What is Geography?Ten Big Questions that Geographers AnswerGeographers’ Perspectives on the WorldIntroduction to MapsMap ElementsData SymbolizationRepresenting the Real WorldBinary NotationBinary NotationBits and BytesASCII EncodingTwo Fundamental Sorts of RepresentationsEntities  Data ObjectsThe Field ViewSpatial Data ModelsVector Data Model - ObjectsVector Data Model - TopologyRaster Data ModelCell Size & ResolutionRules for Assigning Cell ValuesGeoreferencingShape of the EarthShape of the EarthShape of the EarthShape of the EarthWhat 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 MapsMap Scale and Spatial ResolutionThe Two Types of Data in GISAdvantages of Databases over FilesDisadvantages of Databases over FilesThe Role of DBMS in GISRelational Data ModelRelation Rules (Codd, 1970)Global Positioning System (GPS)GPS – Space Segment (Satellites)GPS – User Segment (Receivers)David Tenenbaum – GEOG 070 – UNC-CH Spring 2005•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 meetWhat is Geography?David Tenenbaum – GEOG 070 – UNC-CH Spring 20051. What makes places different from one another, and why is this important?2. Is there a deeply human need to organize space by creating arbitrary borders, boundaries, and districts?3. How to delineate space?4. Why do people, resources, and ideas move?5. How has the Earth been transformed by human action?6. What role will virtual systems play in learning about the world?7. How do we measure the immeasurable?8. What role has geographical skill played in the evolution of human civilization and what role can it play in predicting the future?9. How and why do sustainability and vulnerability change from place to place and over time?10. What is the nature of spatial thinking, reasoning, and abilities?Susan Cutter et al. Aug, 2002, The Professional Geographer, 54(3):305-317.Ten Big Questions that Geographers AnswerDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•Location matters•Real-world relationships•Horizontal connections between places•Importance of scale (both in time and space)Geographers’ Perspectives on the WorldDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Definition:•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 --- Mathematics•Earth surface Paper --- GeographymapIntroduction to MapsDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005• Most common elements include: – map/spatial data – title – legend – scale – north arrow – inset(s) – textual information– borders & neatlines – coordinate gridMap ElementsDavid 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 2005representationRepresenting the Real WorldEarth surface •In a GIS, the representation of real world phenomena makes use of digital data formatsDigital dataDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Binary 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, 999•Everything is represented as 0s and 1s in a computer. These two-state forms correspond to yes/no, on/off, open/closedOne to one correspondenceDecimal Binary0 01 12 103 114 1005 1016 ?Binary NotationDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005Binary NotationDecimal:72,479 = 70,000 = 7×1042,000 = 2 ×103400 = 4×10270 = 7×1019 = 9×1001001011021031042021222324Binary:1 0 1 0 01× 24+0 × 23+1 × 22+0 × 21 +0 × 20= 16 + 0 + 4 + 0 + 0 = 20Note: In binary1010+ 11010000David Tenenbaum – GEOG 070 – UNC-CH Spring 2005101110108 bits = 1 byte1024 bytes = 1 Kb1024 Kb = 1 Mb1024 Mb = 1 Gb1024 Gb = 1 Tb1024 Tb = 1 Pb1 bit = 1 binary digit1 byte = 8 bitsBits and BytesDavid Tenenbaum – GEOG 070 – UNC-CH Spring 2005•If computers store everything using 0s and 1s, then how are characters represented?•The ASCII (American Standard Code for Information Interchange) code assigns the numbers 0 through 127 to 128 characters, including upper and lower case alphabets plus various special characters, such as white space etc.•e.g. decimal 85 is assigned to represent upper case U. In binary, 01010101 = 85. Thus the computer represents U using 01010101.•Files which contain information encoded in ASCII are easily transferred and processed by different computers and programs. These are called “ASCII” or “text” files.ASCII EncodingDavid 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