twin scene and automatically plays the real-time monitoring screen; through the conversion of maritime geographical coordinates and twin scene spatial coordinates, that is, using the Cesium spatial coordinate conversion function toolkit, the geographical coordinate system is converted to Cartesian Coordinate system, calculate the spatial coordinates of the locked ship and radar in the twin scene, draw a pyramid as the tracking light cone, the bottom surface of the pyramid faces the locked ship, and the top corner is at the position of the radar, use the keyframe animation function to adjust the light cone azimuth in real time Parameters to enable the light cone to continuously lock onto the tracked ship.

The advantages of the present invention are: the digital twin smart fishing port system based on oblique photography uses an unmanned aerial vehicle with an RTK (real-time dynamic carrier phase difference technology) positioning module to perform oblique photography modeling of the port area, and cooperates with professional modeling software The refined model produced is combined to build a three-dimensional scene of the fishing port, and the twin fishing port scenes are rendered and displayed on the Web to achieve low-cost, high-precision, and fast three-dimensional modeling of the fishing port. Utilize technologies such as IOT (Internet of Things) and data fusion to realize information exchange between virtual scenes and real scenes, and cooperate with mature artificial intelligence and other technologies to realize video fusion, radar tracking, berth management and other operations in the port area to achieve truly digital The smart fishing port system with twin capabilities solves a series of problems such as chaotic management, difficult supervision, and high costs in the traditional smart fishing port system, and provides a new technical solution for the implementation of the digital twin system of smart fishing ports.

This invention uses the three-dimensional real-life model produced by oblique photography as the main method, supplemented by the fine model produced by refined modeling, to build an efficient and realistic digital twin fishing port scene. The front end adopts open source WebGIS (network geography) such as Cesium or Maptalks. Information system) framework performs high-performance rendering and display of twin scenes, and cooperates with mature Internet technologies such as software and hardware equipment and IOT to complete twin functions such as video fusion, berth management, and radar tracking.

It also has the following advantages:

(1) High-performance rendering on the browser side, data is transmitted through the network, and can be seamlessly switched with traditional 2D fishing ports. Users do not need to install additional software or build an environment;

(2) It has the ability to display large-area fishing port 3D models. The 3D model is constructed using 3D real scenes at the macro level, with fast loading efficiency, high spatial accuracy and realistic textures. The microscopic model shows the details of the area of interest through refined modeling, providing users with an immersive experience. experience;

(3) Realize data and operation interoperability between the virtual and real worlds. The digital twin smart fishing port scene has functions such as video fusion, radar linkage, and berth management, effectively improving fishing port management and supervision capabilities.

Description of drawings

Figure 1 is a schematic flow diagram of the present invention.

Figure 2 is a schematic diagram of the route planning process of the present invention.

Figure 3 is a schematic diagram of the fishing port modeling process of the present invention.

Figure 4 is a schematic diagram of the basic data processing flow of berth route planning according to the present invention.

Figure 5 is a schematic diagram of the berth route planning process of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, these embodiments are only exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solution of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and substitutions all fall within the protection scope of the present invention.

Referring to Figures 1 to 5, the present invention relates to a method of building and using a digital twin smart fishing port based on oblique photography, including: (1) digital twin scene construction; (2) fishing port video fusion; (3) fishing port twin berth management; 4) Port area target radar tracking.

Described step (1) specifically includes:

(1-1) Drone flight: Conduct a flight survey on the fishing port area and use markup language to draw the aerial photography area to ensure coverage of the fishing port. The drone can automatically plan routes in the area after loading the markup language KML; in order to ensure tilt The accuracy of photogrammetry results, image control point measurement uses Qianxun Xingyao ; Check the fishing port environment before flying to determine whether the fishing port environment meets the requirements for flight. If the conditions are met, assemble the drone. After the drone self-test is correct, check whether the network RTK module is connected normally. Since there is currently no CORS (Continuous Operation Reference Station) If necessary to achieve nationwide coverage, you need to build a base station through RTK. When the RTK module is connected normally, fly according to the DJI Phantom 4 RTK tilt photogrammetry plan to complete the tilt photography work in the port area.

