map projections. putting a sphere on a flat surface messes up certain realities: ‐distance...
TRANSCRIPT
Map ProjectionsMap ProjectionsPutting a sphere on a flat surface messes up
certain realities:‐ Distance‐ Direction‐ Shape‐ Area
Each map keeps one or two things true (pros), but the others are not accurate (cons).
MercatorMercator
Pros:Direction
Cons:ShapeDistanceArea
Africa is actually 14 times larger than Greenland!
The Earth’s GridAny spot on Earth can be plotted with latitude
and longitude.• Lines of latitude run east-west
– “Lateral” means “side-to-side” (lateral pass)– Also called parallels
• Measured in degrees of N or S
• 0° latitude is the Equator
• 90° N is the North Pole
• 90° S is the South Pole
LongitudeLongitude
• Lines of longitude run north-south– “All lines of longitude are long”– Also called meridians
• Measured in degrees of E or W
• 0° longitude is the Prime Meridian– Runs through Greenwich, England, just outside
London
• 180° E/W is the International Date Line
The Earth’s Grid• A specific location uses N or S and W or E
for each coordinate pair
• Three ways to show coordinates:– Degrees, minutes, seconds:
30°, 15’, 45” N; 54°, 20’, 10” W• 1 degree = 60 minutes; 1 minute = 60 seconds
**Note: This is not in reference to time!
– Deg:min:sec : 30:15:45N, 54:20:10W
Three ways to show coordinates continued:
30:15:45N, 54:20:10W =– Decimals: 30.2625, -54. 336111
** (south and west are negative numbers)
• Found by dividing minutes/60 – i.e. 15 minutes = 15/60 = .25
• And then seconds/3600– i.e. 45 seconds = 45/3600 = .0125
• Add the two together: – .25 + .0125 = .2625
Latitude and LongitudeTogether, any point on Earth can be plotted on
a map
Use both coordinates together:
• Latitude, longitude40° N, 85° E 10° S, 15° W
• Walton: 33:59:20.663 N, 84:26:30.718 W
– This is the Front Office
Why Degrees, Minutes, Seconds?
• A circle is 360°– When computing various
angles, we base our measurements on degrees.
• i.e. Right angles are 90 °• An angle between 90° and
91° require requires minutes and seconds to find the specific angle.
• In 3D, we add the Z Axis, – which requires the
second degree measurement