basic gps course

8/3/2019 Basic GPS Course

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Basic GPS Course Or,

Where the heck am I ???


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NBGSARA Basic GPS Course 2

Agenda

09:00


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What is the Global

Positioning System? Space-based, worldwide radio-

navigation system. Constellation of 24

satellites(plus spares) ingeosynchronous orbits, and anetwork of ground controlstations.

Free access, highly accuratepositioning data is available to

GPS receivers anywhere in theworld. Developed and owned by the

US Dept of Defense.


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Many Different Receivers

Garmin, Magellan,Trimble etc.

Handheld, surveyor,permanent mountedin vehicles.
http://www.garmin.com/products/etrexLegend/http://www.garmin.com/products/gpsmap60cx/http://www.garmin.com/products/etrexsummit/http://www.garmin.com/products/etrex/


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How Does GPS work?

Satellitesconstantlytransmit a stream

of coded signalsat low power. GPS receivers are

programmed withthe generalpositions of thesatelliteconstellations,and their identifierdata.


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8/61NBGSARA Basic GPS Course 8

How Accurate is it? Depends on the type of receiver, and

terrain. Average handheld receiver:

10 to 15 meters newer models 5 meters

Graphic of person standing in a10 m circle



Before Proceeding!

Need to cover some basicbackground material.

Give you a better understanding ofwhat your GPS is telling you!



First things first! A Review!

Need to know about maps andcoordinate reference systems: Universal Transverse Mercator



Positioning/Mapping Review

When we discuss our position, we always usesome form of reference frame. We do thisautomatically:

Im about 10 feet in front of you ; or He lives next to the Tim Hortons ; or Im at Grid reference 318 765 .

The last statement uses a Grid reference anartificial grid of lines drawn on a map toprovide a standardized reference frame for allusers.



Universal Transverse

Mercator We use the UTM (Universal Trans Mercator)

grid reference system, since it is over-laid onall topo maps, and is widely accepted for

terrestrial operations. Maps are by necessity flat representations of

the curved surface of the earth. They useProjections to approximate the curves of theearths surface.

Mercator projections peel back the curvedsurface of the earth, and represent areas asflat Zones on maps.


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6366 60

15N

30N

45N

0N (Equator)

60N

75N

84N

15S

30S

45S

60S

75S

80S

Each UTM Zone is Centred on a Meridian

0m 500,000m 1,000,000m0m

2,000,000m

4,000,000m

6,000,000m

10,000,000m

8,000,000m

0m

2,000,000m

4,000,000m

6,000,000m

10,000,000m

8,000,000m The UTM coordinate

system is overlaid on top ofthe geographic (lat/long)coordinate system.

The two systems coincidein each of 60 UTM zonesat:

The equator Each zones central

meridian (63in eg) Boundary of each UTM

zone defined by meridians3east & west of centralmeridian (66& 60in eg)



UTM zones of Canada

New

Brunswickis in zone19 & 20 T



Horizontal linesmeasure Northing

Vertical linesmeasure Easting.

UTM positions areread Easting first,then Northing.



UTM for Our Area - 20 or 19T

TU

2019



So.if we look at the map..

We are 5,124,000 meters or5,124 km from the equator inZone 20This measurement is called thenorthing .


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A Grid Square (1 km x 1 km)

Read as: 60 (easting), 38 (northing)

What is the UTM for the X ?


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UTM Example

20T 3 83 000 51 24 000 (Buctouche Map)

20T 3 82 000 50 41 000 (Alma Map)

UTMZoneNo.

UTMLatitude

BandLetter

EastingValue

NorthingValue


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MGRS A subset of UTM

Divides UTM in smaller 100,000msquares identified by two letters eg.

LG An MGRS is made up of 5 parts:1) A zone,2) latitude band,3) MGRS square identification,4) an easting, and5) a northing


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MGRS example

20T LG 830 240 (Buctouche Map)

20T LR 820 410 (Alma Map)

UTMZoneNo.

UTMLatitude

BandLetter

EastingValue

NorthingValue

MGRSsquare

Versus 3 83 000 51 24 000

Versus 382000 5041000


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All those things to set ?

Why do we care about all these numbers? Because all GPS units are configured to work with

multiple reference frames, anywhere in the world.

They give far more information than is required forlocal navigation.

Practically, this means YOU must be able toconfigure a GPS to work correctly in YOUR zone(with your maps) and be able to extract the important

numbers from a position screen.


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Which of the 36 Grid

Systems????


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Datum

Once a grid system is chosen, that system mustitself be referenced to the land-masses shown onthe maps. This refers to the DATUM of thetopographical map you are using.

DATUM is the set of survey data used to createthe map. It is shown on the map, in a title block.

It is critical that your GPS be set to use the same DATUM as your map!


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Which of the 127 Datums to

Use????


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Check Datum Incorrect datum settings can result in

errors in position of hundreds of meters you may be using another country !

CHECKING and setting the position format, or grid,(UTM, MGRS) and the DATUM (usually NAD 83,

NAD 27, or WGS 84)is the first thing to do EVERY time you turnon a GPS.


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Now Back to the GPS


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What can a GPS do for you?

Provide your current position anywhere, anytime.

