A method and system for making a three-dimensional geographic PDF map

Abstract

The application provides a three-dimensional geographic PDF map making method and system, the method comprising: obtaining and analyzing three-dimensional map data, including projection mode, geometric data, attribute data and the like; constructing a U3D (Universal 3D) data object, converting and storing the three-dimensional map data into a U3D data format; based on a three-dimensional geographic PDF map model, organizing the three-dimensional map data into a 3D Artwork structure in a PDF file format by respectively constructing a 3D Annotation structure, a 3D Stream structure and a 3D View structure; and outputting a PDF file, thereby obtaining a three-dimensional geographic PDF map. The application can organize, store, transmit and express three-dimensional map data by using a PDF document, thereby expanding the application field of three-dimensional maps.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geographic PDF map, in particular to a three-dimensional geographic PDF map making method and system. BACKGROUND

[0002] PDF (Portable Document Format) is a file format designed and developed by Adobe Company in 1993, which is used to present documents in a way independent of application software, hardware and operating system, and can output all required data on terminal such as screen and printer. PDF has become an ideal document format in digital information dissemination due to its advantages of cross-terminal display, small file size, fast speed, simple editing, etc. The idea of geographic PDF map was proposed in China in 2004, and the research on GeoSpatial PDF was started in the United States in the same year. Raytheon Image Corporation proposed in 2004 to use GeoPDF file format to store maps and geographic information. GeoPDF integrates document information such as graphics, images and text and geographic spatial information on the basis of PDF standard specification, expands map functions such as map layering and browsing and information labeling, and makes multi-layer maps and images in PDF file format.

[0003] The research and development of geographic PDF map in China are developing rapidly. Geographic PDF map is to store map data by using PDF file format. The research on geographic PDF map is currently focused on making two-dimensional geographic PDF map by using two-dimensional map data, and cannot realize the making and use of geographic PDF map for three-dimensional map data. With the development of technology, three-dimensional map data with high quality and high information density are increasingly accepted by the public, and users also have high use demand for three-dimensional map data. SUMMARY

[0004] A main problem solved by the present application is to solve the problem that the existing geographic PDF map cannot make map for three-dimensional map data.

[0005] The present application provides a three-dimensional geographic PDF map making method, which comprises:

[0006] acquiring three-dimensional map data and parsing to obtain parsed data;

[0007] converting the parsed data into U3D data format;

[0008] storing the parsed data in U3D format into 3D Artwork structure of PDF file format based on a preset three-dimensional geographic PDF map model, and generating a three-dimensional geographic PDF map.

[0009] Preferably, the three-dimensional map data is acquired and parsed to obtain parsed data, including:

[0010] The three-dimensional map data is acquired, and a data source data type is set.

[0011] The three-dimensional map data of the corresponding type is parsed to obtain corresponding parsed information.

[0012] Preferably, the data source data type includes:

[0013] The terrain model data and the ground object model data are constructed based on the three-dimensional map data.

[0014] Preferably, the parsed data is converted into a U3D data format, including:

[0015] The U3D data object is constructed based on the characteristics of the parsed information.

[0016] The parsed information is set into the U3D data object to obtain the parsed data converted into the U3D format.

[0017] Preferably, the parsed information is set into the U3D data object to obtain the parsed data converted into the U3D format, including:

[0018] The point position, the point normal vector, the face position, the face normal vector, and the texture information in the parsed information are input into the U3D data object to generate the parsed data in the U3D format.

[0019] Preferably, the parsed data in the U3D format is stored into the constructed 3D Artwork structure, including:

[0020] The parsed data in the U3D format is stored into the three-dimensional stream structure of the constructed 3D Artwork.

[0021] Preferably, the running steps of the preset three-dimensional geographic PDF map model include:

[0022] The three-dimensional geographic PDF map model takes a catalog as a root node, passes through a page cluster, and then passes through a page node to access the 3D Artwork.

