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 programming in Avenue language

Theme  Theme Point Line Area  Feature Individual item  Shapefile.shp.shx.dbf

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 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  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  Spherical to flat  Something preserved conformal = shape equivalent = size equidistant = scale azimuthal = direction  Projection surface cone, cylinder, plane

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  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)