Display a line of past positions (atrack) and store them. Store a large number of known

locations waypoints. Give you real-time estimates on your

travel progress.


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Setup Position Format, Map

Datum Set-up position

format and map

datum to matchpaper map. If not using same

map datum can beout 100s of meters.


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Setup of Heading

True Magnetic

Grid

In our area thedifference between Trueand Magnetic is approx.18 - 19West

Which way is north?


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Setting Waypoints All have screens to set waypoints.


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Waypoint GOTO Once you have a waypoint,

you can navigate to it usingthe Goto command.

Newer models have a choiceof: Follow roads Follow off-road

Normally directs you in astraight line as -the-crow- flies.


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Navigating to Waypoint Navigating to a

waypoint: Gives compass

bearing, Distance to point, Estimated time to get

there, based oncurrent rate of travel.

Heading: Your moving direction.

Bearing: The direction from your current

location to a destination.


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Be Careful with GOTO

GPS tells you to go 3.8kmat a bearing of 248true.

Have to look at the map to

see what terrain isbetween the start andend position.

Need to plan your route!


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Setup of Tracks

Turn Track LogOn

Set colour tosomething otherthan transparent .


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A Point About Accuracy

Training exercise, Irishtown Nature Park:28 Aug 2004, 9 to 11pm


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Position Formats

Position:Map Datum:North Ref:

Position: Decimal degrees(hddd.ddddd )

Map Datum: WGS84North Ref: True

Position: Degrees, decimal minutes( hddd mm.mmm )

Map Datum: WGS84North Ref: True

Position: MGRSMap Datum: NAD27/WGS84North Ref: Grid
http://images.google.ca/imgres?imgurl=http://www.city.red-deer.ab.ca/NR/rdonlyres/5707A3B7-139C-4F42-A5E7-5CA9ABB1CED9/0/HelicopterinSky.jpg&imgrefurl=http://www.city.red-deer.ab.ca/Connecting%2Bwith%2BYour%2BCity/City%2BServices%2Band%2BDepartments/RCMP/General%2BRCMP%2BInformation/RCMP%2BPhoto%2BGallery.htm&h=150&w=200&sz=8&hl=en&start=2&tbnid=Xj4i_RlW4-OFdM:&tbnh=78&tbnw=104&prev=/images%3Fq%3Drcmp%2Bhelicopter%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG


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SAR Uses

Finding start positions Marking end positions

Mapping trails found Route planning getting around unsafeareas

Navigate to another team, waypoint, etc.with a GOTO

What happens if the GPS fails how do Iget back home?


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Downloading/Uploading

Can download/upload: Waypoints

Tracks Routes to/from GPS units into

mapping software
http://www.garmin.com/products/gpsmap60cx/


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Always Remember! 1. Allow unit to lock on to 4 or more satellites.2. ALWAYS save your starting point as a waypoint (lets call

it home ) write it in your field notebook.3. Clear the track log & old waypoints before starting a task.4. Set the odometer/trip to zero.5. Keep extra batteries and keep GPS warm.6. Does NOT replace map & compass. Take map & compass

with you.7. Always check/set (according to map reference):

Position format Map datum North reference


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The only way to ..

be comfortable with your GPS is to practice, (on your sofa)

.. practice , (out for a walk)

.. practice (in your car) !


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So, Dont forget!

Which Map Datum ?

Which Position Format or Grid?

Which North Reference?Magnetic

Grid True


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GPS Specific Screens

Lets run through the screens forGPSmap60Cx or 76Cx


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GPSmap 60Cx / 76Cx

Satellite Main Menu Map Trip Compass


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Trip Push Menu Choice of 7 itemsto reset .

Suggest choosingthese fields for SARpurposes

P h M


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Compass

Note:

Heading Field

Bearing Field

Best to use:

Bearing Pointerfor SAR

ALWAYS ..

STOP Navigationwhen finished witha GOTO.

Push MenuWhen a GOTO is Active.


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Creating a Waypoint

Push Mark

Push Enter ,inside name fieldto get on-screen

keypad

Push Enter ,inside Location

to get on-screenkeypad


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Finding a Waypoint

Push Find List Push MenuGoto

Waypoint

ALWAYS ..STOP Navigationwhen finished witha GOTO.


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Hands-On!

Now lets put some waypoints intoour GPS and see what we can find!


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Outdoor Exercises


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R eference

M aterial


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Electronic Maps

Mapquest find latitude/longitude http://www.mapquest.com/maps/main.adp?for

mtype=latlong&cat=&address=&city=&state=&

zipcode= Google Earth: http://earth.google.com/ Map Source: (from Garmin)

Topographic maps Metro Guide maps

Service NB NB Atlas: http://www.snb.ca/gdam-igec/e/2900e_1.asp


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Reference Material

Two good manuals: http://www.garmin.com/aboutGPS/manual.html

GPSGuideforBeginners_Manual.pdf

UsingaGarminGPSwithPaperLandMaps_Manual.pdf US Coast Guard service interruptions

http://www.navcen.uscg.gov/gps/gpsnotices/default.htm

Geocache web site: http://www.geocaching.com/

Topographic map information: http://maps.nrcan.gc.ca/topo101/index_e.php http://atlas.nrcan.gc.ca/site/english/maps/topo/map

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