YSSR GPS LECTURE

1
(No Transcript)
2
SII M2 Navigation TheoryGPS
March, 2007
3
YSSR GPS Course - Outline

• Start 0900 Classroom session
• Introduction to GPS
• Brief history of development
• System components
• How does it work?
• What can it do for us
• What can it NOT do for us
• Coffee Break

4
YSSR GPS Course - Outline

• Positioning/Mapping review
• Mapping systems/projections
• MGRS positioning example and exercises
• Common mapping/GPS terminology
• Typical GPS receiver specifications and features
• Screen examples from selected GPS units
• GPS Mapping Demo (OziExplorer)

5
YSSR GPS Course - Outline

• GPS Set-up exercise
• Datum, units, format, etc.
• Waypoint entering/retrieval exercise
• General questions and answers
• Lunch Break 1200 to 1245
• Map Exercise 1300-1400
• Brief Outside Exercise
• Write GSAR exam 1500 hrs

6
GPS - Introduction

• What is the Global Positioning System?
• Space-based, worldwide radio-navigation system
• Uses a constellation of 24 satellites (plus
  spares) in geosynchronous orbits, and a network
  of ground control stations.
• Free access, highly accurate positioning data is
  available to GPS receivers anywhere in the world.

7
GPS Constellation
8
GPS Brief History

• Developed (and owned) by the US DOD
• In development since the early 1970s
• First satellite launched in 1978, full
  constellation by 1994
• Originally intended to be a military tool
• 2 levels of service
• Standard Positioning Service (SPS)
• Precise Positioning Service (PPS)
• Public uses SPS. Selective Availability (SA)
  limited accuracy of SPS
• SA removed by Clinton in May 2000

9
GPS 3 Segments
10
GPS Segment Components

• Space segment (Satellite Vehicle SV)
• 2 tonne weight, 12m solar panel wingspan
• 4 Atomic clocks
• 10 year design life
• Several generations of satellites now in orbit
• Assembled by several US Defense Contractors,
  first ones by Lockheed Martin Corp.

11
GPS Space Segment SV
12
GPS Ground Segment Control

• Master control station is at Schreiver AFB in
  Colorado.
• Defense contractors maintain a duplicate ground
  control station, which is activated semi-annually
  to ensure readiness.
• Monitor satellite health, positional accuracy,
  transmit correction and information updates to
  satellites.
• 4 unattended monitoring stations also relay data
  to master control station and SVs.

13
GPS Ground Segment Control
Colorado Springs (Falcon AFB)
Master Control Station
Monitor Station
Ground Antenna
14
GPS User Segment US!

• Any one of dozens of forms of passive GPS signal
  receivers configured to receive either SPS or PPS
  frequencies.
• Receivers can be as small as a watch, but are
  more commonly a hand-held, 12-channel receiver
  with a built-in antenna.
• SPS is free and available to anyone, 24/7.

15
Handheld GPS Receivers

• Garmin Venture Cx
• 229 ( Memory Card)
• Garmin Rino 530
• 500
• Garmin 76csx
• 459
• Survey Grade Units
• gt5,000

16
How Does GPS Work? 1

• Uses satellite ranging.
• Satellites travel in predictable paths (i.e. we
  can predict where they are in relation to any
  point on the earth at any time)
• Radio frequency signals travel at a predictable
  (and constant) speed the speed of light.
• GPS receivers are programmed with the general
  positions of the satellite constellations, and
  their identifier data.

17
How Does GPS Work? 2

• SVs constantly transmit a stream of coded
  signals at low power.
• Signals include timing data that receivers can
  compare to predicted timing data programmed in
  their memory.
• By determining the time difference in the
  predicted vs. the actual signals, and multiplying
  by the speed of light, a distance to a satellite
  can be determined.

