第 3 章 矢量数据模型（第 1 讲）

1. 第3章 矢量数据模型（第1讲） 教学内容： 3.1 简单要素的表示；3.2 拓扑 教学目的： 1、让学生掌握简单要素和拓扑的概念； 2、通过三角网、分区和路径等例子介绍让学生掌握复合要素 教学重点：三角网、分区和路径的相关知识点 教学难点：分区和路径怎样在Coverage、Shapefiles和Geodatabase中进行不同的处理 教学时间：2课时 教学方法：讲授法和多媒体教学法 本课程涉及的教学前沿

2. How does a computer “see” map features?计算机如何“看”地图要素？ • Vector data model矢量数据模型 • Uses x, y coordinates of points to represent points, lines, areas 用点的 x, y 坐标来代表点、线、面 • Organizes geometric objects thus represented into digital data files 将如此表示的几何对象组织成数字化数据文件

3. Vector Data Model To prepare spatial data for computer processing, the vector data model first uses points and their x-, y-coordinates to represent spatial features as points, lines, and areas. Then it organizes geometric objects and their spatial relationships into digital data files that the computer can access, interpret, and process. 为使计算机能够处理空间数据，矢量数据模型的数据备制一般包括以下两个基本步骤：首先使用点和它们的X，Y坐标来表示空间要素如点，线，面。然后，它将几何对象及其空间关系组织成数字化数据文件，使计算机可以访问、编译和处理。

4. Figure 3.1 A reference map showing Idaho and lands held in trust by the United States for Native Americans. 显示爱达荷州和该州由美国为土著美洲人代管土地及周边州县的参考地图

5. Evolution of Vector Data Model矢量数据模型的演变 • ESRI, Inc. • Arc/Info: coverages • ArcView: shapefiles • ArcGIS: geodatabase 基于对象数据模型 地理相关数据模型

6. 3.1 Representation of Simple Features简单要素的表示 • Vector data model 矢量数据模型 • Uses geometric objects of point, line, area to represent spatial features • 用点、线、面等几何对象表示空间要素 Figure 3.3 Point, line, and area features.

7. Point • Zero dimensions（0维） • No length, width or height, only location implied（没有长度，宽度或高度，但是具有定位功能） • Defined by x, y coordinates（通过x, y 坐标定义） • Also called a node or vertex（也叫做节点或顶点） • Examples: wells, buildings, surveymarkers 例如：井、建筑物、测量标记

8. Line • One-dimensional（1维） • Properties of length and location（长度和定位特征） • Defined by x, y coordinates of its end points and (if curved) of points along its path • Lines also known as edges, links（边线，链接） • Examples: roads, streams, contour lines 例如：道路、河流、等高线

9. Area • Two-dimensional (length and width) • Properties of area and perimeter • Defined by its boundary line (which is defined by its points) • Also called polygon • Examples: political entities, water bodies 例如：行政区、水体

10. Map Scale 地图比例尺 • Representation of map features dependent on map scale 地图要素的表示取决于地图比例尺 • A city at 1:1,000,000 may appear as a point, but at 1: 24,000 it will be anarea 一个城市在 1:1,000,000 地图以一点出现，在1: 24,000 则为一个区域 • Government mapping standards 政府制图标准

11. 3.2 Topology 拓扑 • Explicit expression of spatial relationship between features 要素空间关系的清晰表达 • Graph theory • Directed lines – arcs 弧段 • Nodes - points where arcs meet or intersect 结点- 弧段会合点或交叉点

12. Topology • Topologyis the study of those properties of geometric objects that remain invariant under certain transformations such as bending or stretching. 拓扑是研究几何对象在弯曲或拉伸等变换下仍保持不变的性质 • Diagrams or graphs are used in topology for studying the arrangements of geometric objects and the relationships between objects. 图表或图形中使用的拓扑结构来研究几何对象排列及其相互关系。

13. Figure 3.4 The adjacency matrix and incidence matrix for a digraph. （有向图的邻接矩阵和关联矩阵）

14. 3.2.1 TIGER • Topologically Integrated Geographic Encoding and Referencing 拓扑综合地理编码参照格式 • U.S. Census Bureau database 美国人口普查局数据库 • Defined spatial relationships between points, lines, and areas 在点、线、面之间定义空间关系

15. Figure 3.5 Topology in the TIGER database involves 0-cells or points, 1-cells or lines, and 2-cells or areas.

16. Figure 3.6 Address ranges and zip codes in the TIGER database have the right- or left-side designation based on the direction of the street.

