1. Review of Projections and Coordinate Systems
Referencing Data to Real Locations

2. Coordinate Systems Geographic vs. Projected
Geographic Coordinate Systems (GCS)
Location measured from curved surface of the earth
Measurement units latitude and longitude
Degrees-minutes-seconds (DMS)
Decimal degrees (DD) or radians (rad)
Projected Coordinate Systems (PCS)
Flat surface
Units can be in meters, feet, inches
Distortions will occur, except for very fine scale maps

3. Geographic Coordinate System
Parallels - east to west – 0° at the Equator (0 °-90 °)
Meridians – north to south – 0° at the Prime Meridian (0 °-180 °)
Latitude and longitude are angular measurements made from the center of the earth to a point on the surface of the earth

4. Map Projection:
A map projection is a mathematical formula for representing the curved surface of the earth on a flat map.
wide variety of projections possible
each projection will create a different type of distortion

5. Distortions Distortions are inherent in maps distance area shape
The Earth is round, a map is flat
distance
area
shape
direction

6. Map Projections Types 14

7. Datums A reference frame for locating points on Earth’s surface
It consist of:
A spheroid (ellipsoid) with a spherical coordinate system and an origin.
A network of points that have been meticulously surveyed.

8. Modeling the Earth : spheroids, ellipsoid and datums!
North America Datums
NAD 27
Clarke 1866 spheroids
Meades Ranch, KS
Local Datum
NAD (National Geodetic Survey)
GRS80 (Geodetic Reference System) spheroid
Earth-centered
GPS compatible
WGS84 (National Imagery and Mapping Agency – National Geospatial – Intelligence Agency)
Additional parameters of model
Used in GPS
Why all the trouble to learn about datums?
meter shift between NAD 27 and NAD83/WGS 84!

9. Working with Coordinate Systems in ArcGIS
On-the-fly projection
“Define Projection” vs “Project”
Predefined Projections (provided by ArcGIS)
Projection File prj
Text file stores projection information
Data frame takes on the CS of the first data layer added to the project.

10. Map Projections Parameters
Standard Line – line of tangency - where the projection surface meets the globe
No distortion at this point – increase distortion moving away
Standard Parallel
Standard Meridian
More than one standard line possible
Central Line
Defines the center of the map projection
Central parallel - latitude of origin
Central meridian
Can be different from standard line
False Easting – x- coordinate value
False Northing – y- coordinate value 14

11. Commonly Used Map Projections in California
Universal Transverse Mercator (UTM)
California State System
(Teale) Albers Equal-Area Conic
State Plane Coordinate (SPC) System
Lambert conformal conic projection

12. Teale Albers Projection ( California)
AKA: CA State System,
CA Albers Equal Area
Projection Surface: Conical
Spatial Properties: Equal Area (Equivalent)
Projection Parameter
1st Standard Parallel: 34° 00’ 00’’
2nd Standard Parallel: 40° 30’ 00’’ Central Meridian: -120° 00’ 00’’
Central Parallel
Latitude of origin: 00° 00’ 00’’
False easting (meters): 0
False northing (meters): -4,000,000
Example of Coordinate:
X = -161,327 (meters)
Y = -149,199 (meters)

13. Universal Transverse Mercator (UTM)
60 zones
6o wide
Defined by central meridian (example: 120° W)
Preserves direction and small shapes (conformal projection).
Extent is from 84°N to 80 °S.
UTM coordinates are easily recognized by 6 digit for the x, and 7 digit for the y ( most of the time at latitudes of 15° and greater in the Northern Hemisphere)
80 S°
84 N°
Secant!

14. Universal Transverse Mercator (UTM)

15. UTM Zone 10 N and S Projection Surface: Cylindrical Central Meridian
Spatial Properties: Conformal, Shape and Direction
Projection Parameter
False Easting: 500, 000m
False Northing: 0 m
Central Meridian: -123°
Scale Factor:
Example of Coordinate in Monterey:
X = 602,585 (meters)
Y = 4,050,086 (meters)
Central Meridian
Value Decrease
Value Increase
Value Increase
False Easting 500,000 0m
0 m
10,000,000 m
80 S°
84 N°
Equator Origin
Value Increase 6°

16. UTM
Often found in military applications, and in datasets with global or national coverage
UTM system is secant with lines of scale 1 located on both sides of the central meridian, the projection is conformal, so small features appear with the correct shape and scale is the same in all directions. (Scale is at the central meridian and at most at the edges of the zones
Because there are effectively 60 different projections, maps will not fit together across a zone boundary.

17. Universal Transverse Mercator (UTM)

18. State Plane Coordinate System

19. State Plane Coordinate System (SPSC)
Although distortions of the UTM system are small, they are too great for accurate surveying
Plus zone boundaries follow arbitrary lines of longitude rather than jurisdictions.
Not a true map projection
Collection of different projections for every state in the US
Designed in the 1930s to provide a local reference system tied to a national datum.
Some states (depending on size and latitudinal extent) have multiple zones
Most USGS 7.5 minute maps indicate state plane coordinates (as well as UTM, and lat-long grid)

20. Cadasters and the US Public Land Survey System
The cadaster is defined as the map of land ownership in an area, maintained for the purposes of taxing land, or of creating a public record of ownership.
Parcels of land in a cadaster are often uniquely identified by number or by code.

21. The State Plane Coordinate System
East-West oriented States (or zones) use the Lambert Conformal Conic projection (ex. Tennesse)
North-South oriented States (or zones) use the Transverse Mercator projection (ex. Illinois)
One zone in Alaska uses Oblique Mercator
Based on the North American Datums: NAD27 and NAD83
Reference is in Eastings and Northings

22. SPCS

23. State Plane Coordinate System for California
AKA: Lambert Conformal Conic
Projection Surface: Conical
Spatial Properties: Shape and Distance
Projection Parameters
False Easting:
False Northing:
Central Meridian: -119 °
Standard Parallel_1: °
Standard Parallel_2: 37.25°
Latitude Of Origin: °
Example of Coordinate in Monterey:
X = 5,798,378 (feet)
Y = 2,135,524 (feet)

24. State Plane Zones for NAD 1927 and 1983