Lecture-6_Bb_1SlidePerPage - Spatial Analysis Spatial...

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Unformatted text preview: Spatial Analysis Spatial Analysis I What Is Spatial Analysis? Queries & Reasoning Reasoning Definitions De A method of analysis is spatial if: The _______ depend on the _______ of the objects being analyzed • move the objects and the results _______ OR • results are not _______ under relocation Spatial analysis requires both the attribute & location of objects GIS has been designed to store both Why Spatial Analysis Wh The Crux of GIS Provides the means of adding ______ to geographic data and of turning raw data into _______ information • Reveal patterns, trends, and anomalies that might otherwise be missed might otherwise be missed • Support decisions Why Spatial Analysis Wh Effective spatial analysis requires a collaboration collaboration between: The _______ & the intelligent _____ • Computer provides a check on human _______ by helping in situations where the eye might deceive deceive The The Snow Map Dr. John Snow Snow and his study on on the causes of cholera outbreak outbreak in the Soho district, district, London, 1854 www.jsi.com The Snow Map In 1854, it was commonly believed that Cholera was an airborne disease Snow noticed that the outbreak appeared to be centered on a public drinking water pump in Broad Street Hypothesis: Cholera was transmitted through the drinking of polluted water Support evidence: When the water supply was cut off, the outbreak subsided. The The Snow Map Provides a classic example of the use of examp _______ _______ to draw _______ (Spatial _______ (Spatial Analysis) Analysis) But it is possible that it is possible that the same pattern could arise from an airborne contagion contagion • If the original carrier lived in the center of the outbreak, airbornbe contagion may lead airbornbe contagion may lead to similar pattern The The Snow Map GIS could be used to identify the cause of identify the cause of the the pattern: A time series would reveal _______ and _______ deaths occurred. • If the contagion was airborne then deaths would expand ___________. • However, if contagion was in if in the water, deaths would occur more __________, depending upon the order in which people drank water from the th contaminated pump Where’s Where’s Osama? Dr. Thomas Gillespie, UCLA UCLA Geography Professor, employs Spatial Analysis to hypothesize the whereabouts of Osama Bin Laden. Where’s Where’s Osama? Dr. Thomas Gillespie UCLA Geography Professor employs Spatial Analysis to hypothesize the whereabouts of Osama Bin Laden. Types of Spatial Analysis Spatial Analysis Categories ______________ ______________ ______________ ______________ ______________ ______________ Queries and Reasoning Ask simple _________ of the GIS NO _______ is made to the original data New data is ____ produced A GIS can respond to user queries by GIS presenting data in different ________ and allowing the user to interact with and allowing the user to interact with them them These ______ are usually _______ are usually • Linking views is one important technique of exploratory spatial data analysis (ESDA) – ESDA allows users to gain insight by viewing and interacting with data in different ways A Catalog View (ArcCatalog) Left window exposes the window exposes the organization structures of folders, databases, and files The right window provides The right window provides more detailed information. For example, the data holdings of a workspace… …or a ‘preview’ of the geometry and attributes… …or a view of the Metadata The Map View (ArcMap) A user can interact with a user can interact with map view: To find the coordinates of objects (features) objects (features) To identify objects and query their attributes To search for objects meeting specified spatial criteria The Map View (ArcMap) Identify Simply identify the cell value at clicked identify the cell value at clicked location, but also give the number of cells with such a value in the grid. The Table View (ArcMap) Attributes are displayed in the form of a table, linked to a map view. When objects are selected in the table, they are automatically highlighted in the map view, and vice versa. versa. The table view can be used to answer simple queries about the attributes of a object. Query by Attributes & SQL SQL Structured Query Language • pronounced SEQUEL • Developed by IBM in 1970s Now de facto standard for accessing relational databases SQL is embedded in the _____ of _________ and _________ Simple SELECT SQL SQ Query from one table _______ <*> < attribute1, attribute2 …> _______ aTable _______ _______ <conditions> Conditions are boolean expressions Expressions evaluated to TRUE or FALSE Example 1 _______ name _______ tabGrade _______ grade = ‘B’ Result: Lin Lin Mark name grade Lin B David B+ Mark B Jane A Jon A- tabGrade Simple SELECT SQL SQ Combining two or more tables enables a single query of those multiple tables Considerably more powerful name grade name SSN name grade SSN Lin B Lin 112 Lin B 112 David B+ David 234 David B+ 234 Mark B Mark 235 Mark B 235 Jane A Jane 567 Jane A 567 Jon A- Jon 999 Jon A- 999 tabGrade tabStu tabGrade_Stu Q: For students with B grade, find their names and SSN? Select name, SSN from tabGrade_Stu where grade = ‘B’ Combining Tables: Relates & Joins Combinin _______ Logically link two tables through their key attributes _______ Merge the two tables into one according to key attributes • The output can be saved in a physical data file Combining Tables: Relates & Joins Combinin road rd-type Join/Relate to a layer in ArcMap Join/Relate to a layer in ArcMap Conditional Expressions Conditional A Conditional Expression is usually composed composed of A _______ _______ A _______, Connected by _______ _______ : _______ _______ =, >, >=, <, <= e.g. "AREA" > 1500 "AREA" 1500 “POP1990" <= 300000 Combining Conditional Expressions Combinin Complex query conditions can be built by using: AND OR NOT and other operators These may be depicted with Venn Diagrams Venn Diagrams… Combining Conditional Expressions Combinin AND The condition is satisfied (_____) if _______ expressions are TRUE Records that match both expressions will be selected • e.g. "AREA" > 1,500 AND “POP1990" > 300,000 • Spatial equivalent is ‘Intersect’ (see next week’s notes) Combining Conditional Expressions Combinin OR The condition is TRUE if _______ expression is TRUE Records that match at least one expression will be chosen • e.g. [RAINFALL] < 20 OR [SLOPE] > 35 • Spatial equivalent is ‘Union’ (see next week’s notes) Combining Conditional Expressions Combinin NOT The condition is TRUE if the expression after NOT is _______ All Records that do not match the expression after NOT will be selected • e.g. NOT "STATE_NAME" = 'Colorado' • Spatial equivalent is ‘Erase’ (see next week’s notes) Combining Conditional Expressions Combinin NOT combined with AND/OR e.g. [SUB_REGION] = 'New England' AND NOT [STATE_NAME] = 'Maine' l Combining Conditional Expressions Combinin XOR The condition is TRUE if either of the expressions is _______ Records that match one, but not both, expressions will be chosen • e.g. [Favorite_NFL_Team] = ‘NY Jets’ OR [IQ] = ‘High' • Spatial equivalent is ‘Symmetrical Difference’ Attribute Query In ArcMap 1 2 3 4 Geometr Geometry Query In ArcMap Query by geography involves the _______ _______ between features between features Spatial Relations Equals – same geometries same geometries Disjoint – geometries do not share common point Touches – geometries intersect at common boundary Crosses – geometries cross Within– geometry within Contains – geometry completely contains Overlaps – geometries of the same th dimension overlap Geometr Geometry Query (Select by Location) 2 1 3 4 5 Creating a selection layer in ArcMap A ________ (Not a (Not __________) of the original layer Edits made to the made to the selection layer are made to the ______ layer If the source layer is _________, the selection layer will no longer be ______ As such, when __________________ satisfies your needs, employ the _______________ instead. This way, if your source data is moved, your subset way if your source data is moved your subset will still be _________ when the source is redefined. The layer/selection can be exported to a Shapefile/feature class ...
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