Introduction Introduction

Summary of Topics - GPS - WAAS - Coordinate Systems - Datums

1973 – U.S. Air Force tasked with initial development1973 – U.S. Air Force tasked with initial development 1980’s – First civilian use1980’s – First civilian use 1995 – GPS declared “Fully Operational”1995 – GPS declared “Fully Operational” 2000 – “Selective Availability” suspended2000 – “Selective Availability” suspended Today – Wide variety of products and services utilize GPS technology, and the European Union builds its own GPSToday – Wide variety of products and services utilize GPS technology, and the European Union builds its own GPS A Brief History Of GPS

Apply GPS To Fire Situations Report a fire’s locationReport a fire’s location Navigate to a fire’s reported locationNavigate to a fire’s reported location Map a fire’s point of origin, or its perimeterMap a fire’s point of origin, or its perimeter Locate a safety zone, helispot, pump, water source, or other point of interestLocate a safety zone, helispot, pump, water source, or other point of interest Map roads or trails to be used for accessMap roads or trails to be used for access Map resources or improvements to be protectedMap resources or improvements to be protected Map dozer line to be rehabilitatedMap dozer line to be rehabilitated Document search, rescue, or recovery effortsDocument search, rescue, or recovery efforts

How does GPS work?

The Global Positioning System Control Segment Space Segment User Segment

Kwajalein Atoll US Space Command Control Segment Hawaii Ascension Is. Diego Garcia Cape Canaveral Ground Antenna Master Control Station Monitor Station

The Space Segment 24 or more satellites in Earth orbit that transmit: PRN codePRN code Ephemeris dataEphemeris data Atmospheric dataAtmospheric data Clock informationClock information An almanacAn almanac

JTrackJTrack Altitude 20,200 km 10,900 nm

Earth in a Cage of Satellites Current:Satellites Max:32 Satellites

 Military  Search and rescue  Disaster relief  Surveying  Marine, aeronautical and terrestrial navigation  Remote controlled vehicle and robot guidance  Satellite positioning and tracking  Shipping  Geographic Information Systems (GIS)  Recreation User Segment

How to Calculate a Position Measure the Distance to the Satellites

How to Calculate Distance Speed of Light x Travel Time Distance Time signal left satellite Time current

Minimum # of Satellites Required -Algebra Problem Unknown time latitude longitude elevation 4 4 Unknowns We Need 4 Satellites Equation satellite location

Minimum # of Satellites Required -Trilateration 1 satellite – somewhere on a sphere

Minimum # of Satellites Required -Trilateration 2 satellites – somewhere on a circle

Minimum # of Satellites Required -Trilateration 3 satellites – one of two points

Minimum # of Satellites Required -Trilateration Note: with 3 satellites, one point is on the earth’s surface and one is nowhere near. However, we still need the 4 th satellite because receiver clocks are inaccurate. 4 satellites – one point 3D GPS Location

When There are Only 3 Satellites 2D GPS Location Elevation - last known 2-5 X Error Rule

-Want tetrahedron as large as possible -Want index as low as possible Garmin Estimated Accuracy Relies on Dilution of Precision DOPs TDOP VDOP HDOP PDOP GDOP DOPs TDOP VDOP HDOP PDOP GDOP

Ideal Satellite Geometry N S W E

Good Satellite Geometry

Poor Satellite Geometry N S W E

Positions Recorded by Stationary GPS Receiver Garmin GPSmap76S 1 position/second 10 minutes WAAS Disabled 3.6 meters 3.1 meters

Errors (tens of meters) Ionosphere Troposphere Satellite Clock Errors Satellite Ephemeris Errors Multipath Receiver Noise

DGPS Site x+30, y+60 x+5, y-3 True coordinates = x+0, y+0 Correction = x-5, y+3 DGPS correction = x+(30-5) and y+(60+3) True coordinates = x+25, y+63 x-5, y+3 Real Time Differential GPS DGPS Receiver Receiver

WAAS satellites GPS Constellation WAAS Control Station (Position known) GPS receiver (Position with errors) Wide Area Augmentation System 25 Reference Stations (Position known)

WAAS Wide Area Augmentation System WAAS Satellite

Errors Reduced by WAAS Correction (multi-meter) Errors Reduced by WAAS Correction (multi-meter) Ionosphere Troposphere Satellite Clock Errors Satellite Ephemeris Errors Multipath Receiver Noise

