Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lecture 3 spatial data modeling and management spatial data modeling and management 2017年5月22日 Spatial data structure Comparison of vector and raster Introduction to spatial database Data models in traditional database Data base for GIS 2 What is a data model ? The heart of any GIS is data model A data model is a set of constructions for describing and representing selected aspects of the real world in a computer There is no single type of GIS data model that is best for all circumstances 2017年5月22日 3 The role of a data model in GIS 2017年5月22日 4 GIS data models CAD 、geographical and image GIS data model Raster Data Model Vector Data Model Object Data Model 2017年5月22日 5 2017年5月22日 6 The CAD data model A CAD model focuses on feature drawing only ,so that it does not represent any kind of relationships between objects 2017年5月22日 7 Image data model 2017年5月22日 8 Difference between image data model and raster data model Image data do not have attribute table attached,so that they have only one attribute field. Raster data have attribute table that can be joint to other tables ,so that they can have multiple attribute field. application: image data---image processing raster data---spatial analysis and modeling 2017年5月22日 9 Vector data model Vector data model uses a set of coordinate and relationship to represent real world objects。 Geometry objects: Point:single point Line:string Area:closed loop other vector model: Triangulated Irregular Network:surface Region Dynamic segmentation:network 2017年5月22日 10 Vector data model:acquisition Surveying instruments(total station、GPS、 level,etc.) Digitize map Indirect methods: Rater to vector Data from spatial analysis 2017年5月22日 11 Vector data model:how to describe Storage and management of vector data Associate geometry data and attribute data Relationship of spatial objects 2017年5月22日 12 Vector data model cont. ( ) 2017年5月22日 Vector data model—the spaghetti structure Only to record position and attribute information of the spatial object,but not topological relationship Storage: Independence :spatial objects with its geometry information Point dictionary:coordinate storage is separated from its spatial objects Characters: no topological relationship ,so that only can be used to presentation and simple query of spatial object Exists data redundancy Can not keep consistency of the data,for the common part repeats storage Spatial analysis is more complicated Can not deal with the operation of polygon Appropriate applications: For the disadvantages that stated above,this data structure can be used to map and general query,but not for spatial analysis 13 Vector data model cont. ( ) 2017年5月22日 database ID Attribute Encoding point: ( x ,y ) line: ( x1 , y1 ) , (x2 , y2 ) , … , ( xn , yn ) area: ( x1 , y1 ) , (x2 , y2 ) , … , ( x1 , y1 ) Geometry point Point dictionary Encoding of spatial objects Sole Associate the attribute and position line area No X Y 1 11 22 2 33 44 … … … n 55 66 14 Vector data model:example of spaghetti structure polygon code coordinate A t123 1,2 3,4 … B 2 t124 No. of point coordinate 1 2 3 4 5 1,2 3,4 5,6 7,8 … 5,6 3 A 7 1 6 polygon code No. of point A B T123 t124 1,2,3,4,7,6,1 1,6,7,4,5,1 B 4 5 2017年5月22日 15 Vector data model cont. Vector data model:the topological structure Not only expressed the position and attribute of objects,but also relationship between objects Generally the topological relationship is conjunction The conjunction can be expressed in full expression and part expression Storage Directly storage Serial pointer ( ) Topological relationship and data share Conditions of using topological relationship 2017年5月22日 16 Vector data model cont. Vector data model : full expression M A1 A2 B1 N1 ( ) 2017年5月22日 A3 A6 N5 A4 Arc A5 B2 B3 B1 Area N2 N3 B2 B3 B4 A1 A2 A3 A4 A5 A6 A7 A8 Node N1 N2 N3 N4 N5 B4 A7 N4 A8 Polygon Arc Arc-node Arc from Node-arc Nod e Arc Arc Left Polygon-arc Arc-polygon to Right 17 Vector data model cont. Vector data model:part expression ( Using part table to describe topological relation System9:polygon-arc 、arc-node DIME:arc-node、arc-polygon The topological relationship is all in the above states in current GIS ) 2017年5月22日 18 Vector data model cont. Topological structure:how to describe in computer ( pointer polygon-arc、node-arc:it is not convenient directly storage for unequal length of record Example:POLYVRT TIGER Directly storage Arc/Info、GeoStar ) 2017年5月22日 19 Vector data model£¨cont.