(1-2) Fishing port modeling: Export the original data from the drone, use ContextCapture software to sequentially perform image reading, first aerial triangulation, puncture point, second aerial triangulation and modeling, and generate Original 3D real-life model data in OSGB and OBJ formats ; in order to ensure model accuracy, the number of punctum points is flexibly adjusted according to the area of the survey area. The final output results are OSGB (commonly used oblique photography data storage format) and OBJ (3D model file format) ) data in two formats; since this process is time-consuming, a cluster can be built when necessary to improve production efficiency. Wherein, the first aerial triangulation is used to calculate the outer azimuth elements of each photo; the second aerial triangulation is used to improve the calculation accuracy of the outer azimuth elements of the photos and correct the model;

(1-3) Fishing port model repair: Due to the technical characteristics of oblique photography, some details of the model are lost. Although the accuracy of the model can be improved by flying at lower altitudes and height layering, it still cannot solve the problems of holes and deformation of the model. . Therefore, it is necessary to repair the model. Use ModelFun software to optimize the original 3D real-life model, import the OSGB and OBJ format data set model, and regenerate the OSGB data after the model repair is completed. Combined with the existing data, perform structural restoration, dock clearance, road screen installation, texture repair and other operations on the model. After the model repair is completed, ensure that there are no moving interference objects at the fishing port dock and re-export the data;

(1-4) Refined modeling of the fishing port: According to the modeling situation of the original three-dimensional real-life model, determine the areas in the port area that require refined modeling, and use 3Ds Max or Blender modeling software to conduct refined modeling. The modeling is completed. Then export it to OBJ format for use;

(1-5) Fishing port model rendering: Convert the repaired results into 3D Tiles format; use Cesium or MapTalks open source GIS framework to load 3D Tiles data on the browser side, adjust parameters based on project requirements, and realize front-end rendering of three-dimensional real-life scenes.

The browser cannot directly load slice data in OSGB and OBJ formats. Use software such as Cesium Lab or DasViewer to convert the repaired results into 3D Tiles format; 3DTiles is an open three-dimensional spatial data standard, and each 3D Tiles is saved by a It consists of a JSON (lightweight data exchange format) file of node information and several slicing package folders. By layering and hierarchical slicing processing of the model, the client realizes on-demand loading and rendering of the model; the conversion results are used as static resources using servers such as Nginx (high-performance HTTP and reverse proxy web server) for reverse proxy implementation. Request access; the browser uses the Cesium or MapTalks open source GIS framework to load 3D Tiles data, adjust the data parameters based on project requirements, and complete the front-end high-performance rendering of the 3D real-life scene.

The three-dimensional real-life scene has spatial information. The spatial coordinates are assigned to the refined production model and the model scaling is adjusted so that it can be displayed correctly in the three-dimensional real-life scene, thus realizing the construction of a digital twin smart fishing port scene.

The described step (2) is specifically: the purpose of fishing port video fusion is to project and fuse one or more surveillance videos in the fishing port area with the three-dimensional virtual scene related to the space, so that the virtual scene has real-time and realistic reflection monitoring. Screen capabilities, specifically:

(2-1) Carry out detailed modeling of the camera in the twin scene and load it to the corresponding location in the scene, and add a response event to it to control the opening or closing of the camera; when the event response is enabled, use the Cesium camera to create a view frustum to Simulate the visual range of the surveillance camera, and automatically switch the perspective of the twin scene to the corresponding position on the surveillance screen based on the camera position, azimuth angle and focal length parameters provided by the back-end interface;

(2-2) Adjust the camera's view cone so that the view cone correctly reflects the real camera focal length, angle and position; use Cesium's ShadowMap function to analyze the visual domain of the camera's view cone range;