17. 3.2.2 ESRI’s Coverage Model • Model introduced in the 1980s to separate CAD from GIS • Supports three basic topological relationships • Connectivity 联通性 • Area definition 面积定义 • Contiguity 邻接性

18. 3.2.3 Coverage Data Structure • Incorporates topological relationships into data structure 使拓扑关系与数据结构一体化 • Contains feature IDs and x-y coordinate pairs 含要素标识号和 x-y 坐标对

19. Figure 3.7 The data structure of a point coverage.

20. Figure 3.8 The data structure of a line coverage.

21. Figure 3.9 The data structure of a polygon coverage.

22. 3.2.4 Importance of Topology 拓扑重要性 • Assurance of data quality 确保数据质量和完整性 • Error detection 查错 • Enhance GIS analysis 可强化GIS 分析 • Networks (streets, utilities) 网络（街道、设施）

23. Figure 3.10 A polygon coverage, shown in a, has topological errors. Each small square symbol represents an error caused by lines that do not meet correctly. The shapefile, shown in b, is converted from the polygon coverage.

24. 第3章 矢量数据模型（第2讲） 教学内容： 3.3 地理相关数据模型；3.4 基于对象数据模型 教学目的： 1、让学生掌握简单要素和拓扑的概念； 2、通过三角网、分区和路径等例子介绍让学生掌握复合要素 教学重点：三角网、分区和路径的相关知识点 教学难点：分区和路径怎样在Coverage、Shapefiles和Geodatabase中进行不同的处理

25. 教学时间：2课时 教学方法：讲授法和多媒体教学法 本课程涉及的教学前沿

26. Georelational Data Model The georelational data model stores geometries and attributes separately in a split system: geometries (“geo”) in graphic files and attributes (“relational”) in a relational database. 该地理关系数据模型用两个独立系统分别存储空间和属性数据：用图形文件存储空间数据（“地理”），用关系数据库存储属性数据（“关系”）。

27. Figure 3.6 An example of the georelational data model, an ArcInfo coverage has two components: graphic files for spatial data and INFO files for attribute data. The label connects the two components.（地理关系数据模型的例子： an ArcInfo coverage 由两部分组成：图形文件存储空间数据， INFO 文件存储属性数据，两者间以标识码相连接）

28. The Coverage • The coverage supports three basic topological relationships: • Connectivity:Arcs connect to each other at nodes. • Area definition:An area is defined by a series of connected arcs. • Contiguity:Arcs have directions and left and right polygons. Coverage支持以下三种基本拓扑关系： ①连接性：弧段间通过节点彼此连接； ②面定义：由一系列相连的弧段定义面； ③邻接性：弧段有方向性，且有左多边形和右多边形。

29. Figure 3.7 The data structure of a point coverage.

30. Figure 3.8 The data structure of a line coverage.

31. Figure 3.9 The data structure of a polygon coverage.

32. The Shapefile • The shapefileis a standard, nontopological data format used in ESRI products. （在ESRI产品中采用的标准非拓扑数据格式称为Shapefile） • Although the shapefile treats a point as a pair of x-, y-coordinates, a line as a series of points, and a polygon as a series of line segments, no files describe the spatial relationships between these geometric objects. （尽管在Shapefile中，点是用一对x,y坐标，线是用系列的点，多边形用一系列的线来存储，但是没有描述几何对象空间关系的文件。 Shapefile 多边形对于共享边界实际上有重复弧段且可彼此重叠。 Shapefile 用几何学性质存储两个基本文件：以.shp为扩展名的文件存储要素几何特征；以.shx为扩展名的文件保留要素几何特征的空间索引）

33. Advantages of Nontopological Vector Data • Nontopological data such as shapefiles have two main advantages: • They can display more rapidly on the computer monitor than topology-based data. （非拓扑矢量数据能比拓扑数据更快速地在计算机屏幕上显示出来） • They are nonproprietary and interoperable, meaning that they can be used across different software packages (e.g., MapInfo can use shapefiles and ArcGIS can use MapInfo Interchange Format files). （非拓扑数据具有非专有性和互操作性，这意味着非拓扑数据可以在不同软件包之间通用）

34. Object-Based Data Model • The object-based data model treats spatial data as objects. It differs from the georelational data model in two important aspects.（基于对象数据模型将地理空间数据作为对象。基于对象的数据模型在两个重要方面不同于地理关系数据模型） • The object-based data model stores both the spatial and attribute data of spatial features in a single system. （基于对象数据模型把空间数据和属性数据存储在一个系统中。具有数据类型BLOB（binary large object)的空间数据以特定字段存储） • The object-based data model allows a spatial feature (object) to be associated with a set of properties and methods. （基于对象的数据模型允许一个空间要素（对象）与一系列属性和方法相联系。属性描述其对象的性质或特征。方法执行特定的操作）

35. Figure 3.10 The object-based data model stores each land use polygon in a record. The Shape field stores the spatial data of land use polygons. Other fields store attribute data such as Landuse_ID and Category.（基于对象数据模型中，每条记录存储一个土地利用多边形， Shape字段存储土地利用多边形的空间数据，其他字段存储属性数据，如土地利用-ID和类型。）