[0023] The 3D Annotation structure of the 3D Artwork provides a viewpoint for viewing the 3D Artwork, the 3D Stream structure is used for packaging and storing the three-dimensional map data in the U3D format, and the 3D View structure controls the display parameters of the three-dimensional geographic PDF map.

[0024] According to another aspect of the present application, there is also provided a three-dimensional geographic PDF map making system, which is used for implementing the three-dimensional geographic PDF map making method according to any one of the preceding aspects when in operation, and the three-dimensional geographic PDF map making system comprises:

[0025] a data parsing module, configured to acquire and parse three-dimensional map data, and acquire parsed data;

[0026] a data format conversion module, configured to convert the parsed data into U3D data format;

[0027] a three-dimensional geographic PDF map generation module, configured to store the parsed data in U3D format into a 3D Artwork structure in PDF file format according to a three-dimensional geographic PDF map model, and generate a three-dimensional geographic PDF map.

[0028] The present application provides a three-dimensional geographic PDF map making method, which is used for expanding the data types that can be carried by a geographic PDF map, increasing the expression content of the geographic PDF map, providing a new three-dimensional map data expression, making and transmission model for professional personnel, and also providing a new type of three-dimensional map product for users. The three-dimensional geographic PDF map can well promote the use of the three-dimensional map, and reduce the threshold for non-professional users to use the three-dimensional map data. The three-dimensional geographic PDF map combines the characteristics of the three-dimensional map data structure and the PDF document format structure, connects the three-dimensional map data and the PDF file format by using a U3D (Universal 3D) three-dimensional data model, so that the three-dimensional map data can be stored, transmitted and displayed in the PDF document. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings, which constitute a part of this specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0030] Figure 1 is a flowchart of the three-dimensional geographic PDF map making method according to the present application;

[0031] Figure 2 is a classification schematic diagram of the three-dimensional map model in the embodiment of the present application;

[0032] Figure 3 is a construction flowchart of the U3D (Universal 3D) data in the embodiment of the present application;

[0033] Figure 4 is a conversion schematic diagram of the DEM data converted into the U3D data in the embodiment of the present application;

[0034] Figure 5 is a three-dimensional geographic PDF map model structure diagram in the embodiment of the present application. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0036] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0037] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0038] 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 specific embodiments and accompanying drawings.

[0039] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0040] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0041] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0042] Example 1: First, the 3D map data is converted into the 3D data format required for creating a 3D geographic PDF map, namely U3D format. This clarifies the spatial reference and organization of the 3D map data to facilitate the creation of the 3D geographic PDF map. The acquired and parsed 3D map data is then used to construct the 3D Artwork structure within the PDF structure. Finally, the PDF file storing the 3D map data and related parameter information is output, resulting in the 3D geographic PDF map. The following section combines... Figure 1 This section explains the specific steps involved in creating a 3D geographic PDF map.

[0043] Step 1: Acquire and parse 3D map data. The specific process is as follows:

[0044] 1. The model type of three-dimensional map data can be divided into feature model data and terrain model data. Different models contain data with different characteristics. The model at least contains geometric information and texture material information, and can support data types such as artificial modeling three-dimensional model data, real scene three-dimensional data including oblique photography modeling data and point cloud data, building information model data and vector data. The three-dimensional map model obtained in the embodiment can be processed from basic data or constructed based on public data.

[0045] 2. Obtain three-dimensional map data and determine the data source data type. According to CH / T 9015-2012 “Three-dimensional geographic information model data product specification” or other three-dimensional geographic information model data product standards, the three-dimensional map model is composed of a terrain model and a feature model. The terrain model is a three-dimensional model used to represent the undulating form of the ground, and is usually based on a digital elevation model, with a digital orthophoto map (DOM) attached to the DEM surface to realize three-dimensional description of the undulating form of the ground. As shown in FIG. 1, the feature model can be further divided into seven categories, including building element model, traffic element model, water system element model, vegetation element model, site model, pipeline and underground space facility element model, and other element model, but is not limited to the seven categories. Figure 2