(2-3) Create a video tag and generate a video texture by playing the video stream of HLS (HTTP streaming network transmission protocol) or FLV (streaming media format); use GLSL language to write texture processing logic, and the video content within the viewing cone can be The view area calculates the relative coordinates and shadow coordinates of the camera through the video texture and corresponding vertices in order to obtain the corresponding gl_FragColor. The shadow area retains the original texture of the model, achieving a combination of virtual and real, allowing users to watch real surveillance images in the virtual scene;

(2-4) In order to avoid video deformation caused by projection from affecting the visual experience, an additional set of video components is created to synchronously display the normal playback screen, and the video player is bound to the camera position in the twin scene through the callback function provided by Cesium. , when the user drags and drops the virtual scene, the video player will automatically follow the movement of the camera position in the scene.

The effect of video fusion is related to the viewing angle of the surveillance camera. The closer the viewing angle is to 90° with the surveillance surface, the smaller the screen projection distortion will be and the more realistic the experience will be. The video fusion effect completes the upgrade of the surveillance picture from two-dimensional to three-dimensional, achieving a combination of virtual and real. At the same time, the scene supports the surveillance video patrol function. Managers can implement comprehensive inspections of port area surveillance without any operation, effectively improving management and supervision efficiency.

The specific steps (3) are:

(3-1) Carry out intelligent twin management of berths in the port and provide a berth reservation function. Fishermen can check the map-based regional division and usage status of the berth in real time through the WeChat applet with reservation function, and select a vacant berth to make an online reservation. and intelligent path planning to achieve visualization of berth management and berth usage efficiency;

Open the WeChat applet, log in and enter the berth reservation interface, determine the current usage status of the berths in the port through the two-dimensional map and vector elements in the WeChat applet, and select the appropriate free berth for reservation.

(3-2) Use a two-dimensional map combined with vector elements to display the current usage status of berths in the port; select an idle berth to make a reservation, and after receiving the reservation command in the background, push the reservation information to the twin scene through websocket. The twin scene uses different colors The gradient color wall displays the real-time status of the berth; click on the berth to display the recent usage statistics of the berth; in the background, the coordinates and orientation information of the fishing vessel are obtained in real time through the positioning equipment installed on the fishing vessel, in conjunction with the near-port radar or monitoring screen, and the twin scenes are aligned based on the transmitted information. Fishing boats dock for route planning;

(3-3) Use the A* algorithm to provide necessary berth route planning for fishing boats. First, perform data preprocessing, vectorize the berths through remote sensing satellite images within the port area, convert the vector elements into TIFF, and use a raster calculator Binarize the tiff, resample the tiff according to the port berth complexity, use GDAL to read the post-processing results and export a two-dimensional array of x*y, and save the array, range coordinates and pixel parameters to the database. When planning the route, the longitude and latitude coordinates of the ship's position are passed in, and the longitude and latitude coordinates are converted into Cartesian coordinates based on the coordinate range and pixel parameters corresponding to the array. After the code reads the array, it performs a breadth-first search to obtain the route node set, and converts the node set from Cartesian to The coordinate system is converted into a geographical coordinate system, a GeoJson object is created and returned to the system as a result. The twin scene loads GeoJson to render the planned route.

The specific steps (4) are:

The twin scene establishes a two-way communication protocol with the radar data server. The radar data server analyzes the maritime interest ship targets currently tracked by the radar and pushes the basic information and geospatial parameters of the current target to the twin scene in real time. After receiving the data, the twin scene determines the scene. The rendering situation of the target ship. If the system tracks the target ship for the first time, the ship model is rendered and response events are added to it to display the basic information of the ship. If the target is continuously tracked by the system, the geospatial parameters of the ship are dynamically adjusted. Display the position and attitude of the ship in real time; calculate it through the browser window coordinates, that is, directly use the screen coordinates of the current radar model as the screen coordinates of the video control, and dynamically adjust it to the appropriate position through CSS, with the standard of not blocking other models. The video control is dynamically bound to the location of the radar model in the twin scene and automatically plays the real-time monitoring screen; through the conversion of maritime geographical coordinates and twin scene spatial coordinates, that is, using the Cesium spatial coordinate conversion function toolkit, the geographical coordinate system is converted to Cartesian Coordinate system, calculate the spatial coordinates of the locked ship and radar in the twin scene, draw a pyramid as the tracking light cone, the bottom surface of the pyramid faces the locked ship, and the top corner is at the position of the radar, use the keyframe animation function to adjust the light cone azimuth in real time The parameters enable the light cone to continuously lock on the tracked ship. Even if the ship positions in the target area are densely distributed, the manager can clearly understand the current radar locked ship.

