地理信息系统GIS课件11

,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,*,Chapter11,DataExploration,1,CHAPTER 11DATA EXPLORATION,Beginning of GIS analysis,What do you do with a database of dozens of layers and hundreds of attributes?,Data exploration allows you to examine trends, focus on relationships,Better understand data,Link maps, graphs, and tables,2,11.1 Data Exploration,Exploratory data analysis,Statistical analysis,Dynamic graphics,Data visualization,Finding Gestalt (finding patterns and properties in a data set),Posing queries,Making comparisons,3,11.1.1 Descriptive Statistics,Summarize values of a data set,Range,Median,Mean,Mode,Quantile analysis,Variance,Standard deviation,Z score,GIS packages offer descriptive statistics,4,11.1.2 Graphs,Visual display of data,Numerous possibilities,5,Figure 11.1,A line graph.,6,Figure 11.2,A histogram.,7,Figure 11.4,A scatterplot plotting % persons 18 years old in 2000 against % population change, 1990,2000. A weak positive relationship, with a correlation coefficient of 0.376, is present between the two variables.,8,Figure 11.5,A bubbleplot showing % population change, 1990,2000, along the x-axis; % persons under 18 years old in 2000 along the y-axis; and state population in 2000 by the bubble size.,9,Figure 11.6,A boxplot based on the % population change, 1990,2000, data set.,10,Figure 11.8,A QQ plot plotting % population change, 1990-2000 data value against the standardized value from a normal distribution.,11,Figure 11.9,A 3-D plot showing annual precipitation at 105 weather stations in Idaho. A north to south decreasing trend is apparent in the plot.,12,11.1.3 Dynamic Graphics,Graphs displayed in multiple and dynamically linked windows,Directly manipulate data points,Pose query in one window and get response in another window,Multiple linked windows optimal framework for posing queries,13,Brushing,Figure 11.10,The scatterplot on the left is dynamically linked to the map on the right. The,“,brushing,”,of two data points in the scatterplot highlights the corresponding states (Washington and New Mexico) on the map.,14,11.1.4 Data Exploration and GIS,Similar to exploratory data analysis in statistics, with two differences,In GIS it involves both spatial and attribute data,Media for data exploration in GIS involves maps and map features,15,11.2 Attribute Data Query,Search attribute data in order to retrieve a data subset,Selected subset can be examined in a table, displayed in charts, or linked to map features,Expressions which must be interpretable by the GIS,16,11.2.1 SQL (Structured Query Language),Data query language designed for relational databases,Designed by IBM in the 1970s and used by many commercial database management systems,17,SQL Structure (Syntax),select,from,where,select,keyword selects fields,from,selects tables,where,specifies the condition or criterion for data query,18,Figure 11.11,PIN relates the owner and parcel tables and allows use of SQL with both tables.,19,SQL Examples,Queries sale date of parcel coded P101,select,Parcel.Sale_date,from,Parcel,where,Parcel.PIN = P101,20,SQL Examples,Queries parcels larger than 2 acres that are zoned commercial,select,Parcel.PIN,from,Parcel,where,Parcel.Acres 2 AND Parcel.Zone_code = 2,21,SQL Examples,Queries sale date of parcel owned by Costello,select,Parcel.Sale_date,from,Parcel, Owner,where,Parcel.PIN = Owner.PIN AND Owner_name = Costello,This query involves two tables which must be joined first,22,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.2.2 Query Expressions,where,expression contains Boolean expressions and Boolean connectors,23,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,Boolean Expressions,Contains two operands and a logical operator,Parcel.PIN = P101,Operators include =, , =, ,24,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,Boolean Connectors,AND, OR, XOR, NOT,Used to connect two or more expressions,25,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,Figure 11.12,The shaded portion represents the complement of data subset A (top), the union of data subsets A and B (middle), and the intersection of A and B (bottom).,26,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.2.3 Type of Operation,Select a subset and divide the data into two groups,Those containing the selected records,Those containing the unselected records,Three types of operations,Add more records,Subtract records,Select smaller subset,27,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,Figure 11.13,Three types of operation may be performed on the subset of 40 records: add more records to the subset (+2), remove records from the subset (-5), or select a smaller subset (20).,28,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.2.4 Examples of Query Operations,Select a data subset and add more records to it,Select a data subset and switch selection,Select a data subset and select a smaller subset from it,29,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.2.5 Relational Database Query,Relational database often consists of many tables.,A relational database query selects overlapping records from all tables,Must understand the structure of the database,Can either join or relate the tables,30,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,Figure 11.14,The keys relating three dBASE files in the MUIR database and the soil attribute table.,31,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.3 Spatial Data Query,Retrieving data subset from a layer by working directly with features,Select features using cursor, graphic, or spatial relationship between features.,Results can be displayed on a map, linked to records in a table, displayed in charts, or saved as a new data set for further processing,32,11.3.1 Feature Selection by Cursor,Pointing and selecting or by dragging a box around the map features,33,11.3.2 Feature Selection by Graphic,Uses a graphic, such as a circle, box, line or polygon to select features that fall inside or are intersected by the graphic,Examples: selecting restaurants within a one-mile radius of a hotel, selecting land parcels that intersect a proposed highway, or finding owners of land parcels within a proposed nature reserve,34,Figure 11.15,Select features by a circle centered at Sun Valley.,35,11.3.3 Feature Selection by Spatial Relationship,Select features based on their spatial relationship to other features,In same layer or in different layers,Containment, intersect, proximity,36,Containment,Select features that fall completely within features for selection,Schools within a particular county, state parks within a particular state,37,Intersect,Select features that intersect other features,Selecting land parcels that intersect a proposed road, urban areas that intersect a fault line,38,Proximity,Select features within a specified distance of other features,State parks within ten miles of an interstate highway,Adjacency - when features to be selected and selection features share common boundary,39,11.3.4 Combining Attributes and Spatial Data Queries,When data exploration requires both attribute and spatial query,Gas stations within one mile of freeway exits and have an annual revenue exceeding $2 million,40,11.4 Raster Data Query,Concept and some methods same as for vector data query,Practical differences,41,11.4.1 Query by Cell Value,Operand is raster itself rather than a field, as in vector query,Boolean statement to separate cells that satisfy the query statement from those that do not,42,Figure 11.16,Raster data query: slope = 2 and aspect = 1. Selected cells are coded 1 and others 0 in the output raster.,43,Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.,11.4.2 Query by Select Features,Query by using feature such as points, circles, boxes, or polygons,44,11.5 Geographic Visualization,Cartographic visualization,Using maps to process visual information,Data classification, spatial aggregation, map comparison,45,11.5.1 Data Classification,Groups based on statistics,46,Figure 11.17,Two classification schemes: above or below the national average (a), and mean and standard deviation (SD) (b).,47,11.5.2 Spatial Aggregation,Groups data spatially,48,Figure 11.18,Two levels of spatial aggregation: by state (a), and by region (b).,49,11.5.3 Map Comparison,Compare data from different layers to examine relationships,50,Figure 11.19,An example of map comparison. Deer relocations tend to be concentrated along the clear-cut/old forest edge.,51,Other Options,Place all layers on a screen and view them one at at time,Use set of adjacent views,Use map symbols to show multiple data sets,52,Figure 11.20,A bivariate map: (1) rate of unemployment in 1997, either above or below the national average, and (2) rate of income change, 1996,1998, either above or below the national average.,53,