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@2007 Austin Troy Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques Introduction to GIS By Brian Voigt University of Vermont Thanks are due to Dr Troy and Dr Zhou, upon whose lecture much of this material is based.
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@2007 Austin Troy 1. Vector Data Model Introduction to GIS
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@2007 Austin Troy Three basic “feature” or “object” types –Point –Arc –Polygon A layer holds a single feature type Reviewing Vector Data Types Introduction to GIS
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@2007 Austin Troy Attribute table Attribute types –Nominal attributes: descriptive information –Ordinal attributes: rank order or scale –Interval/ratio attributes: numeric items, order, magnitude of difference Reviewing Vector Data Types Introduction to GIS
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@2007 Austin Troy Point Feature A point layer: a collection of records with (x,y) coordinates Introduction to GIS Image modified from ESRI Arc Info electronic help 0123456 0 1 2 3 4 5 6 2,2 6,3 5,5 3,6 1 2 3 4 IDX,Y Coordinates 12,2 23,6 35,5 46,3 … 104,1 10
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@2007 Austin Troy Line (Arc) Feature Feature has length but not area Straight or curved Lines connect a set of vertices and nodes Feature is the ARC, not the line segments Arcs meet at nodes Introduction to GIS Image modified from ESRI Arc Info electronic help Line segment Node Vertices Node
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@2007 Austin Troy Line (Arc) Feature Each point has a unique location Introduction to GIS
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@2007 Austin Troy Polygon Feature Area of homogenous phenomena In a polygon layer, lines (arcs) define areas Closed region – first and last coordinate pairs are in the same location Line segments bound the polygon Introduction to GIS Lines (Arcs) Points
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@2007 Austin Troy Definition1: Explicit encoding of spatial relationships between objects: the spatial location of each point, line and polygon is defined in relation to each other Introduction to GIS Topology Definition2: Topology is a collection of rules and relationships that enables the geodatabase to more accurately model geometric relationships found in the world.
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@2007 Austin Troy Two major purposes Introduction to GIS Why Topology –Allows for powerful analysis tools – Quality control mechanism
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@2007 Austin Troy Arc-node topology Introduction to GIS Types of Vector Topology Polygon topology Route topology Region topology
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@2007 Austin Troy Connectivity analysis Introduction to GIS Arc-node & Node Topology Arc-node TopologyArc-node List Image source: ESRI Arc Info electronic help Direction
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@2007 Austin Troy Polygon-arc Topology Introduction to GIS Polygon-arc Topology Polygon-arc List The order does matter! Image source: ESRI Arc Info electronic help
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@2007 Austin Troy Adjacency Introduction to GIS Polygon-arc Topology External polygon Image source: ESRI Arc Info electronic help
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@2007 Austin Troy Introduction to GIS Route Topology Define paths based on series of arcs Image source: ESRI Arc Info electronic help
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@2007 Austin Troy
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Ensuring “logical consistency” –Define complex and nuanced rules governing spatial relationships of features Data quality –Single layer quality control –Mutli-Layer quality control Introduction to GIS Quality control and topology
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@2007 Austin Troy Say we have the following layers: parcels, sidewalks, right of way boundaries, building footprints, zoning Rules for spatial relationships –Lots must be enclosed polygons –Buildings must be entirely within a lot –Sidewalks must be outside a parcel polygon and entirely within the public right of way –Lots must fall entirely within a single zoning class –All lots must have access to a right of way Introduction to GIS Topology rules: Example
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@2007 Austin Troy Introduction to GIS sliver polygon does not share a border Single layer quality control Quality control and topology Dangles undershoot overshoot
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@2007 Austin Troy Introduction to GIS Multi-Layer quality control: Defining spatial rules between layers Quality control and topology – Polygon rules: e.g. Must Be Covered by Feature Class of ArcCatalog includes new tools for defining and validating topology rules (Book: Building a geodatabase) – Line rules: e.g. Must not Self Intersect – Point rules: e.g. Must be Properly Inside Polygons
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@2007 Austin Troy Spaghetti Data Model Non-topological data model Introduction to GIS Collections of line segments and points – Only stores features’ coordinates – No real connection, topology or relationships Not for spatial analysis Generally come from CAD files or digitizing Can “clean” these data, using user-defined tolerances
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@2007 Austin Troy 2. Map Layouts and Cartographic Representation Introduction to GIS
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@2007 Austin Troy Introduction to GIS Map Composition Map? X Map Elements?
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@2007 Austin Troy Introduction to GIS Title Legend Neatline North arrow Scale bar Notes Data frame Map Composition
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@2007 Austin Troy Layouts Create a map for layout in ArcMap Layout view View>>Layout view. Introduction to GIS
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@2007 Austin Troy Introduction to GIS Map Compilation Geographic features Other map elements – Legend – Title – North arrow – Scale bar – Author – Neatline – Source of data – Other objects…
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@2007 Austin Troy Layouts Introduction to GIS Give a title, e.g. land use Symbol editing Legends are edited in the Legends property window: Accessed by double clicking the legends.
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@2007 Austin Troy Layouts Introduction to GIS Legends editing: Items Item Style Symbol
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@2007 Austin Troy Layouts Introduction to GIS Legends editing: Frame Frame
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@2007 Austin Troy Layouts Introduction to GIS Legends editing: Size and position Size&Position
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@2007 Austin Troy ArcMap: data frame More than one frame can be shown in layout view Introduction to GIS Frame 1 Frame 2
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@2007 Austin Troy Layouts: data frame Create a new view or “data frame” in ArcMap Introduction to GIS
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@2007 Austin Troy Layouts: data frame Access and edit data frame properties Introduction to GIS
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@2007 Austin Troy MXD Files Introduction to GIS Mxd files are project files – Save your layout – All other preferences – Data is not included – With an extension.mxd File >> Save (As)
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@2007 Austin Troy Layer Files Introduction to GIS Save symbology and setting Primarily for saving legend setting Opening a layer file will open the data layer with all the preferences saved With an extension.lyr
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@2007 Austin Troy Layer Files Introduction to GIS Use layer files when you have lots of non-numeric categories
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@2007 Austin Troy Layer Files Introduction to GIS Create a layer file in ArcCatalog
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@2007 Austin Troy Layer Files Introduction to GIS Create a layer file in ArcMap
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@2007 Austin Troy Layer Files Introduction to GIS Import a layer file’s symbology in properties
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@2007 Austin Troy Layer Package Files Introduction to GIS Save symbology and settings AND the data! New at version 9.3.1 With an extension.lpk
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@2007 Austin Troy Layer Package Files Introduction to GIS Double-click the file to open in ArcMap or ArcCatalog
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