Considering development costs and hardware performance limitations, data transmission will not be continuous and will be pushed every few seconds. Interpolate the two points before and after to make the movement route of the ship in the scene continuous and uniform, and avoid the phenomenon of ship position jumping.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can, within the technical scope disclosed in the present invention, implement the technical solutions of the present invention. Equivalent substitutions or changes of the inventive concept thereof shall be included in the protection scope of the present invention.

Claims (5)

1. The method for constructing and using the digital twin intelligent fishing port based on oblique photography is characterized by comprising the following steps of:

(1) Digital twin scene building; (2) video fusion of fishing ports;

(3) Management of twin berths of a fishing port; 4) And (5) port area target radar tracking.

2. The method for constructing and using the digital twin intelligent fishing port based on oblique photography according to claim 1, wherein the step (1) specifically comprises:

(1-1) unmanned aerial vehicle aerial photography: after investigation of oblique photography flight conditions of the fishing port area, drawing an aerial photography area covering the fishing port through a mark language; in order to ensure the precision of the oblique photogrammetry result, the selection of the image control points should be uniformly distributed in the harbor area; after carrying out image control point marking by spraying or selecting a marked ground object on the ground, carrying out image control point measurement by using RTK equipment;

namely: checking the fishing port environment before flying, judging whether the current environment condition meets the flying or not, and if the current environment condition meets the flying, assembling the unmanned aerial vehicle, and starting aerial photography work when the unmanned aerial vehicle self-tests without errors and normally uses the RTK module;

(1-2) fishing port modeling: the method comprises the steps of deriving shot original data from an unmanned aerial vehicle, sequentially carrying out original data reading, first air triangulation, stabbing point, second air triangulation and modeling by using ContextCapture software, and generating original three-dimensional real scene model data in two formats of OSGB and OBJ, wherein the first air triangulation is used for calculating external azimuth elements of each photo; the second time of aerial triangulation is used for improving the calculation accuracy of the external azimuth angle elements of the photo and correcting the model;

(1-3) fishing port model repair: optimizing an original three-dimensional live-action model by using ModelFun software, importing an OSGB and OBJ format data set model, and regenerating OSGB data after finishing the model repair;

(1-4) fishing port fine modeling: determining a region needing to be modeled finely in a harbor area according to the modeling condition of the original three-dimensional live-action model, performing fine modeling by modeling software, and generating an OBJ model after modeling is finished;

(1-5) fishing port model rendering: converting the repaired result into a 3D tilles format; the browser end loads 3D Tiles data by using a Cesium or MapTalks open source GIS frame, and adjusts parameters according to project requirements, so that the front end renders a three-dimensional real scene.

3. The method for constructing and using the digital twin intelligent fishing port based on oblique photography according to claim 1 or 2, wherein the step (2) is specifically:

(2-1) carrying out refined modeling on a camera in a twin scene, loading the camera into a corresponding position of the scene, and simultaneously adding a response event for the camera to control the opening or closing of the camera; when an opening event responds, a viewing cone is created by using a Cesium camera to simulate the visual range of a monitoring camera, and the visual angle of a twin scene is automatically switched to the corresponding position of a monitoring picture according to the position, azimuth angle and focal length parameters of the camera provided by a rear-end interface;

(2-2) adjusting a camera view cone to enable the view cone to correctly reflect the real focal length, angle and position conditions of the camera; performing visual field analysis processing on the camera view cone range by using a shadow map function of Cesium;

(2-3) creating a video tag, and generating video textures by playing the monitor video stream picture; writing texture processing logic by using GLSL language, sequentially calculating relative coordinates and shadow coordinates of a visible area in a viewing cone range and a camera through video textures and corresponding vertexes to obtain corresponding gl_FragColor, and reserving original textures of a model in the shadow area;

(2-4) in order to avoid the influence of video deformation caused by projection on visual experience, additionally creating a group of video components to synchronously display the play pictures in a normal state, and binding the video player and the camera positions in the twin scene through a callback function provided by Cesium.

