1Introduction to Geographic Information SystemsI. Basic TerminologyA. Geographic Information Systems (GIS)1. Preliminary Ideasa. maps = models of the Earth(1) Traditional maps - paper drawings / models of the Earthb. map distribution = spatial distributionc. computers + digital informationd. computer assisted cartography (CAC) - digital mapse. computer assisted drafting (CAD) - digital drawings2. Definitiona. Computerized data input system that collects and processes spatial mapdatab. A data storage and retrieval system that organizes spatial data (database)c. A data manipulation and analysis system (mathematical and statisticaltasks)d. Report subsystem (graphic output = digital map, database tables)GIS = "capture, store, query, analyze, and display geographic data"B. Other Terminology1. Cartographic process - data collection and map compilation2. Map Featuresa. pointsb. lines(1) straight line segments - between two points(2) polylines - multiple segmented linesc. polygons - lines that enclose areas3. Map Layersa. layers of spatial data that form "tracing overlays" on top of one another(1) e.g. geology, vegetation, buildings, soil, etc.b. examples of layers or themes or coverages for any given map region(1) topography(2) geology(3) population density(4) roads(5) streams(6) vegetation(7) soils.... etc.4. Examples of Digital Data Sourcesa. Digital Line Graphs (DLG) - b. Digital Elevation Models (DEM) - grid data over space, eg. elevationc. Digital Photoquadrangles25. Example GIS measurements from dataa. line lengthsb. polygon perimetersc. polygon areasd. spatial density (e.g. housing density per square mile)e. frequency (the number of occurrences)f. map vs. ground distancesg. angles between lines6. LIS = land information systems7. GPS = global positioning systems - satellite-based location system8. Geodesy - measurement and mapping of the Earth's surfacea. Geodetic framework - position and elevation of points on the earth'ssurfaceII. Introduction to Spatial DataA. Spatial Coordinate System1. Longitude and Latitudea. Angular coordinate system relative to the Equator and Poles2. UTM = Universal Transmercator (northings and eastings in meters)a. Linear cartesian coordinate system relative to North-South and East-Westbaselines- measured in meters3. State Plane = "State Plane" (northings and eastings in feet)a. Linear cartesian coordinate system relative to North-South and East-Westbaselines- measured in feet4. Map Projectiona. Problem: the Earth is 3-D and spherical while paper maps and computerscreens are 2-D(1) How to project a 3-D object to a 2-D surface?b. Multiple map layers must be in the same projection if they are toappropriately line-up in space(1) e.g. can't overlay a geologic map in State Plane ontop of a soilmap in Lat-LonB. Types of Spatial Data1. Discrete Features - isolated map entities that are not connecteda. e.g. a water well = discrete point featureb. e.g. a road = discrete polyline feature2. Continuous Features - spatially distributed data across the mapa. e.g. rainfall / precipitation, bedrock geology, topography / elevation3. Map Featuresa. points, lines, polygons4. Feature Attributesa. data attached to points, lines, polygons(1) e.g. a point rainfall collection station could have an average annualprecipitation attribute attached to it.3C. Data Models1. Vector data model - points and their x,y map coordinates are used to createpoint, line, and polygon featuresa. Topological Vector Data - an expression of the spatial relationshipsbetween map features(1) e.g. vector points define a line with a start point, end point, leftside, and right sideb. Non-Topological Data - map features that do not have topologyassociated with themc. ESRI GIS Software Terms(1) Coverage = topological vector map data(2) Shapefile = non-topological vector map data2. Raster data model - rectangular grid cells are used to represent spatial featuresa. e.g. rainfall amounts in a watershedD. Attribute Data1. attribute data - data that describe the characteristics of spatial featuresa. e.g. a line that represents a road is attributed with the route number andtype of highway (2 lane, interstate, etc.)2. Managing Attribute Dataa. Georelational database - a collection of tables that are related to oneanother by common index attributes(1) functions: search, data retrieval, data editing, creation of tabularreports(2) Linking Tables - tables linked to one another by common attributesor identificationIII. GIS OperationsA. Spatial Data Input1. Create Database2. Digitize map features in relation to a map projection and coordinate system3. Digitizing - process of capturing spatial data on the computera. Digitizing tabletb. On-Screen Digitizing - "heads up" digitizingc. calibrating the digital feature with real-world geographic coordinates4. GPS as a tool for capturing spatial dataB. Attribute Data Management1. Using georelational database editor to enter attribute data to map features2. Database Tables (table = cells in rows and columns)a. Columns = Fieldsb. Rows = Records3. Key Fieldsa. Columns of data that can be used to link multiple tables togetherC. Data Display1. Digital Map / Cartographic Display2. Tabular Data Display4D. Data Exploration1. data-centered query and analysisa. query = asking a question of the data2. Identify general trends, distribution, and relationships between dataE. Data Analysis1. mathematical and statistical operations on spatial dataa. e.g. measure land slope from an elevation modelb. measure areas of bedrock geology polygons2. Spatial Interpolationa. Using discrete control points to estimate a continuous distributon of data(1) e.g. contouring elevation data to make a topographic mapb. GeostatisticsF. GIS Modeling / Spatial Modeling1. Using a given data set to model changes in spatial trends through time andspace2. Using existing data to create new dataIV. GIS and Spatial Database FunctionsA. Purpose: to use map feature to call and retrieve data about a given area or map object.B. Database Query1. Asking questions about attributes in a spatial database2. Geographic searching is critical to GIS database queriesC. Examples of spatial database queries that can be accomplished with GIS1. Find all homes in the city of Portland that have the following attributes: they arelocated within 50 ft of a fire hydrant, are painted red, are situated within 500 feetof an active fault zone, and have median household incomes of greater than$50,000.002. Find all map areas that are associated with
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