36. Classes and Class Relationships • A class is a set of objects with similar attributes. （类是一系列具有相似属性的对象） • Class relationships include association, aggregation, composition, type inheritance, and instantiation.（类和类之间的关系包括联合、聚合、合成、类继承和实例化）

37. Interface An interface represents a set of externally visible operations of an object. It allows the user to use the properties and methods of the object. （接口代表类或者对象的一系列外部可视化操作它允许用户使用对象的属性和方法） 基于对象技术是使用所谓的封装性将对象的属性和方法隐藏起来，使得只能通过预定义接口访问对象的技术。

38. Figure 3.11 A Feature object implements the IFeature interface. IFeature has access to the properties of Extent and Shape and the method of Delete. Object-oriented technology uses symbols to represent interface, property, and method. The symbols for the two properties are different in this case because Extent is a read-only property whereas Shape is a read and write (by reference) property.（一个Feature对象可以执行IFeature接口， IFeature可调用属性Extent和Shape以及方法Delete。面向对象技术用不同符号来表示接口、属性和方法。该例子中两种属性的符号不同，因为Extent是只读属性而Shape为可读写属性）

39. Figure 3.12 A Geodataset object supports IGeodataset and an Envelope object supports IEnvelope. See text for explanation of how to use the interfaces to derive the area extent of a feature layer.（ Geodataset对象支持IGeodataset， Envelope对象支持IEnvelope。参见注释栏解释如何用接口获得要素图层的区域范围）

40. The Geodatabase The geodatabase is part of ArcObjects, a collection of thousands of objects, properties, and methods that provides the foundation for ArcGIS Desktop. The geodatabase是基于对象矢量数据模型的一个例子，它是由ESRI公司开发的作为ArcGIS Desktop基础的 ArcObjects的一部分， ArcObjects是包含数千的对象、属性和方法的集合。

41. Data Structure in the Geodatabase • The geodatabase organizes vector data sets into feature classes and feature datasets • A feature class stores spatial data of the same geometry type. • A feature dataset stores feature classes that share the same coordinate system and area extent. Geodatabase将矢量数据集组织成要素类和要素数据集。 要素类存储具有相同空间几何类型的空间数据。 要素数据集存储具有相同坐标系和区域的要素类。

42. Figure 3.13 In a geodatabase, feature classes can be standalone feature classes or members of a feature dataset.

43. Topology Rules • The geodatabase defines topology as relationship rules and lets the user choose the rules, if any, to be implemented in a feature dataset. • The geodatabase offers 25 topology rules by feature type. Geodatabase将拓扑定义为关系规则，让用户选择规则，并在要素数据集中执行。 Geodatabase按要素类型提供25种拓扑规则。

44. Tables 3.1 Topology rules in the geodatabase data model

45. Advantages of the Geodatabase • The hierarchical structure of a geodatabase is useful for data organization and management. • The geodatabase, which is part of ArcObjects, can take advantage of object-oriented technology. • The geodatabase offers on-the-fly topology, applicable to features within a feature class or between two or more participating feature classes. • Thousands of objects, properties, and methods in ArcObjects are available for GIS users to develop customized applications. • ArcObjects provides a template for custom objects to be developed for different industries and applications.

46. 第3章 矢量数据模型（第3讲） 教学内容：3.5 复合要素的表示 教学目的： 1、让学生掌握复合要素的概念； 2、通过三角网、分区和路径等例子介绍让学生掌握复合要素 教学重点：三角网、分区和路径的相关知识点 教学难点：分区和路径怎样在Coverage、Shapefiles和Geodatabase中进行不同的处理

47. 教学时间：2课时 教学方法：讲授法和多媒体教学法 本课程涉及的教学前沿

48. Composite Features • Composite features refer to those spatial features that are better represented as composites of points, lines, and polygons. （复合要素是指以点、线和面合成应用而更好地表示的空间要素） • Composite features include TINs (triangulated irregular networks), regions, and routes. （复合要素包括三角网、分区和路径。

49. TIN A TIN approximates the terrain with a set of nonoverlapping triangles. （TIN把地表近似地描绘成一组互不重叠的三角面。每个三角面在TIN中都有一个恒定的倾斜度。平坦地区可用少量样点和大三角形来描绘，而高度变化大的地区则需要更密而较小的三角面来描绘。TIN通常用来地形制图和分析，特别是用3-D表达。） TIN的基本组成要素包括点、线和面。初始的TIN可以由高程点和等高线来构造，可以与线要素如河流、山脊线、道路，面要素如湖泊和水库相结合，以提高地表拟合精度。 一个完成的TIN由三种几何对象组成：三角形（区域）、点（节点）和线（边界）

50. Figure 3.14 A TIN uses a series of nonoverlapping triangles to approximate the terrain.（TIN模型把地表近似描绘成一组互不重叠的三角面）