[0046] 3. Analyze the three-dimensional map data to parse the corresponding map projection information, three-dimensional geographic element information, geometric data information, attribute information, etc. of the feature model or the terrain model. Specifically, read the three-dimensional map data, and obtain specific data according to the model category. For example, from the feature model, obtain the point, line, surface, etc. geometric information that constitutes the feature model, and store it in the form of coordinate value and elevation value. Then, obtain the texture and material of each surface of the feature model. If the feature model contains attribute information, further analyze the attribute information, and store it in the form of key-value pair under the same directory of the three-dimensional geographic PDF map model. From the terrain model, obtain the geometric information describing the terrain undulation in the terrain model, which should include elevation information and texture material information.

[0047] 4. Determine the spatial reference conversion relationship between the three-dimensional map data and the three-dimensional geographic PDF map. The spatial reference should be consistent with that of the three-dimensional map data, and a unified spatial reference conforming to the national regulations of the plane coordinate and elevation system should be used to organize the spatial reference of the three-dimensional geographic PDF map. When organizing the three-dimensional geographic PDF map model data, coordinate system conversion is needed. The coordinate system in the three-dimensional map model is converted into the coordinate system of 3D Artwork in the three-dimensional PDF map document, which specifically includes two conversion processes, one is the conversion process between geographic coordinate systems, and the other is the conversion process between projection coordinate systems. ​

[0048] Geographic coordinate system is a spherical coordinate system established with reference to the reference ellipsoid. The coordinate unit is longitude and latitude. When the three-dimensional geographic PDF map selects a reference ellipsoid different from the three-dimensional map data to establish a geographic coordinate system, conversion between geographic coordinate systems should be performed.

[0049] The projection coordinate system is a plane coordinate. The conversion of the geographic coordinate system to the projection coordinate system is also called map projection. The conversion relationship depends on the projection method. The projection method is classified according to the deformation property, including equal-angle projection, equal-area projection, and arbitrary projection. According to the projection surface type, there are horizontal cylindrical projection, conic projection, and azimuthal projection. According to the relationship between the projection surface and the earth position, there are normal axis projection, oblique axis projection, transverse axis projection, tangent projection, and secant projection. There is a strict mathematical conversion relationship between different projection coordinate systems.

[0050] Step two: convert and store the three-dimensional map data into U3D data format.

[0051] The architecture of U3D data object is based on the interaction of five key elements, namely, palette, node, scene graph, resource, and modifier chain.

[0052] The following will be combined Figure 3 Briefly describe the U3D structure mainly involved in converting three-dimensional digital maps.

[0053] The palette is used to control access to nodes and resources. Each type of palette controls the corresponding type of node and resource.

[0054] First, set the scene graph, which is used to maintain the hierarchical relationship and spatial relationship between nodes.

[0055] Then set each node and node resource. Nodes and node resources contain most of the information when creating 3D Artwork. Nodes themselves have spatial relationships and hierarchical relationships. Node types include groups, models, lights, and views. Each type of node corresponds to a node resource. Among them, the group node only contains spatial and hierarchical structure information, and has no resource information.

[0056] View resources contain information about rendering, fog, and scene graphs.

[0057] Model resources contain information for creating renderable geometry.

[0058] Light resources contain information specific to lights, such as the type of light.

[0059] Then set the element array.

[0060] Then set the following content:

[0061] Setting the color resource, the color resource is the content of the storage of three-dimensional digital map appearance description information, which controls the visual appearance of the geometry. Color resources include texture resources, material resources and lighting texture color resources.

[0062] Setting the texture resource and material resource, the texture resource is the image data applied to the geometry, which contains image data and compression method information. Material resources are used to describe the appearance of the surface of the geometry at the lowest level. Lighting texture color resources explain in detail how the material and texture used when rendering geometry are combined.

[0063] Finally, set the modifier chain, which contains multiple modifiers, controls data related to resources, nodes and textures, and is a data processing chain formed by multiple data operators.

