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 INFOSpatial 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)