18
How Does GPS Work? 3

• When the distances to at least 3 satellites are
  known, a 2-dimensional position can be
  determined. Altitude is unknown in a 2-d
  position.
• When 4 or more SVs are resolved, 3-d positions
  are possible (allows more accurate elevation
  determination)
• More SVs are better for improving position
  accuracy.

19
How Does GPS Work? 4
20
How Accurate Is It?

• SPS accuracy advertised to be /- 15m, 95 of the
  time.
• Many schemes to improve GPS accuracy
• Differential GPS
• Requires separate receiver
• WAAS (North America)
• Not very effective inland NB with tree cover
• EGNOS (European WAAS)

21
Errors yes, there are some

• Sources of Errors
• Satellite errors (clock, orbit and control)
• Accidental/Intentional signal jamming
• Ionospheric/atmospheric interference
• Multipath signals
• Poor satellite geometry (DOP)
• Shading/poor overhead visibility
• Receiver clock errors
• Carbon interface errors MOST COMMON.

22
What Can GPS Do for You?

• Can provide you with your current position,
  anywhere and at any time, with a reasonable
  degree of accuracy.
• Can display a line of past positions (a track)
  and store them.
• Can store a large number of known locations
  (waypoints) and provide a range and bearing to
  any one of them.
• Can give real-time estimates on your progress to
  or from a known location (range, bearing, ETA,
  etc.)
• Can provide an estimated altitude, and can keep
  accurate time.

23
Something to note..
24
What Will GPS NOT Do for You?

• Will NOT give you much useful data without a
  suitable MAP.
• GPS will NOT replace map and compass skills
• Will NOT necessarily give an accurate indication
  of magnetic north, or current heading.
• Will NOT assist you home unless you can tell it
  where home is in a way it can understand.
• Will NOT be accurate over short distances (less
  than 15m)
• Will NOT be any use without sufficient battery
  power (consider cold temps) or a clear enough
  view of the sky.
• Will NOT replace common sense.

25
GPS Requires Extra Vigilance!

• IN SEARCH AND RESCUE WORK, AND IN MOST OUTDOOR
  ACTIVITIES, GPS WILL NOT REPLACE MAP AND COMPASS
  WORK, AND CAN REQUIRE MORE VIGILANCE IN
  NAVIGATION THAN LESS.
• GPS is only one more tool, and it must be used
  carefully, along with all other tools available
  for navigation.

26

• Do we need a 15 min break ?

27
Positioning/Mapping Review 1

• When we discuss our position, we always use
  some form of reference frame. We do this
  automatically
• Im about 10 feet in front of you or
• He lives next to the Tim Hortons or
• Im at Grid reference 19 FL 81935 902937
• The last statement uses a Grid reference an
  artificial grid of lines drawn on a map to
  provide a standardized reference frame for all
  users.

28
Positioning/Mapping Review 2

• There are many reference frames used around the
  world, some will be familiar with Latitude and
  Longitude, but that is only one of dozens.
• Hiking - UTM (Universal Trans Mercator) grid
  reference system, since it is over-laid on all
  topo maps, and is widely accepted for terrestrial
  operations. Easy and efficient to use in the
  field.
• MGRS (Military Grid Reference System) is a
  version of the UTM grid that is even easier to
  use. Now adopted by YSSR/TCGSAR
• YSSR members will be able to set GPS unit to read
  Latitude Longitude as required for Aircraft and
  marine operators.
• Maps are by necessity flat representations of the
  curved surface of the earth. They use
  Projections to approximate the curves of the
  earths surface.
• Mercator projections peel back the curved
  surface of the earth, and represent areas as flat
  Zones on maps.