[0064] The specific process of constructing the U3D structure is as follows:

[0065] 1. According to the characteristics of the three-dimensional map data obtained and parsed, a U3D data object is established for storing the corresponding information.

[0066] 2. After establishing the U3D data object, set the lighting parameters, geometry information, material information and other data parsed from the three-dimensional map data into the U3D data object. As mentioned earlier, according to CH / T 9015-2012 "Three-dimensional geographic information model data product specification", three-dimensional map models can be divided into terrain models and feature models, and feature models can be further divided into seven types of building element models, traffic element models, water system element models, etc., but not limited to these seven types.

[0067] The Model structure in the U3D data object is used to store the three-dimensional map models mentioned above. For different types of three-dimensional map models, the Group structure can be used for classification, and then the map layering is realized. The Node structure is used to organize the association relationship between map features.

[0068] For geometry data, the U3D data object provides three element types: point, line, and mesh. Taking DEM data to express terrain data as an example, DEM data is composed of grid data, which corresponds to the mesh element in the U3D data object.

[0069] Each group of mesh elements in the U3D data object is called a mesh group. The mesh group is composed of a point array and a face array. Each vertex in the point array contains position, normal, and texture coordinate attributes.

[0070] The step of inputting the geometry and texture data obtained from the three-dimensional map model into the corresponding mesh group is: the point position and point normal vector of the DEM model can be directly stored in the point array and point normal vector array of the U3D data object. Each face in the face array is organized according to the three vertex position indexes of the point array, and each index corresponds to a triangle, so the face array and the face normal vector array store the vertex position index and the point normal vector index. The texture data input is to correspond the texture coordinates with the geometry coordinates. This method is suitable for the conversion of the geometric shape information of the feature model.

[0071] In addition, the attribute of the element in the three-dimensional map model can be converted by storing the node attribute value of the corresponding geometry in the node metadata of the U3D data object, including the name, length, area and other text or numerical values of the point, line, face and volume elements.

[0072] For example: set the three-dimensional map data parsed in the previous step into the U3D data object. In the setting process, the three-dimensional map data needs to be reorganized into a three-dimensional object supported by the U3D format according to the U3D model data structure. The feature objects and terrain objects in the three-dimensional map data, such as roads, water bodies and terrain, are organized according to the Model structure. Taking the DEM data to express the terrain data as an example, the geometry information and texture information in the feature model and the terrain model are converted according to the following methods:

[0073] The DEM model in the terrain model is composed of mesh data, which corresponds to the mesh element in the U3D model. The U3D model provides three element types: point, line and mesh. Each group of mesh elements in the U3D model is called a mesh group. The mesh group is composed of a point array and a face array. Each vertex in the point array contains position, normal and texture coordinate attributes. Assuming that the coordinates of the four vertices of a mesh in the DEM model are (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3) and (X4, Y4, Z4), and the normal vectors corresponding to the four vertices are (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3) and (X4, Y4, Z4), the conversion method of point data and face data is as follows: 3, 11 11 11 22 22 22 33 34 34 44 44 44 Figure 4 ​​​​​​​​​​​​​The geometry information and texture material information obtained from the three-dimensional map model are respectively input into corresponding mesh groups. The point position and point normal vector of a digital elevation model (DEM) can be directly stored in a point array and a point normal vector array of a U3D model, and each face in a face array is organized according to three vertex position indexes of the point array, each index corresponding to a triangle, so that the face array and the face normal vector array store vertex position indexes and point normal vector indexes. Texture data input is to correspond texture coordinates with geometry coordinates. Attribute data can be converted by storing node attribute values of corresponding geometry graphics in node metadata of the U3D model, including names, lengths, areas and other texts or values of point, line, face and body elements.

[0074] Step three: based on the three-dimensional geographic PDF map model, relevant data is organized into a 3D Artwork structure of the PDF file.

