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Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques

Introduction to GIS. Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques. By Brian Voigt University of Vermont Thanks are due to Dr Troy and Dr Zhou, upon whose lecture much of this material is based. Introduction to GIS. 1. Vector Data Model. Introduction to GIS.

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Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques

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  1. Introduction to GIS Lecture 4: An Introduction to the Vector Data Model and Map Layout Techniques By Brian Voigt University of Vermont Thanks are due to Dr Troy and Dr Zhou, upon whose lecture much of this material is based.

  2. Introduction to GIS 1. Vector Data Model

  3. Introduction to GIS Reviewing Vector Data Types • Three basic “feature” or “object” types • Point • Arc • Polygon • A layer holds a single feature type

  4. Introduction to GIS Reviewing Vector Data Types • Attribute table • Attribute types • Nominal attributes: descriptive information • Ordinal attributes: rank order or scale • Interval/ratio attributes: numeric items, order, magnitude of difference

  5. Introduction to GIS Point Feature • A point layer: a collection of records with (x,y) coordinates 6 2 3,6 5 3 5,5 4 3 4 6,3 2 1 2,2 1 10 4,1 0 0 1 2 3 4 5 6 Image modified from ESRI Arc Info electronic help

  6. Introduction to GIS Line (Arc) Feature • One or several line segments define an arc (straight or curved) • 2 points define a line segment • Line endpoints are nodes; angle points are vertices (sing. vertex) • Arcs meet at nodes • Feature is the ARC, not the line segments • Feature has length but not area Vertices Line segment Node Node Image modified from ESRI Arc Info electronic help

  7. Introduction to GIS Line (Arc) Feature • Each point has a unique location

  8. Introduction to GIS 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 Lines (Arcs) Points

  9. Introduction to GIS Topology • Definition1:Explicit encoding of spatial relationships between objects: the spatial location of each point, line and polygon is defined in relation to each other • Definition2:Topology is a collection of rules and relationships that enables the geodatabase to more accurately model geometric relationships found in the world.

  10. Introduction to GIS Why Topology • Two major purposes • Allows for powerful analysis tools • Quality control mechanism

  11. Introduction to GIS Types of Vector Topology • Arc-node topology • Polygon topology • Route topology • Region topology

  12. Arc-node List Direction Introduction to GIS Arc-node & Node Topology • Connectivity analysis Arc-node Topology Image source: ESRI Arc Info electronic help

  13. Polygon-arc List The order does matter! Introduction to GIS Polygon-arcTopology Polygon-arc Topology Image source: ESRI Arc Info electronic help

  14. External polygon Introduction to GIS Polygon-arcTopology • Adjacency Image source: ESRI Arc Info electronic help

  15. Introduction to GIS Route Topology • Define paths based on series of arcs Image source: ESRI Arc Info electronic help

  16. Introduction to GIS Quality control and topology • Ensuring “logical consistency” • Define complex and nuanced rules governing spatial relationships of features • Data quality • Single layer quality control • Mutli-Layer quality control

  17. overshoot undershoot Introduction to GIS Quality control and topology • Single layer quality control Dangles sliver polygon does not share a border

  18. Introduction to GIS Quality control and topology • Multi-Layer quality control: Defining spatial rules between layers • Polygon rules: e.g. Must Be Covered by Feature Class of • Line rules: e.g. Must not Self Intersect • Point rules: e.g. Must be Properly Inside Polygons • ArcCatalog includes new tools for defining and validating topology rules (Book:Building a geodatabase)

  19. Introduction to GIS Topology rules: Example • 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

  20. Introduction to GIS Spaghetti Data Model • Collections of line segments and points • Only stores features’ coordinates • No real connection, topology or relationships Non-topological data model • Not for spatial analysis • Generally come from CAD files or digitizing • Can “clean” these data, using user-defined tolerances

  21. Introduction to GIS 2. Map Layouts and Cartographic Representation

  22. Introduction to GIS Map Composition X Map? Map Elements?

  23. Title Legend Neatline Data frame North arrow Scale bar Notes Introduction to GIS Map Composition

  24. Introduction to GIS Layouts Create a map for layout in ArcMap Layout view View>>Layout view.

  25. Introduction to GIS Map Compilation • Geographic features • Other map elements • Legend • Title • North arrow • Scale bar • Author • Neatline • Source of data • Other objects…

  26. Map Layout: Map Legend

  27. Map Layout: Map Legend Insert Legend Title

  28. Give a title, e.g. land use … but not “legend”! Symbol editing Introduction to GIS Legends are edited in the Legends property window: Accessed by double clicking a legend. Layouts

  29. Style Symbol Introduction to GIS Legend editing: Items Layouts Items

  30. Layouts Editing legend item style

  31. Introduction to GIS Editing legend frame Layouts Frame

  32. Introduction to GIS Editing legend size and position Layouts Size & Position

  33. Map Layout: North Arrows

  34. Map Layout: Scale Bar

  35. Introduction to GIS Layouts: data frame • Create a new view or “data frame” in ArcMap

  36. Introduction to GIS ArcMap: data frame • More than one frame can be shown in layout view Frame 1 Frame 2

  37. Data Frames: Context

  38. Data Frames: Inset maps

  39. Introduction to GIS Layouts: data frame Access and edit data frame properties

  40. Introduction to GIS • Mxd files are project files • Save your layout • All other preferences • Data is not included • With an extension .mxd MXD Files • File >> Save (As)

  41. Introduction to GIS • Save symbology and settings • Primarily for saving legend settings • Opening a layer file will open the data layer with all the preferences saved • With an extension .lyr Layer Files

  42. Introduction to GIS • Use layer files when you have lots of non-numeric categories Layer Files

  43. Introduction to GIS Create a layer file in ArcMap (also in ArcCatalog) Layer Files

  44. Introduction to GIS Import a layer file’s symbology in properties Layer Files

  45. Introduction to GIS • Save symbology and settings AND the data! • With file extension .lpk Layer Package Files

  46. Introduction to GIS Double-click the file to open in ArcMap or ArcCatalog Layer Package Files

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