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Mapping Your Data 1
 

Mapping Your Data 1

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The first presentation for the mapping your data workshop. Much more informative, but not nearly as hands on. From an informational standpoint its better then 2, but from a workshop stand point ...

The first presentation for the mapping your data workshop. Much more informative, but not nearly as hands on. From an informational standpoint its better then 2, but from a workshop stand point it\'s much worse.

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Mapping Your Data 1 Mapping Your Data 1 Presentation Transcript

  • Mapping Your Data Christopher Martin [email_address]
  • Data Models
    • Two primary data models used when making maps
      • Raster Data
      • Vector Data
  • Raster Data
    • Consists of discrete cells (think graph paper)
      • Each cell has a discrete value
      • Occur in rows and columns
    • Examples
      • Images (all image types)
      • DEM
  • Vector Data
    • Each position is represented by coordinates
    • Coordinates are connected to form lines or polygons
    • Points, lines and polygons are then used to represent geographic features
    • Examples
      • Shapefile
  • Points, Lines, Polygons
  • Data Sources
    • US Census Bureau
      • Not just population data
      • Generalized Boundary Data
    • ESRI
      • TIGER/LINE
      • NED Data
      • FEMA Q3 Flood Data
    • USGS
      • SEAMLESS Distribution
  • Data Sources (cont’d)
    • NYS GIS Clearing House
      • Membership required
      • Wide variety of data
    • CUGIR
      • NYS and National data
      • Free, huge variety
    • CIGAR
      • Worldwide Elevation Data
    • Columbia University EDS
      • Electronic Data Service
  • Data Sources (cont’d)
    • Geography Network
      • Aggregates data from different providers
      • Online Map Server Available
  • Data Quality
    • Meta Data
      • Data about the data
      • All legitimate providers will provide this
      • Available for download or online viewing
  • Map Scale
    • The ratio between the distance on the map, and the distance in real life
      • ALWAYS expressed in terms of 1
      • Usually a ratio
        • E.g. 1:100000, 1:10000
      • Other scales are available
        • Visual scale is the second most common
  • Coordinate Systems
    • Two types of coordinate systems used in geography
      • Spherical (Latitude and Longitude)
        • Typically not used in ArcGIS
        • Always used in Google Earth
      • Rectangular
        • Predominantly used in Arc and GIS in general
        • UTM - Universal Transverse Mercator
        • State Plane
        • Other countries have their own.
  • Spherical Coordinate System
    • Based on meridians and parallels
    • Latitude (parallels)
      • Measured northward or southward from the equator to poles
      • Ranging 0-90 0 north or south
      • The measuring units are degrees, minutes, and seconds, 1 0 = 60’ and 1’=60”
      • The length of one degree latitude is similar everywhere, ≈ 111km/69miles
    • Longitude (meridians)
      • Measured eastward or westward from the Prime Meridian at Greenwich, England to the International Date Line
      • Ranging 0-180 0 east or west
      • The measuring units are the same as Latitude
      • Length of one degree longitude reduces toward poles
  • Rectangular Coordinate Systems
    • Convert the curved surface of the earth onto a flat surface
    • Standard cartesian coordinates, but different names
      • X is called “Easting”
      • Y is called “northing”
  • Universal Transverse Mercator
    • Based on the mercator map projection
    • Divides the world into 60 zones
      • Starts at 180 degrees longitude
      • Each zone is 6 degrees of longitude wide
      • Labeled 1-60 going eastward
    • And 20 Rows
      • Labeled C-X, skipping I and O
    • Intersection of Row and Zone is a Quadrangle
      • Usually referred to as “quad”
    • Measurement unit is meters
  • Universal Transverse Mercator
  • State Plane
    • Used exclusively in the United States
    • The US is divided into 120 zones
      • Follow state and county lines
    • Each state has its own map projection
      • North to South states use Mercator
      • East to West states use Lambert Conformal Conic
  • State Plane
  • So What?
  • Map Projections
    • A way to convert coordinates from spherical (earth) to flat (map)
      • Projections define how to to transform the spherical coordinates to flat ones
      • They are NOT map coordinates
    • Classified two ways
      • By the surface projected onto
      • By what gets distorted
  • Surfaces
    • Developable Surfaces
      • What kind of shape will we use?
      • It has to be 2D, and we need to be able to “unroll” it
      • The earth gets “wrapped” in the shape, and the surface is transferred to the 2D shape
    • Types
      • Cylindrical, Conic, Azimuthal
  • Cylindrical Projections
    • Mercator
    • Transverse Mercator
  • Azimuthal Projections
    • Top down view
      • Or Bottom Up
  • Conic Projections
    • Used to focus on a particular continent
      • Least amount of distortion for east-west direction
  • Distortion Projections
    • All maps distort
      • It’s inevitable
    • Projections can be grouped based on WHAT is distorted
      • Conformal - shapes are the same
      • Equal-Area - areas are the same
      • Equidistant - distances are the same*
  • Projection Example
  • Measuring Distortion
  • Comparisons of Projections
    • Map Projection Poster
  • Map Types
    • Thematic Maps
      • Not reference maps
    • Four main types
      • Choropleth Map
      • Proportional Map
      • Isarithmic Map (contour)
      • Dot Map
  • Choropleth Map
    • Shaded Areas
      • The “color” of the shade varies based on measurement of our variable
  • Isarithmic Map
    • Also known as Contour Maps
      • We draw lines to connect separate variables that have the same value
  • Proportional Symbol Map
    • Uses symbols
      • The size of the symbol varies according to the variable
  • Dot Density Map
    • Uses dots
      • Size is uniform, but the concentration represents changes in the variable
  • Cartograms
    • Are NOT maps
      • Area is not preserved
      • Area of the geographic regions varies by variable
    • Two primary types
      • Area
        • Area gets larger or smaller depending on the variable
      • Distance
        • Nodes or places can be closer or farther depending on realtive distance
  • Cartogram
  • File Formats
    • Shapefile
      • A collection of points, lines and polygons
      • Tabular data values assocated with each
    • DEM
      • Raster data, each cell represents elevation
      • Comes in different resolutions
  • Getting to Know ArcGIS
    • ArcMap
      • Your main tool. Handles map layout, projection, data classification, analysis
    • ArcCatalog
      • Asset management program. Maps drives of data for easy access, displays meta data, manages database connections
    • ArcView
      • Older version of ArcMap.
    • ArcScene
      • 3D rendering
  • Your friend, the Shapefile
    • A Misnomer
      • More the one file
        • Vectors in one file
        • Data in another
        • Index in another
        • Optionally a projection file