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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. Map Scale. Small and large scaleWhich one is a larger map scale? 1 : 24,000 or 1 : 100,000 Spatial scalesMap scale (large vs. small)Resolution (fine vs. coarse)Extent (large vs. small).
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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 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
7. Latitude Measured northward or southward from the equator to poles
Ranging 0-900 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 0-1800 east or west
The measuring units
Length of one degree longitude reduces toward poles
9. Latitude and Longitude courtesy: Mary Ruvane, http://ils.unc.edu/
10. Reading Latitude and Longitude 19050’ S: 19 degrees 50 minutes Latitude South
43050’ W: 43 degrees 50 minutes Longitude West
- 43050’ 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 (1512-1594)
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
15. A UTM Zone We always use zones
and rarely use rows
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
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
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: -117 12 57.75961, 34 01 43.77884
On NAD27: -117 12 54.61539, 34 01 43.72995
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
http://exchange.manifold.net
29. Map Projections - by Methods Azimuthal
30. Map Projections - by Methods http://egsc.usgs.gov/isb/pubs/MapProjections/projections.html
31. 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
32. Map Projections - by Distortions courtesy: Mary Ruvane, http://ils.unc.edu/
33. Commonly Used Projections Transverse Mercator: cylindrical conformal
Lambert's conformal conic
http://www.youtube.com/watch?v=b1xXTi1nFCo&feature=player_embedded
http://www.youtube.com/watch?v=AI36MWAH54s
34. Commonly Used Projections UTM as a coordinate system
TM as a means of projection
35. Readings Chapter 2
36. 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.
37. 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