What is Geography?Geographers’ Perspectives on the WorldIntroduction to MapsMap ElementsData SymbolizationThe Effect of ClassificationRepresenting the Real WorldBinary NotationTwo Fundamental Sorts of RepresentationsEntities  Data ObjectsThe Field ViewSpatial Data ModelsVector Data Model - ObjectsVector Data Model - TopologyRaster Data ModelCell Size & ResolutionRules for Assigning Cell ValuesVectorization and RasterizationVectorization - LinesRasterization - IssuesGeoreferencingGeodesy ReviewEllipticity of the EarthThe Earth as GeoidGeodetic DatumWhat is a Projection?Projections DistortThree Families of ProjectionsPreservation of PropertiesTissot’s IndicatrixCoordinate SystemsThe Geographic Coordinate SystemPlanar Coordinate SystemsPlanar Coordinate SystemsUniversal Transverse MercatorUniversal Transverse MercatorUniversal Transverse MercatorState Plane Coordinate SystemRepresenting Scale on MapsScale and Map ProjectionsMap Scale and Spatial ResolutionMaps and GIS - Scaling UpMaps and GIS - Scaling DownThe Two Types of Data in GISThe Role of DBMS in GISRelational Data ModelRelational JoinSpatial RelationsContains RelationTouches RelationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005What is Geography?•Geography is not just about city and country names•Geography is not just about population and growth•Geography is not just about rivers and mountainsGeography is a broad field that studies all sorts of phenomena on the Earth’s surface, including natural and human components, and these are termed human and physical geography.Geography is present in your everyday life: The air you breathe, the water you drink, the place where you live, the people you meetDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Geographers’ Perspectives on the World•Location matters•Real-world relationships•Horizontal connections between places•Importance of scale (both in time and space)David Tenenbaum – GEOG 070 – UNC-CH Spring 2005Introduction to MapsDefinition:•A graphic depiction on a flat medium of all or part of a geographic realm in which real world features have been replaced with symbols in their correct spatial location at a reduced scale.•To map is to transform information from one form to another --- Mathematicsmap•Earth surface Paper --- GeographyDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Map ElementsLegendScaleCreditsNorth ArrowPlace nameInsetGroundMap/Spatial DataNeat lineBorderTitleDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Data Symbolization•There are a number of characteristics of symbols that we can use of to make visual distinctions in thematic information (Jacques Bertin’s Visual Variables):•Size•Shape•Color Hue (color)•Color Value (intensity)•Texture•Orientation•ArrangementDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005The Effect of Classification• Four common ways to display continuous data in ArcView (i.e. these are options in the Legend Editor):– Equal Interval– Quantiles– Natural Breaks– Standard DeviationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Natural BreaksNatural BreaksQuantilesQuantilesEqual IntervalEqual IntervalStandard DeviationStandard DeviationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Representing the Real World•In a GIS, the representation of real world phenomena makes use of digital data formatsrepresentationEarth surface Digital dataDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Binary Notation•Everything is represented as 0s and 1s in a computer. These two-state forms correspond to yes/no, on/off, open/closedBinary Decimal1 digit 0, 1 1 bit 0,1,2,…92 digits 00, 01 2 bits 00, 01,…10, 11 97, 993 digits 000, 001 3 bits 000, 001,010, 011 002, 003,100, 101 …110, 111 998, 999One to one correspondenceDecimal Binary0 01 12 103 114 1005 1016 ?David Tenenbaum – GEOG 070 – UNC-CH Spring 2005Two Fundamental Sorts of Representations•Regardless of what phenomena of interest we chose to include in our geographic representation, we first must choose between a model that either•represents geography as discrete objectsOR•represents geography as fields•Most GIS approaches focus on the discrete object view, and we’ll look at it in greater detail, although we will look at field representations as wellDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Entities Æ Data Objects•In the discrete object view, we associate each and every entity we wish to represent with its own data object – a digital “building block” used in a data structure to represent an entitypointlinepolygon (area)(x,y)(x,y)(x,y)(x,y) (x,y)(x,y)(x,y)(x,y)(x,y)(x,y)David Tenenbaum – GEOG 070 – UNC-CH Spring 2005The Field View•In contrast to the discrete object view, which models the world in terms of entities, the field view approaches the world as consisting of continuous phenomena:The field view represents the real world as a finite number of variables, each one defined at every possible position (p.69 of the text)•This view is inherently problematic for digital representation, which necessarily has to discretize the world into some set of minimum unitsDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Spatial Data Models• Rasteruses individual cells in a matrix, or grid, format to represent real world entities• Vectoruses coordinates to store the shape of spatial data objectsDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Features in the real world are represented by objects that are chosen to approximate their shapeGeographic Primitives•Points–0 dimensional •Lines–1 dimensional•Polygons–2 dimensionalVector Data Model - ObjectsDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Topology defines spatial relationships. The arc-node data structure supports the following topological concepts:•Area definition: Arcs connect to surround an area, defining a polygon•Containment: Nodes (or arcs) can be found within a polygon•Connectivity: Arcs connect to each other at shared nodes•Contiguity: Arcs have a defined direction, and left and right sidesVector Data Model -