1. Map Projection & Coordinate Systems
ArcView_module_6
May 13, 1:30 PM

2. Outline Map Projection Coordinate Systems
Setting a Map Projection in ArcView
Manipulating a Map Scale in ArcView

3. Map Projection
Map Projection
Transforming three-dimensional space onto a two-dimensional map
Curved Earth surface
Flat Map

4. Map Projection
Projection Types
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.

5. Cylindrical Projection
Map Projection
Cylindrical Projection
Good for displaying the world

6. Conic Projection Map Projection
Good for displaying mid-latitude area such as U.S.

7. Planar Projection Map Projection
Good for displaying hemisphere with one focus

8. Point or Line of Tangency
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

9. Point or Line of Tangency
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)

10. Coordinate Systems
Coordinate Systems
Defined based on a variety of geodetic datums, map projections, units, and reference systems

11. Datum Used as a reference as in surveying or mapping
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)

12. Coordinate Systems
Datum

13. Spherical vs Planar Spherical Planar Dimension 3 2 Projection no yes
Coordinate Systems
Spherical vs Planar
Spherical
Planar
Dimension 3 2
Projection no
yes
Latitude
Longitude

14. Global vs Local Global Local feature Used globally
Coordinate Systems
Global vs Local
Global
Local
feature
Used globally
Specific to local area
example
Geographic
UTM
State Plane
National Grid

15. Choosing a Map Projection
Setting a Map Projection in ArcView
Choosing a Map Projection
depends on
Which region to display (e.g. world, north pole, equator, US)
Resolution of the region
Geometric properties of the region
Purpose of using maps
such that the distortion can be minimized

16. 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

17. Manipulating a Map Scale in ArcView
Term definition
Map units are the units which the spatial data is stored in
Map scale is the relationship between the dimensions 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))