[0075] The working principle of the preset three-dimensional geographic PDF map model is as follows: the three-dimensional geographic PDF map takes a directory object as a root node, accesses to a 3D Artwork used for storing and managing a three-dimensional map model through a page cluster and a page node, as shown in Figure 5 .

[0076] Specifically, the page cluster (Pages) contains a page node, which controls a page (Page) in the PDF document. The page is an important component in the three-dimensional geographic PDF map and is also a structure carrying the 3D Artwork.

[0077] In the PDF document structure, a structure used for organizing and managing a three-dimensional model is called a 3D Artwork (three-dimensional object), and three-dimensional map data is expressed as a 3D Artwork in the PDF document structure.

[0078] A 3D Artwork contains three necessary structures for supporting storage and management of a three-dimensional map model, which are a 3D Annotation (three-dimensional annotation), a 3D Stream (three-dimensional stream) and a 3D View (three-dimensional view).

[0079] The 3D Annotation is an entrance for describing and expressing all methods of the 3D Artwork, which provides a viewpoint for viewing the 3D Artwork.

[0080] The 3D Stream is used for storing three-dimensional map data, and the PDF specification 1.7 supports a three-dimensional data model in a U3D format.

[0081] 3D View is associated with the display of 3D Artwork, which provides the relevant parameters of the viewpoint in 3D Annotation, such as the position, direction, coordinate system, etc. of the viewpoint.

[0082] 3D Stream in 3D Artwork is a PDF object for storing and managing U3D data objects, which packages and compresses U3D data objects into binary files and stores them in 3D Stream. Then, the projection method of the map in 3D View is set, etc. Setting 3D View can provide different viewing angles for the viewer when opening a three-dimensional PDF map document. 3D View is set through the view object dictionary.

[0083] The specific process of constructing 3D Artwork is as follows:

[0084] 1. Construct 3D Annotation structure.

[0085] 3D Annotation provides a virtual camera for viewing three-dimensional data. 3D Annotation is the entry for all methods of describing and expressing 3D Artwork, which includes the entry of 3D Stream and 3D View. The 3D Annotation structure contains a description dictionary object. The dictionary structure is organized in the form of "Key-Type-Value". The description dictionary of 3D Annotation provides the access entry of 3D Stream and 3D View, and the specific method can be set by corresponding to the Value with Key value "3DD" and "3DV" respectively.

[0086] 2. Construct 3D Stream structure.

[0087] 3D Stream is a structure for storing three-dimensional data, which can provide default view and predefined view. The 3D Stream structure also contains a description dictionary object and a reference dictionary object. The "VA" field in the description dictionary represents an array of 3D View description dictionary, which contains multiple 3D View description dictionaries. Through this field entry, the array of 3D View description dictionaries is stored in the structure. The optional field "Resources" is a name tree structure, which contains objects that can be used to modify the initial appearance of 3D Artwork. The "3DD" field in the reference dictionary object is the stream type, which is used for the storage of three-dimensional data. U3D data is stored through this entry.

[0088] 3. Construct 3D View structure.

[0089] In the 3D View structure, parameters to be applied to the virtual camera associated with the 3D Annotation are specified, including the square and position of the camera, transformation parameters of the camera coordinate system to the target coordinate system, etc. The role of the 3D View structure is to specify the parameters to be applied to the virtual camera associated with the 3D Annotation, which contains a description dictionary object. Among them, the fields that need to be set are "XN", "U3DPath", "P", which respectively refer to view name, U3D data path and projection information.

[0090] Step four: outputting the three-dimensional geographic PDF map based on the preset three-dimensional geographic PDF map model.

[0091] The overall main part can be divided into the following three links:

[0092] 1. Analyze the control PDF structure, such as Doc, Page, Object, 3D Artwork, etc., wherein the 3D Artwork structure is the key part. The main structure of 3D Artwork has three blocks of 3D Annotation, 3D Stream and 3D View. 3D Annotation provides a virtual camera for viewing three-dimensional data. 3D Stream is a structure responsible for three-dimensional data storage, and U3D data objects are stored in 3D Stream. 3D View controls all parameters required for display, such as user perspective, coordinate system parameters, etc.

