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Projections and Coordinate Systems Chapter 2
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ArcView Structure Project View Theme Feature Project (.apr) ASCII text Location dependent!!!
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Documents View picture of the themes Table relational database (.dbf format) Chart bar, line, scatter, etc Layout the map Script programming in Avenue language
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Theme Theme Point Line Area Feature Individual item Shapefile.shp.shx.dbf
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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
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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
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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
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Projections Spherical to flat Something preserved conformal = shape equivalent = size equidistant = scale azimuthal = direction Projection surface cone, cylinder, plane
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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)
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Coordinate Systems Universal Transverse Mercator (UTM) Universal Polar Stereographic (UPS) State Plane Coordinate (SPC) Public Land Survey System (PLSS)
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UTM Universal Transverse Mercator 84°N and 80°S 60 zones 6° per zone Beginning at 180° W
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UPS Universal Polar Stereographic Polar areas 100,000-meter squares Similar to UTM
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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?
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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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