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Projections and Coordinate Systems. Chapter 2. ArcView. Structure Project View Theme Feature Project (.apr) ASCII text Location dependent!!!. Documents. View picture of the themes Table relational database (.dbf format) Chart bar, line, scatter, etc Layout the map Script

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Projections and coordinate systems

Projections and Coordinate Systems

Chapter 2


Arcview
ArcView

  • Structure

    • Project

    • View

    • Theme

    • Feature

  • Project (.apr)

    • ASCII text

    • Location dependent!!!


Documents
Documents

  • View

    • picture of the themes

  • Table

    • relational database (.dbf format)

  • Chart

    • bar, line, scatter, etc

  • Layout

    • the map

  • Script

    • programming in Avenue language


Theme
Theme

  • Theme

    • Point

    • Line

    • Area

  • Feature

    • Individual item

  • Shapefile

    • .shp

    • .shx

    • .dbf


Arc info
Arc/Info

  • ARC and INFO

    Spatial and attribute information are separate

    • ARC is spatial information

    • INFO is attribute information

    • data is binary

      - must use tools to read


Coverage
Coverage

  • Coverage can be

    • point

    • arc

    • polygon

  • More complex

    • We will build up the expertise

    • representation of data

    • multiple components for each kind of coverage


Geographic grid
Geographic Grid

  • Meridians and parallels

  • Longitue and latitude

  • E-W and N-S

  • DMS=degree-minute-second

  • DD=decimal degrees

  • Convert D + M/60+S/3600 = DD


Projections
Projections

  • Spherical to flat

  • Something preserved

    • conformal = shape

    • equivalent = size

    • equidistant = scale

    • azimuthal = direction

  • Projection surface

    • cone, cylinder, plane


Datum
Datum

  • Spheroid or ellipsoid

  • North American Datum of 1927 (NAD27) and Clark 1866 (ground-measured)

  • North American Datum of 1983 (NAD83) and WGS84 or GRS80 (satellite-measured)


Coordinate systems
Coordinate Systems

  • Universal Transverse Mercator (UTM)

  • Universal Polar Stereographic (UPS)

  • State Plane Coordinate (SPC)

  • Public Land Survey System (PLSS)


UTM

  • Universal Transverse Mercator

  • 84°N and 80°S

  • 60 zones

  • 6° per zone

  • Beginning at 180° W


UPS

  • Universal Polar Stereographic

  • Polar areas

  • 100,000-meter squares

  • Similar to UTM


SPC

  • State Plane Coordinate

  • 1930s accuracy of 1/10,000 or less

  • State may have more than one zone

  • Shape of state changes N-S or E-W

  • Texas has how many?


PLSS

  • Public Land Survey System

  • Not in Texas

  • Mainly central and western states

  • 6 x 6 mile squares (townships)

  • 36 square mile parcels of 640 acres (sections)


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