£© Topological structure:topological relationship and data share To keep data consistent 2017年5月22日 20 Vector data model cont. Topological relations:when to use topological structure Application Map and general query can not use topological structure Topological relation can be used to spatial analysis Objects can be described with topological relation Polygon object:polygon-arc、arc-polygon ( Network object:node-arc、arc-node ) 2017年5月22日 21 Vector data model:attribute Type type :what is the object? explanation information:different attribute with the same object description Encode Attribute table The item of attribute table depends on users 2017年5月22日 22 Map graphic data to attribute data linkage ID Encoding Coordinate ID Geodesic Geodesic Control-point Precision …… years organization grade ID Encoding Coordinate ID Grade ID Encoding ID owner point Spatial objects line area Material Breadth related line from、to、left、right Build time Management …… organization No. of boundary Build Build Building structure …… time organization area Type of object and attribute Encoding 2017年5月22日 Name of object Type of geometry Map color Map sign encoding Attribute 23 Triangulated irregular network 6 1 A 11 J K EDGES 5 B NODES 7 C adjacent 8 node# A B, K A 1, 6, 7 B A, C, L B 1, 7, 8 C B, D C 1, 2, 8 2 N I L M D 10 9 H G E D C, E, L D 2, 8, 9 E D, F E, G E F F 2, 3, 9 3, 4, 9 G F, H, M G 4, 9, 10 H G, I H 4, 5, 10 I H, J, N I 5, 10, 11 J I, K J 5, 6, 11 K A, J, N K 6, 7, 11 X-Y Coordinates Z Coordinates L L 7, 8, 9 node# node# M B, D, M G, L, N M 7, 9, 10 1 x1, y1 1 z1 N I, K, M N 7, 10, 11 2 x2, y2 2 z2 3 x3, y3 3 z3 ... ... ... ... 3 11 2017年5月22日 4 F coordinates x11, y11 11 z_value z11 24 Triangulated irregular network (cont.) 2017年5月22日 25 Dynamic segmentation Dynamic segmentation associates multiple sets of attributes to any portion of a linear feature Elements of dynamic segmentation : Route--- A route is a linear feature on which attributes are defined Measure---Each route is associated with a measurement system Events---Attributes associated with a route Advantage of dynamic segmentation • Define linear feature within a line coverage • Work with data in route-measure format • Apply attributes in route-measure to any part of a route without modifying underlying coordinate data Used to network analysis 2017年5月22日 26 Vector data structure:advantages and disadvantages Distinct location and implicit attribute Represent spatial relation with topological relationships Object-based operation with high accuracy and less data redundancy Difficult to combine with RS data High quality graphics 2017年5月22日 27 Raster data structure:contents Definition Divides the entire study area into a regular grid of cells,each cell contains a single value In rater data structure Point:pixel or cell Line:represented in cluster of adjacent pixel。 Area:pixel with same attribute that are congregated Data sources: Remote sense image Scanner Vector to raster Manual Raster coordinates Compress raster data Raster layers Rater data file structures Advantage and disadvantage of raster data structure 2017年5月22日 28 Area Line Point 2017年5月22日 29 Raster data structure:coordinate system and parameters Grid direction Resolution North-west coordinate (XWS,YWS) 2017年5月22日 X:Row Y:Col 30 Raster data structure:assign value to cell C A B 2017年5月22日 C Area importance A A AB 31 Raster data structure:compression 1 2 3 4 5 6 7 8 1 A A A A A A A R 2 A A A A A R R A 3 A A A A R A A A 4 A R R R A A A A 5 R A A A G G G A 6 A A G G G G G A 7 A A G G G G G A 8 A A A A G A A A Chain codes Number of start row and column,unit vector R: (1,5),3,2,2,3,3,2,3 7 4 0 3 1 Run-length codes Recording on row or column No. of row ,attribute, number of repeats 1, A, 4, R, 1, A, 4 SE NE 5 2 Block codes Quarter-tree codes NW 6 Rectangle Initial position, radius, value (1,1,3,A),(1,5,1,R),(1,6,2,A),¡ SW G GGGAGGAAGAAA 2017年5月22日 32 Hierarchy of the raster data structure Building Z Forest Soil relief Y X 2017年5月22日 33 File structure of the raster data structure Each cell is referenced directly , Map file Point X coordinate Each overlay is referenced directly, Map file Overly Point Y coordinate tile Overlay Z value Overlay values Next overlay values … Next point (X,Y) coordinate Each mapping unit is referenced directly Next point … … … Scale Mapping unit 1 Display symbol Attribute Next overlay X,Y Coordinates pairs … … Next mapping unit … 2017年5月22日 Lable Next overlay 34 Raster data structure:advantages and disadvantages Spatial object represented in discrete cell value Location is implicit and attribute is distinct Simple data structure and easy to combine with RS data Existing errors in geometry and attribute Difficult to build the relationship between spatial objects 2017年5月22日 35 c Geometry bias Ac distance: 7/4 (5) area: 7 (6) 5 a c 3 4 b a b Attribute bias 2017年5月22日 36 Comparison of vector and raster data model