4. The method for constructing and using the digital twin intelligent fishing port based on oblique photography according to claim 1 or 2, wherein the step (3) is specifically:

(3-1) carrying out intelligent twin management on the berths in the harbor, providing a berth reservation function, checking the regional division and the use state of the berths based on a map in real time by fishermen, and selecting spare berths to carry out online reservation and intelligent path planning;

(3-2) displaying the use state of the berth in the current harbor in a two-dimensional map combined with vector elements in a WeChat applet; selecting an idle berth for reservation, pushing reservation information to a twin scene through websocket after a background receives a reservation command, and displaying the real-time state of the berth by the twin scene through gradient color walls with different colors; clicking a berth to display the statistics information of the use of the berth in the near day; the background acquires the coordinates and azimuth information of the fishing boat in real time by using positioning equipment installed on the fishing boat and matching with a near-harbor radar or a monitoring picture, and the twin scene carries out route planning on the berthing of the fishing boat according to the transmission information;

and (3-3) providing necessary berth route planning for the fishing vessel by utilizing an A-algorithm, firstly carrying out data preprocessing, vectorizing berths through a remote sensing guard diagram of a harbor area range, converting vector elements into TIFF, carrying out binarization processing on the TIFF by utilizing a grid calculator, resampling the TIFF according to harbor berth complexity, reading a post-processing result by utilizing GDAL, deriving a two-dimensional array of x y, storing an array, range coordinates and pixel parameters into a database, transmitting longitude and latitude coordinates of the berth during route planning, reading the array by codes, converting the longitude and latitude coordinates into rectangular coordinate system coordinates according to a coordinate range and pixel parameters corresponding to the array, carrying out breadth-first search in the array, obtaining a route node set, converting the node set into the geographic coordinate system from the rectangular coordinate system, creating a GeoJson object as a result, and returning the GeoJson object to the system, so that the route planning can be rendered by loading a twin scene.

5. The method for constructing and using the digital twin intelligent fishing port based on oblique photography according to claim 1 or 2, wherein the step (4) is specifically:

the method comprises the steps that a two-way communication protocol is established between a twin scene and a radar data server, and the radar data server pushes basic information and geospatial parameters of a current target to the twin scene in real time by analyzing the target of a marine interesting ship tracked by the current radar; after receiving data, the twin scene judges the rendering condition of a target ship in the scene, if the system tracks the target ship for the first time, a ship model is rendered, a response event is added for the ship model to display basic information of the ship, and if the target is in continuous tracking of the system, the geospatial parameters of the ship are dynamically adjusted, and the position and posture conditions of the ship are displayed in real time; calculating through a browser window coordinate, namely directly taking the screen coordinate of the current radar model as the screen coordinate of the video control, dynamically adjusting to a proper position through CSS, dynamically binding the video control to the position of the radar model in the twinning scene and automatically playing a real-time monitoring picture by taking the non-shielding other models as the standard; through the transformation of the marine geographic coordinates and the space coordinates of the twin scene, namely by utilizing a Cesium space coordinate transformation function tool kit, the geographic coordinate system is transformed into a Cartesian coordinate system, the space coordinates of the locked ship and the radar in the twin scene are calculated, a pyramid is drawn to serve as a tracking light cone, the bottom surface of the pyramid faces the locked ship, the vertex angle is positioned at the radar position, and the azimuth angle parameters of the light cone are adjusted in real time by utilizing a keyframe animation function, so that the light cone is continuously locked on the tracked ship.