Projections and coordinate systems
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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

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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)


Projections and coordinate systems

UTM

  • Universal Transverse Mercator

  • 84°N and 80°S

  • 60 zones

  • 6° per zone

  • Beginning at 180° W


Projections and coordinate systems

UPS

  • Universal Polar Stereographic

  • Polar areas

  • 100,000-meter squares

  • Similar to UTM


Projections and coordinate systems

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?


Projections and coordinate systems

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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