Vector model advantages: advantages: •It provides a more compact data structure than the raster model • It is a simple data structure •It provides efficient encoding of topology ,and as a result ,more efficient;implementation of operations that require topological information ,such as network analysis • High spatial variability is efficiently represented in a rater format •The vector model is better studies to supporting graphics that closely approximate hand-drawn maps disadvantages: 2017年5月22日 Raster model •It is a more complex data structure than a simple raster •Overlay operations are more difficult to implement •The representation of high spatial variability is inefficient •Manipulation and enhancement of digital images can not be efficiently done in the vector domain • Overlay operation are easily and efficiently implemented • The raster format is more or less required for efficient manipulation and enhancement of digital images disadvantages: • The raster data structure is less compact • Topological relationships are more difficult to represent • The output of graphic is less aesthetically pleasing because boundaries tend to have a blocky appearance rather than the smooth lines of hard-drawn maps.this can be overcome by using a very large numbers of cells ,but may result in unacceptable large files 37 Principles of selecting data models Object or fields Acceptable data Necessary accuracy of spatial objects location Topological relationships Type of spatial analysis Type of map 2017年5月22日 38 Spatial data management:spatial database data base A data base is defined as structured collection of information on a defined subject characters: Data is independent on application programs Relationship of data represent the connection of information in the real world Conventional data base management structures Hierarchy database structure Network database structure Relational database structure 2017年5月22日 39 Spatial data management:spatial database(cont.) Spatial database A spatial data base is a collection of geographical data and information on a defined area characters: Huge data quantity Location and attribute data combined Broad application areas Features of spatial data base spatiality Non-structured Spatial relationships Classification encoding Huge data quantity 2017年5月22日 40 Comparison of conventional database and spatial database Conventional database Spatial database continuous/correlation Discontinuous Non-correlation Continuous Spatial correlation Type of entity/spatial relationship Few Steady Many Unsteady Structured Equal Non-structured Unequal Record length Query and manipulation 2017年5月22日 Spatial operations words、numbers besides words and numbers 41 Spatial database management Hybrid model based on data file and relational database Extended model based on relational database Integrated model based on objectrelation database 2017年5月22日 42 Spatial data management based on file-relational database GIS interface ID Development language DBMS Graphic process attribute location Graphic interface early Graphic process database data file Graphic file database Attribute interface DBMS Attribute database Graphic file database Attribute database GIS interface Development language Graphic process Graphic file database 2017年5月22日 Database development language ODBC agreement DBMS Attribute database 43 Spatial data management based on relational database Attribute data (equal records) GIS interface Spatial data (unequal records) Relational tables Binary blocks DBMS Spatial database 2017年5月22日 44 Spatial data management based on object-relation database GIS interface Spatial data process DBMS Extend entities type Spatial database 2017年5月22日 45 GIS spatial data organization Arc/Info Concomitant control Work layer Study domain GIS project Spatial index Workspace 1 MGE GeoStar objects Logic layer Workspace2 MGE GeoStar Workspace n Attribute 2017年5月22日 Arc/Info 46 Spatial data index What is spatial data index Why is spatial data index needed in GIS How to build spatial data index 2017年5月22日 47 Spatial data index:object range index Collection of spatial objects Xmax 1 4 5 Ymin 6 3 4 Ymax Ymin 1 … … … … 2 … … … … 3 … … … … … … … … … Xmax>=XN OR Xmin<=XS OR XN Ymax>=YE OR Ymin<=YW No 2017年5月22日 Xmin Xmin XN XS Xmax Ymax 2 YW Retrieved windows ID YE XE<=Xmax,Xmin<=XN AND YW<=Ymax,Ymin<=YE YES YW 6 YE 3 2 XS 48 Spatial data index :index based on grid 1 2 3 1 2 3 4 1 2 3 1 3 7 5 2 4 9 10 4 1 2 8 6 3 P(2,1)=7 P(2,2)=8 P(2,3)=1 4 ID P 1 0 2 0 3 0 4 0 5 2 6 0 7 3 8 5 9 0 10 9 P(3,1)=4 P(3,2)=10 P(3,3)=6 4 Header pointer Link pointer 2017年5月22日 49 作业: 简述常用空间数据结构的特点; 简述空间数据库的特征,目前空间数据是如 何进行管理组织的? 简述栅格数据的压缩编码方案 试给出格网索引实现的原理(建立和检索) 2017年5月22日 50