Introduction to the Global Positioning System by Dr. Stephen C. Brown University of Alaska at Fairbanks Mat Su /Copper River District

WHAT IS GPS? Satellite based radio positioning system Developed and maintained by the U.S. Department of Defense Made up of three segments: W Space W Control W User or Ground receivers Used for obtaining accurate locations any where on earth

GPS Is An Excellent Mapping Tool –Instantly gives: Altitude Speed Longitude and Latitude

Space Segment

USER SEGMENT LAND SEA AIR NEED Four SV’s.

Maintained by the Department of Defense Control Segment

How It Works…. Trilateration

Increasing Accuracy: Wide Area Augmentation Service (WAAS) 100 m15 m <3m

Recognizing Coordinate Systems Format Type Example Coordinate (all are same position) Degrees, Minutes, Seconds (DMS): ’ 15” Decimal Minutes (DM): ’ Decimal Degrees (DD): ’ 15” is the same as ’ is the same as

Universal Transverse Mercator (UTM) Coordinates A “metric” coordinate system 5V E N meters Easting meters Northing

UTM Zones

The Right Datum is Important! GPS data stored in WGS84/NAD83 datum and displaying them with GIS data in NAD27 datum can result in 100's of meters in error!

Error Problems in Alaska SV’s are on an southern equatorial plane Mountains often block the sky Extreme cold impact batteries

PRACTICAL APPLICATIONS Navigation Sailing, hiking and aviation Collecting and locating way-points Locating Features Stocking locations or stream surveys Endangered or sensitive species locations Locating trails or physical structures GIS Collecting GPS data along with attribute data Mapping and database update Surveying Locating Control Points quickly

Garmin GPS Receivers Inexpensive and downloadable Available locally for less than $150 Most GPS receivers similar in operation

SV Visibility clear viewobstructed view

SkyView Page Satellite status appears while the unit “finds” the satellites Acquisition can take several minutes

Waypoints track waypoint

Creating Waypoints

Selecting Waypoints

What is Geocaching? Geocaching is a worldwide “scavenger hunt” using GPS to find “caches” of treasure. The only rules are to leave something if you take something and do not disturb the cache

GPS Online Resources

Steve Brown: Mat-Su/Copper River District University of Alaska Fairbanks Cooperative Extension Service