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# Lecture3 latlongpost

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• 1. Announcements
• Review sessions today & Wednesday
• 4-4:45 pm, room 230
• 2.
• 3. Welcome to Earth You are here Inner/ Rocky Outer/Gaseous No longer a planet SUN
• 4.
• Aphelion: farthest position from Sun (July 4)
• Perihelion: closest position to Sun (Jan. 3)
Does this seem weird to you? Earth’s Elliptical Orbit This drawing is very misleading!
• 5. Earth’s Elliptical Orbit
• 6. The Earth is Round An Oblate Ellipsoid
• Imagine a slightly squished sphere
• Satellite observations show us that the Earth isn’t perfectly round…It’s flattened at the poles and bulging at the equator.
21 km difference
• 7. The Earth is Round An Oblate Ellipsoid
• In 1687, Newton predicted this distortion…
• As the Earth rotates, the equator moves faster than the poles.
• The outward force of Earth’s rotation produces a bulge in the equator.
• 8. The Geographic Grid System
• provides system (but not a flow system!) for locating places on the Earth’s surface
• divides Earth into imaginary circles parallel and perpendicular to axis of rotation
• 9.
• angular distance north or south of the equator
• equator = 0 º, poles = 90º
latitude = angle; parallel = line Latitude
• 10. Latitude The Oregon Boundary Dispute The 49 th Parallel The 42 nd Parallel Fifty-four Forty or Fight!
• 11.
• Angular distance east or west of a point on the Earth’s surface
• Prime Meridian = Greenwich, UK = 0 º
longitude = angle; meridian = line Longitude
• 12. Royal Observatory, Greenwich England Prime Meridian
• 13. 100 th Meridian Longitude Beyond the Hundredth Meridian Wallace Stegner
• 14. Measuring lat and long
• DMS units
• degrees ( º) , minutes ( ' ), seconds ( &quot; ), direction
• 60 minutes = 1 degree
• 60 seconds = 1 minute
• e.g., 41 º 27 ' 41 &quot; N
• Decimal units
• degrees in decimal format, direction
• e.g., 41.4614 ºN
• 15. Infrared Aerial Photo 200 m 37˚ 16’ 12” N 76˚ 42’ 42” W 2” 9”
• 16. Measuring lat and long
• Converting DMS units to Decimal Degrees
• 77 º 42 ' 25 &quot;
• 25 &quot; = (25 / 60)' = 0.4167'
• 77 º 42.4167 '
• 42.4167 ' = ( 42.4167 / 60)º = 0.7069º
• 77.7069 º
• “ Simple” formula (plug & chug)
• Dec. degrees = D º +((M ' +(S &quot; /60))/60)
• 17. Finding your position on the global coordinate system
• Which way is North?
Azimuth/Bearings: North = 0˚ or 360˚ East = 90˚ South = 180˚ West = 270˚
• 18.
• Option 1:
• Use a map
• 19.
• Option 2:
• Use a map (again)
• & take bearings
• 20.
• Taking Bearings
• 058˚ to Mt. Owens
Finding your position x Cape Point Mt. Owens x N 1 km 058 o
• 21.
• Taking Bearings
• 058˚ to Mt. Owens
• 327˚ to Cape Point
Finding your position x Cape Point Mt. Owens x N 1 km 327 o
• 22.
• Taking Bearings
• 058˚ to Mt. Owens
• 327˚ to Cape Point
• Need map & landmarks!
• 23. But how do you find yourself when land cannot be seen?
• 24. Finding your position Sure, now we’ve got GPS and radar. But how on Earth did the English find Jamestown over and over again? Use the stars to find your Latitude Use time to find your Longitude
• 25. Astrolabe Sextant Latitude from the Stars
• 26.
• At the North Pole where is the North Star?
• What is the latitude at the North Pole?
• 90˚
Latitude from the Stars North Star North Pole Equator Latitude = 90 ° Horizon
• 27.
• At the Equator where is the North Star?
• On the horizon @ 0˚
• What is the latitude at the Equator?
Latitude from the Stars North Star North Pole Equator Latitude = 0 ° Horizon
• 28.
• x = angle of the North Star above the horizon
• What is the relationship between x and latitude?
• x = Latitude
Latitude from the Stars North Star North Pole Equator Latitude = x ° Horizon x
• 29.
• x = angle of the North Star above the horizon
• Is there a relationship between x and latitude?
• x = Latitude
Latitude from the Stars North Star North Pole Equator Latitude = x ° Horizon x
• 30. World Time Zones Longitude from the Time
• 31.
• What time is it in Paris, Texas?
• ~8:30 am
• What time is it in Paris, France?
• ~3:30 pm
• How many hours in a day?
• 24 hours
• How many degrees of longitude on the earth?
• 360˚
Longitude from the Time
• 32. How many degrees of longitude constitute a time zone?
• 360˚/ 24 hours = 15˚ per hour
• So, roughly how many degrees of longitude separate Paris from Paris?
Longitude from the Time
• 33. putting it into practice Longitude from the Time
• 34. If 1 hour = 15 ° what does 1 minute equal? Longitude from the Time -divide each side by 60- 1 min (time) = 15 min (longitude) How’s that for confusing?