Location and Direction

Chapter 07

Latitude and Longitude

• The earth is gridded by imaginary lines called:– Longitude– Latitude

Building 16-105 @ Highline CC

• Latitude = 47.389806• Longitude = 122.299408

• http://itouchmap.com/latlong.html

GPS coordinates

• Global Positioning System

• Geocaching

Length of a degree of Longitude

• The length of a degree of longitude decreases as you travel from the equator to the north or south pole.

• Seattle: 1˚ ≈ 47 miles

Length of a degree of Latitude

• Parallels are constructed approximately the same distance apart.

• Seattle: Seattle: 1˚ ≈ 69 miles

Distances

• Your text book covers finding the distance between to locations.

• Remember: The earth can be approximated as a sphere.

Direction

• The angular relation of one line to another– Measured in Degrees– A complete circle is equal to 360˚

Degrees….not base10

• 360˚ = complete circle• 1˚ = 60’ = 60 minutes• 60’ = 60” = 60 seconds

• For example: 50˚30’45”

Calculations

• Converting from decimal degrees to degree/minutes/seconds.

• Adding Angles• Subtracting Angles– borrowing

Surveyor’s Compass

• Used to measure bearings or included angles.

True North (TN)

• Location of the North Pole

Magnetic North (MN)

• Magnetic North is where the compass north arrow points.

Magnetic Declination

• The meridian indicated by the needle on a compass seldom coincides with the true meridian.

• http://www.ngdc.noaa.gov/geomag/declination.shtml

Bearings• Angle to the north or south meridian from the

quadrant east or west.

Plotting a traverse

• POB – Point of beginning• Error of closure