1. Location, Location, Location

2. Geodesy
The study of the size and shape of the Earth.

3. The Earth is… 3000 BC Babalonians An oyster 600 BC Greeks Flat
500 BC a perfect shape A sphere
300 BC Circumference ~ 25,000 miles,
Dark ages Flat again
1492 Columbus A pear
1753 French Oblate ellipsoid
Spheriod
Geoid to describe the deviations from a spheriod

4. The Earth as a Geoid

5. Geographic Coordinate System
Parallels
Meridians
Great and Small Circles

6. Geographic Coordinate System
GCS uses a 3-D spherical
surface to define locations
on Earth.
GCS includes an angular unit
of measure, a prime meridian
and a datum.

7. Locating yourself on a Sphere
You need a frame of reference
That is the purpose of Latitude and Longitude
Defining these parameters:
Earth rotates on an imaginary axis ~ North and South Poles
Equator: is a great circle that lies equidistant between them.

8. Great Circles
..are imaginary circles of the surface of the earth who's plane passes through the center of the earth.
The circumference of the earth is 25,000 miles or 40,000 km
"Great" because it is the largest possible circle

9. Great Circles:
Cut the earth in half and each half is known as a hemisphere
Are the circumference of the earth
Provide the shortest routes of travel on the earth's surface.
** Planes travel in great circles.
** We were always taught a line is the shortest distance between two points - Not True.
Small circles: circles whose planes do not pass through the center of the earth.

10. Latitude
Latitude: is the angular distance north or south of the equator. (0 –90 degrees N or S)
1° of latitude = 40,000 km/ 360°
1 degree = 60 minutes
1 minute = 60 seconds 36°49'52" N
ArcView 3.x uses Decimal Degrees only
Sextant measures the angular distance between 2 points (sun & horizon)
**So it easy to determine latitude.

11. Longitude: Longitude: no natural reference point
In 1884 by International Agreement Greenwich England was the chosen starting point.
This is called the prime meridian or zero degrees and everything is east or west of that.
Longitude is the angular distance east or west from Greenwich, England
(0 – 180 degrees E or W)

12. Geographic Coordinate System
Longitude and Latitude
Degrees, minutes, seconds
1o latitude ~110.5 km (equator)
1o longitude = cosine of the latitude
1 minute of latitude ~1852 m

13. How to convert from DMS to DD
Example: 37°36’30”
Divide each value by the number of minutes or seconds in a degree
36 minutes = .60 degrees (36/60)
30 seconds = degree (30/3600)
Add it all up
37° = DD

14. The global grid:
Parallels: lines of latitude, only the equator is a great circle all other parallels are small circles (they never meet)
Meridians: these are line of longitude and when joined with its mate half way around the globe form great circles
* the distance between meridians will vary with latitude

15. How the Earth is Divided
Hemispheres: Northern, Southern, Eastern, Western

16. Time Zones
Solar noon: most towns used this, defined as when a vertical stake cast the shortest shadow.
By the 19th century transportation and communications (namely railroads and telegraph) connected towns and cities, the adopt of a standard time was necessary.

17. Time Zones (continued)
1884 at the International Meridian Conference 24 time zones were established.
Greenwich Mean Time (GMT) = Universal time = Zulu time
360°/24 = 15° for each time zone, however for convenience many time zones follow state and country lines.
International Date Line: where each new day begins 180th meridian
Chronometer

18. Time Zones