Welcome Students!

Where is Here?N

E

S

W

Earth’s Grid

Equator: line that divides the Earth into Northern and Southern hemispheres.

Prime Meridian: line that divides the Earth into Eastern and Western hemispheres.

Latitude ~ Fatitude

Latitude Lines run East West

Latitude: measures North or South of the Equator

Longitude lines run North South

Longitude: measures East or West of the Prime Meridian.

What is GPS?

Hand held device used to communicate

with the satellites.

The location is given in

longitude and latitude

coordinates.

You Are

Here

Communication

The GPS handheld receiver uses radio waves to talk to the satellite and find its location.

Trilateration: using a set of 3 points or more

to find the location of an unknown point.

Satellite 1

Satellite 3

Satellite 2

Longmont

Ft. Collins

DenverBoulder

State 3 =

Satellite 1 16 cm

Satellite 2 13 cm

Satellite 3 13.4 cm

Satellite 4 10.5 cm

State 1 =

Satellite 1 13 cm

Satellite 2 11 cm

Satellite 3 15 cm

Satellite 4 13.7 cm

State 2 =

Satellite 1 11 cm

Satellite 2 17.2 cm

Satellite 3 9 cm

Satellite 4 16 cm

?

?

ColoradoMinnesota Missouri

How far???

GPS receivers use time to know how far away the satellites are.

Example: Lightening and Thunder in a storm.

How Far?• GPS satellites measure distance using the speed of light

• Light travels at 186,000 miles per second

• If it takes a signal 10 Seconds to travel from a GPS receiver to a GPS satellite, how far apart are they?

• 10 seconds x 186,000 miles per second = 1,860,000 miles

• The sun is 93,000,000 miles away…how long do you think it takes the light from the sun to reach Earth???

• 93,000,000 ÷ 186,000 = 8 minutes!

Bringing it all together

GPS can be used to tell us where we are on Earth

Why is GPS so important???

GPS uses time to find distance

Latitude and Longitude let us know exactly where we are.

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