Finding Your Way—Maps, Compass and GPS

Eagle Vision2005

Map and Compass - as navigation tools

Many people are of the mindset that with the introduction of GPS technology, the good ol’ Map & Compass are passé and no longer necessary…Believe that at your own risk!While GPS is a very powerful technology and while it can be used alone (without maps or compass), it has its limitations.Let’s have a look…

Limits of a GPS

Limits of a GPS

Limits of a GPS

Maps and Compass

How to use a compassBasics of contour mapsOrienting your map

The Basic Card Compass

Parts of a Card Compass

Azimuth and Bearing—two ways of giving directions

Azimuths uses 360 degrees---120 degrees

Bearings use 90 degrees and and cardinal directions– S 60 degrees E

Back azimuth or bears can be used to determine where you are from known points

DIRECTIONAL ARROW ON BASE PLATE

– Northwest

COMPASS HOUSING (AZIMUTH RING)

Chose your direction of travel—in this case 315 degrees

Turn the Compass housing to 315 degrees

How do you get from point A to point B?

NORTH END OF NEEDLE (RED)

RED ARROW (on compass housing) (SHED)

Put Red in the Shed.

Follow the direction of travel arrow

You are going 315 degrees

GN

MN

131

Choosing direction can be tricky

Declination---There is more than one north

Magnetic North, Grid North, and True North

Adjusting your compass to compensate

Contour MapsInformation on the mapContours as isolinesReading contour maps

Information on the Map

Contours as isolines

Reading Contour Maps

Orienting your map for field useLatitude and longitude or UTMThe magnetic field and compassMap orientation

Known locationResection and triangle of errorApproximations without a compass

Getting from point a to point b—route selection

Measuring DistanceMap measurementsOn-ground measurements

Approximations--Pacing Measurements

Slope problemsActual route traveled

GPSWhat is a Global Positioning System?

The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of satellites placed into orbit by the U.S. Department of Defense.

GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.

GPS

Elements of GPSControl Segment

Master Control Station Computes precise satellite orbits Prepares updated information Sends messages to each satellite

Monitor Stations Located throughout the world Track all GPS satellites Check operational health of the satellites Locate the exact position of each satellite Send information to the Master Station

Ground Antennas Monitor and track the satellites from horizon to horizon Transmit correction information to individual satellites.

Elements of GPSSpace Segment

The satellites and the Delta rockets that launch the satellites from Cape Canaveral, in FloridaA minimum of 24 functioning NAVSTAR satellites

Circular orbits at an altitude of 10,900 nautical miles. Orbits tilted to Earth’s equator by 55 degrees to ensure

polar coverage Powered by solar cells- satellites continuously orient

themselves toward sun Each of the satellites, positioned in 6 orbital planes,

circles the Earth twice a day

Elements of GPSUser Segment

The user segment includes the equipment of the military personnel and civilians who receive GPS signals

Surveyors Aircrafts and ships Delivery vans and emergency vehicles Agricultural sector In-car navigation Recreationalists (hikers, hunters, and cyclists) EAGLE VISION PARTICPANTS

How It WorksGPS units acquire their position on Earth by measuring their distance from three or more satellitesFor precise locations – including elevation measurements - the unit will need four satellitesThe GPS system measures the distance from the satellites to the receiver by timing how long it takes a radio signal to reach the receiver, then calculating the distance from the travel time

Velocity X Time = DistanceRadio signals travel at or near the speed of light

Pitfalls to AccuracyObstruction

Multi-path Issues

Atmospheric Delay

Human Error

Using Your GPSThe ControlsGetting from Point A to Point BWaypoints—before you leaveKeeping track of where you have beenWaypoints for data entry—data dictionaryPutting your GPS data on a digital mapMeasuring distance and elevation