1. Geographic Information Systems
Coordinate Systems

2. 1. Map Scale
A ratio between a distance on the map and the corresponding distance on the earth
The distance on the map is always expressed as one, e.g., 1 : 100,000
Common map scales
1 : 24,000
1: 100,000
1 : 250,000
1 : 1,000,000

3. Map Scale Small and large scale Which one is a larger map scale?
1 : 24,000 or 1 : 100,000
Spatial scales
Map scale (large vs. small)
Resolution (fine vs. coarse)
Extent (large vs. small)

4. 2. Coordinate Systems Basic elements of a coordinate system
an origin, then the
location of every
other point can be
stated in terms of
a defined direction and
a distance in the
direction

5. 2. Coordinate Systems Rectangular coordinate systems
Spherical coordinate systems
Geographic coordinate system
Rectangular coordinate systems
UTM (Universal Transverse Mercator)
State Plane

6. 2 (1) Spherical Coordinate Systems
Based on a perfect sphere
Geographic coordinate system
- great circles
small circles
- meridians
parallels
- Latitude
- Longitude
courtesy:

7. Latitude Measured northward or southward from the equator to poles
Ranging north or south
The measuring units are degrees, minutes, and seconds, 10 = 60’ and 1’=60”
The length of one degree latitude is similar everywhere, ≈ 111km/69miles

8. Longitude
Measured eastward or westward from the Prime Meridian at Greenwich, England to the International Date Line
Ranging east or west
The measuring units
Length of one degree longitude reduces toward poles

9. Latitude and Longitude
Lines of Longitude
(North/South - meridians)
900 latitude
Lines of Latitude
(East/West - parallels)
Central Parallel 00
Prime
Meridian 00
courtesy: Mary Ruvane,

10. Reading Latitude and Longitude
19050’ S: 19 degrees 50 minutes Latitude South
43050’ W: 43 degrees 50 minutes Longitude West
’ W

11. 2 (2) Rectangular Coordinate Systems
Also referred to as Planar, Cartesian, and Grid coordinate system
It converts Earth’s curved surface onto a flat map surface
The x value is given first and called easting, then the y value is given and called northing

12. 2 (2) (i) UTM Universal Transverse Mercator coordinate system
A rectangular coordinate
system for the WORLD
Gerardus Mercator ( )
Courtesy of the Library of Congress, Rare Book Division, Lessing J. Rosenwald Collection.

13. UTM Zones and Rows Measuring unit: meter
Map projection: Universal Transverse Mercator
Zones: north-south columns of 60 longitude wide, labeled 1 to 60 eastward beginning at the 1800 meridian
Rows: east-west rows of 80 latitude high, labeled from C to X (without I, O) beginning at 800 S latitude
Quadrilaterals

14. UTM Zones of the World
courtesy:

15. A UTM Zone We always use zones and rarely use rows
courtesy:

16. UTM Easting and Northing
Each of the 60 zones has its own central meridian
The central meridian of a zone is given the easting of 500,000m and the equator is given a northing value of 0 for the northern hemisphere
For southern hemisphere, the equator is given a northing value of 10,000,000m
671,000m Easting, 4,749,000m Northing

17. Calculate Your Own Zone
44003’ Latitude N, 71058’ Longitude W = Zone ?
courtesy:

18. 2 (2) (ii) State Plane Coordinate
A rectangular coordinate system for the UNITED STATES
Measuring unit: foot
Zones: The U.S. is divided into 120 zones. Zone boundaries follow state and county lines

19. State Plane

20. 2 (2) (ii) State Plane Coordinate
Projections: Each zone has its own projection system
- Transverse Mercator for states of N-S extent
- Lambert's conformal conic projection for states of E-W extent

21. State Plane
The central meridian of a zone is given 2,000,000ft False Easting
False origin: it is established in the south and west of the zone as 0, 0
False easting, and false northing
Zones may overlap    

22. Difference between Systems
UTM and many other coordinate systems are defined based on the geographic coordinate system

23. Difference between Systems
Try to use the rectangular systems as much as possible, and not to use geographic system for calculation
Remotely sensed imagery and digital elevation models routinely use UTM
Land record system routinely use State Plane
know how to convert between projections (will be discussed in the lab)

24. 3. Datum
Vertical datum: is the zero surface from which all elevations or heights are measured

25. Datum
Geodetic datum: are established to provide positional control that supports surveying and mapping projects covering large geographic areas, such as a country, a continent, or the whole world
North American Datum of 1927 (NAD27) North American Datum of 1983 (NAD83)
Coordinates change if datum changes: a control point in CA
On NAD83: ,
On NAD27: ,

26. 4. Map Projections
A means of converting coordinates on a curved surface to coordinates on a plane
Map projections vs. coordinate systems
- Map projections define how positions on the earth’s curved surface are transformed onto a flat map surface
- Coordinate systems superimposed on the surface to provide a referencing framework on which positions are measured

27. Map Projections A classification of map projections
By conceptual methods
Cylindrical, Azimuthal, and Conic
By distortions
Conformal, Equal-area, Equidistant, and Azimuthal

28. Map Projections – by Methods
Cylindrical
1. Mercator 2. Transverse Mercator

29. Map Projections - by Methods
Azimuthal
     
Conic

30. Map Projections - by Distortions
Conformal projections  It retains shapes about a point
 Equal-area projections  It retains correct relative size
 Equidistant projections  It retains uniform scale in all directions but only from one or two points
 Azimuthal projections  It retains correct directions from one or two points

31. Map Projections - by Distortions
Conformal –
preserves shape
Equivalent -
preserves area
Equivalent -
preserves area
Compromise -
preserves neither
courtesy: Mary Ruvane,

32. Commonly Used Projections
Transverse Mercator: cylindrical conformal
 Lambert's conformal conic

33. Commonly Used Projections
UTM as a coordinate system
TM as a means of projection

34. Readings
Chapter 2

35. 3. Topographic Maps Planimetric maps
- Graphical representation of the shape and horizontal location of physical features of land and other physical entities.
Topographic maps
- identity elevation of the land in contour lines.
       

36. Topographic Maps A map series published by USGS
It is bound by parallels on the north and south, meridians on the east and west, 7.5’ span in either direction
The maps are created from aerial photos
The features are topography, vegetation, railroad, streams, roads, urban, etc.
Three coordinate systems are marked, geographical, UTM, and State Plane