Map Projection & Coordinate Systems
ArcView_module_6May 13, 1:30 PM
Outline Map Projection
Coordinate Systems
Setting a Map Projection in ArcView
Manipulating a Map Scale in ArcView
Map Projection Transforming three-dimensional
space onto a two-dimensional map
Map Projection
Curved Earth surface
Flat Map
Projection Types
Map Projection
Projections can be conceptually created by projecting from one geometric shape (a sphere) onto another (a cone, cylinder, or plane) Cylindrical: projects a sphere onto a
cylinder Conic: projects a sphere onto a cone Planar: projects a sphere onto a plane.
Cylindrical Projection
Good for displaying the world
Map Projection
Conic Projection
Good for displaying mid-latitude area such as U.S.
Map Projection
Planar Projection
Good for displaying hemisphere with one focus
Map Projection
Point or Line of Tangency
Point or line of zero distortion Projection distortion increases with
distance from the point of contact
Point for planar projection Line for conic/cylindrical projection
Map Projection
Point or Line of Tangency Cylindrical/Conic projections have
Standard parallel (line of tangency) Central meridian
Planar projections have Reference latitude (point of tangency) Central meridian
Map Projection
Coordinate Systems Defined based on a variety of geodetic d
atums, map projections, units, and reference systems
Coordinate Systems
Datum Used as a reference as in
surveying or mapping Based on the Spheroid (earth
model) Usually referred to as a keyword
(e.g. NAD83, WGS84)
Coordinate Systems
Datum
Coordinate Systems
Spherical vs Planar
Coordinate Systems
Spherical Planar
Dimension
3 2
Projection no yes
LatitudeLongitude
Global vs Local
Coordinate Systems
Global Local
feature Used globally Specific to local area
example GeographicUTM
State PlaneNational Grid
Choosing a Map Projection
depends on Which region to display (e.g. world, north po
le, equator, US) Resolution of the region Geometric properties of the region Purpose of using maps
such that the distortion can be minimized
Setting a Map Projection in ArcView
View Properties menu In ArcView. a view's map projection can
only be set if the map units of the spatial data it contains are decimal degrees
Setting a Map Projection in ArcView
Term definition Map units are the units which the spatial dat
a is stored in Map scale is the relationship between the di
mensions of a map and the dimensions of the Earth
Distance units are the units used by ArcView to report the result of operations (e.g. measurement (measure tool), dimension of shape (draw tool), dimension of selection box (select feature tool))
Manipulating a Map Scale in ArcView
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