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Term: GPSWebsite: http://geography.about.com/od/

geographictechnology/a/gps.htm

Read the article about GPSWhat are the 8 things you need to know?

GPSGlobal Positioning System

1. The Global Positioning System is composed of twenty-four satellites 12,500 miles above the earth. The satellites are spaced in orbit so that at any time a minimum of six satellites will be in view to users anywhere in the world.

2. Using a portable or handheld receiver unit that receives data from the closest satellites, the GPS unit triangulates the data to determine the unit's exact location (typically in latitude and longitude), elevation, speed, and time. This information is available around-the-clock anywhere in the world and is not dependent on weather.

3. The GPS unit you can buy over the counter at many retailers is as accurate as those used by the military today.

4. Many handheld Global Positioning System units contain base maps of a region of the earth but most can be hooked up to a computer to download additional data for specific locales.

GPS

5. GPS was developed in the 1970s by the U.S. Department of Defense so that military units can always know their exact location and the location of other units.

6. Global Positioning System is free to the world, developed and paid for by U.S. taxpayers through the U.S. Department of Defense.

7. The U.S. military maintains the capability to prevent enemy use of GPS.

8. Global Positioning System in included as part of in-vehicle navigation systems and cellular phones.

Definition

• The Global Positioning System (GPS) is a group of satellites in earth orbit that transmit precise signals, allowing GPS receivers to calculate and display accurate location, speed, and time information to the user.

• GPS Receiver – receives the signals and translates them into useable information

Longitude & Latitude

• N ##° ##’ ##” Degrees, Minutes, Seconds

• 1° = 70 miles

• 1’ = 1.2 miles

• 1” = .02 miles (108 ft)

• May see in decimals

• N ##° ##.####

UTMUniversal Trans Mercator

•Series of grids going down to

•1000 X 1000 meter grids

Topographic Maps

• Name: ____ Quadrangle• Series: 7.5 Minute

• Corners give:– Longitude & Latitude– UTM grids

Topographic Maps

• May or may not have gridlines

• If there are grids: UTMs– 02 55 235– 42 89 852

• Longitude & Latitude – lines are not filled in– N 38°45’ 230”– W77°27’ 310”

Datum

• There are many different UTM systems

• Check the setting of the receiver to make sure you are on the right one.

• The WGS 84 is currently the one in use for GPS system and is valid until 2010.

GPS Receiver

• Can give location– UTM– Longitude & Latitude

• Can give direction when moving– More expensive models have built in compass

• Can mark waypoints– Mark a track you plan to take

• Can track routes– Can find the way you came

GPS Instructions

• Garmin ETrex H

• Simplest off road model available

• Cannot load maps onto this model

• Can exchange data with the computer

• Video

Data exchange

• Can upload/download data from internet

• Google Earth

• ArcSoft

Today

• 4 Teams – – Turn on GPS– Track 4 satellites– Accuracy 15’ or less