[0093] 2. Implement the storage of three-dimensional map data using U3D data objects, parse U3D data structure, input point position, point normal vector, face position, face normal vector and texture information in three-dimensional data into U3D data object, and generate U3D data.

[0094] 3. Complete the construction of 3D Artwork in PDF, store the U3D data generated in the previous step, and generate a PDF file, that is, obtain a three-dimensional geographic PDF map.

[0095] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle range of the present application should be included in the protection range of the present application.

[0096] It is also to be noted that the terms "comprising", "including", and any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a... " does not, without further restriction, exclude the existence of additional elements of the process, method, article, or apparatus that comprises the element.

Claims

1. A method for creating a three-dimensional geographic PDF map, characterized in that, The method for creating a 3D geographic PDF map includes: Acquire and parse 3D map data to obtain parsed data, including: Acquire 3D map data and set the data source data type; The 3D map data includes: oblique photogrammetry modeling data and point cloud data, real-scene 3D data, building information model data, and vector data; the data source data types include: terrain model data and feature model data constructed based on the 3D map data; the terrain model data is a 3D model used to represent the undulating shape of the ground, based on a digital elevation model, with digital orthophoto maps attached to the DEM surface to achieve a 3D description of the undulating shape of the ground; the feature model data includes: building element models, transportation element models, water system element models, vegetation element models, site models, and pipeline and underground space facility element models; Parse the corresponding type of 3D map data to extract the map projection information, 3D geographic feature information, geometric data information and attribute information of the corresponding feature model or terrain model, and obtain the corresponding parsing information; Converting the parsed data into U3D data format includes: Based on the characteristics of parsed information, U3D data objects are constructed; U3D data objects provide three element types: points, lines, and meshes; The parsed information is set into a U3D data object to obtain parsed data converted to U3D format; The parsed information is set into a U3D data object to obtain parsed data converted to U3D format, including: The point positions, point normals, face positions, face normals, and texture information from the parsed information are input into a U3D data object to generate parsed data in U3D format; The Model structure in the U3D data object is used to store the 3D map data; the Group structure in the U3D data object classifies different types of 3D map data, thereby realizing map layering. The Node structure in U3D data objects is used to organize the relationships between map features; Determine the spatial reference transformation relationship between 3D map data and a preset 3D geographic PDF map model, specifically including: geographic coordinate system transformation and projected coordinate system transformation; Based on a pre-defined 3D geographic PDF map model, the parsed data in U3D format is stored in the 3DArtwork structure of the PDF file specification to generate a 3D geographic PDF map.

2. The method for creating a three-dimensional geographic PDF map as described in claim 1, wherein, The parsed data in U3D format is stored in the constructed 3D Artwork structure, including: The parsed data in U3D format is stored in the 3D Stream structure of the constructed 3D Artwork.

3. The method for creating a three-dimensional geographic PDF map as described in claim 1, wherein, The steps for running a pre-defined 3D geographic PDF map model include: The 3D geographic PDF map model uses the directory as the root node, passes through page clusters and then through page nodes to access the 3D Artwork. The 3D Annotation structure of the 3D Artwork provides a viewpoint for viewing the 3D Artwork, the 3D Stream structure is used to package and store 3D map data in U3D data format, and the 3D View structure controls the display parameters of the 3D geographic PDF map.

4. A three-dimensional geographic PDF map creation system, characterized in that, The 3D geographic PDF map creation system is used to implement a 3D geographic PDF map creation method as described in any one of claims 1-3. The 3D geographic PDF map creation system includes: The data parsing module is used to acquire and parse 3D map data, and obtain the parsed data. A data format conversion module is used to convert the parsed data into U3D data format; The 3D geographic PDF map generation module, based on the 3D geographic PDF map model, is used to store the parsed data in U3D format into a 3D Artwork structure in PDF file format and generate a 3D geographic PDF map.

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