Receiving WAAS Correction If WAAS signal intermittent- WAAS correction for SV 19 No WAAS correction for SV 11 WAAS correction for SV 19 No WAAS correction for SV 11

Caution! If WAAS Enabled – - 2D WAAS chosen over 3D uncorrected - WAAS chosen over DOP Recommendation If WAAS signal intermittent (example: under canopy) - disable WAAS

Signal Disruption Ionosphere Solid Structures Metal Electro-magnetic Fields

Good Data Collection Techniques External Antenna Map76S more accurate under canopy Sleeve Mounts Vehicle Brackets

Map Projections & Coordinate Systems

Projecting a Sphere Onto a Plane Three-dimensional sphere to two-dimensional flat map.

Examples of Several Projections Depending on the projection, a certain amount of distortion occurs when portraying the earth on paper.

Coordinate Systems (Projections) We Use – 2 Coordinate Systems Latitude / Longitude Universal Transverse Mercator (UTM) Garmin - 29 Location Formats

0º 0º Point of Origin Prime Meridian Equator (Longitude) (Latitude) 10º N 30º N 10º S Latitude & Longitude

Parallels of Latitude 10º 10º 10º 690 miles 10º S 0º N 10º N 20º N

Meridians of Longitude 10º 10º 110º W 120º W 690 miles 460 miles 240 mi 10º Equator To North Pole To South Pole

Three Ways To Express Latitude / Longitude on a Garmin

Three Ways To Express Latitude / Longitude (for the Same Location) hddd° mm’ ss.s” Degrees-Minutes-Seconds (Decimal Seconds) N 43° 40’ 55.8”, W 116° 17’ 14.1” hddd° mm.mmm’ Degrees-Minutes (Decimal Minutes) N 43° ’, W 116° ’ hddd.ddddd° Degrees (Decimal Degrees) N °, W °

Coordinate Systems hddd 0 mm’ ss.s”: N ’ 55.8” X W ’ 14.1” (55.8” / 60 =.93’) Different coordinates representing the same location: hddd 0 mm.mmm’: N ’ X W ’ (40.93’ / 60 = ) hddd.ddddd 0 : N X W UTM/UPS:11T m E m N

Example: Error in Latitude 35° 24´ 45˝ N 35° ’ N 1/3 of a mile

Lat / Long Shortcomings 1 minute ? ? 1 degree 1 1 degree ?

Universal Transverse Mercator measured in meters located in zones (1 - 60) include northing and easting are positive Coordinates Zone Easting Northing Latitude Band

UTM Zones in the Lower UTM Zones

160 UTM Grid Overlay 60 Zones, and 20 Latitude Bands 21 G M W X 80º S 84º N D C E F H J K L N P Q R S T U V Latitude Bands 21 T T Zones Equator

Garmin Uses – UTM bands Bands C - M, southern hemisphere Bands N - X, northern hemisphere UTM Latitude Band Latitude Band We Use – 2 GIS choices UTM Zone _ North UTM Zone _ South no “I” no “O” no “I” no “O”

If You Don’t Know Zone, Latitude Band… Entering Waypoints Zone – look up Band – enter any letter C – M for northern hemisphere, receiver will display correct one Collecting Waypoints Receiver figures it out!

UTM Location Format on a Garmin

What is a datum?

Datums WGS 84 NAD 83 NAD 27 Garmin - >100 Map Datums We Use – 3 Datums 1 meter meters

Example: Datum Shift in Arizona NAD83 N o, W o NAD meters

With a Garmin GPS Receiver you always collect in the right coordinate system and datum! Lat, Long WGS-84 UTC Lat, Long WGS-84 UTC Lat, Long NAD27 -8 GMT Lat, Long NAD27 -8 GMT UTM NAD83 UTC UTM NAD83 UTC Lat, Long WGS84 -9 GMT Lat, Long WGS84 -9 GMT Lat, Long NAD27 -8 GMT Lat, Long NAD27 -8 GMT UTM NAD83 GMT UTM NAD83 GMT Lat, Long WGS84 UTC Lat, Long WGS84 UTC Display doesn’t matter

Coordinate System? Datum? Coordinate System? Datum?

Review of Topics - GPS - WAAS - Coordinate Systems - Datums