29
YSSR Mapping Review

• Transition From Forest Inventory (Traditionally
  Lat Long)
• To Forest Inventory- Custom (via UTM /MGRS Grid
  overlay)
• Also use Digital Maps
• - SNB Orthophoto series (NAD 83, stereographic
  double projection, 110,000 scale)
• Garmin Topo Canada (user can set preferences)
• eTopo Series Canada
• Other digital maps as they become available

30
UTM / MGRS Grid Zones Of The World
31
UTM / MGRS Grid Zones Of The World
32
UTM / MGRS Grid Zones Of The World
100,00 m 100 km
14UML
100,00 m(100 km)
33
Positioning/Mapping Review 4 LL

• UTM zones of Canada

34
Positioning/Mapping Review 5

• One UTM zone segment, showing the central
  meridian and shape of the segment.
• New Brunswick is half 19 and half 20

35
Positioning/Mapping Review 3
36
Positioning/Mapping Review 6

• Horizontal lines measure northing
• Vertical lines measure Easting.
• UTM positions are read Easting first, then
  Northing.

37
Positioning/Mapping Review 7

• The Northing numbers mean actual distance North
  of the equator.
• Since Canadas Southernmost point is over
  4,620,000 m north of the equator, all Northing
  figures will be above this number.
• The Easting numbers measure from an imaginary
  line 500,000 m to the west of the zones central
  meridian.
• This means that lines to the left of the central
  meridian will be lower than 500,000, and those to
  the right higher.

38
Positioning/Mapping Review 8

• 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
  for local navigation.
• Practically, this means YOU must be able to
  configure a GPS to work correctly in YOUR zone
  (with your maps) and be able to extract the
  important numbers from a position screen.

39
Positioning/Mapping Review 10

• Once a grid system is chosen, That system must
  itself be referenced to the land-masses shown on
  the maps. This refers to the DATUM of the
  topographical map you are using.
• DATUM is the set of survey data used to create
  the 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!

40
Positioning/Mapping Review 11
41
Positioning/Mapping Review 11
42
Positioning/Mapping Review 12

• Incorrect datum settings can result in errors in
  position of hundreds of meters.
• CHECKING and setting the position format (UTM)
  and the DATUM (usually NAD 83, or NAD 27) is the
  first thing to do EVERY time you turn on a GPS.

43
Positioning/Mapping Review 13

• Typical position read-out from a GPS.
• Note the UTM.
• Note the UTM Zone designator, 19-T.
• Note the 14 digit position read-out!

44
Positioning/Mapping Review 14

• These are the numbers we are interested in.
• Our position would be read as 0683676
• 5098786

83 67
plot to paper map
98 78
45
Positioning/Mapping Review 13

• Typical position read-out from a GPS.
• Note the MGRS.
• Note the UTM/MGRS Zone designator, 19-T.
• Note FL Grid ID
• Note the 10 digit position read-out!

46
Positioning/Mapping Review 14

• These are the numbers we are interested in.
• Our position would be read as 65207
• 89453

65207
plot to paper or digital map
89453
47
Positioning/Mapping Review 14
GSAR Format !
48
GPS Navigation Terms 1

• UTM
• Universal Transverse Mercator (grid), or our
  common reference frame.
• Datum
• The set of survey or mapping data that were used
  to create a topographical map.
• SVs
• Space Vehicles, or GPS satellites.

49
GPS Navigation Terms 2

• Position (POS, POSN)
• Your current location, given in reference to a
  chosen grid system.
• Waypoint/Landmark (WPT, LMK)
• A location described by a name and a grid
  reference.
• Bearing (BRG)
• The angle, in degrees, from magnetic North
  between your current position and a waypoint.

50
GPS Navigation Terms 3

• Range (RNG)
• The straight-line distance between your current
  position and a waypoint.
• Track (TRK)
• A group of past positions, strung together in
  sequence, showing a relative path.

51
GPS Navigation Terms 4

• Heading (HDG)
• Your current direction of travel
• EPE
• Estimated Position Error
• XTE or CTE
• Cross-Track Error
• ETA, TTG
• Estimated Time of Arrival, Time To Go

52
Typical Hand-Held GPS Receivers

• 12 - Channel parallel receivers now universal
• Water resistant, if not submersible.
• Rugged cases with built-in antenna.
• 12-30 hrs operation on batteries.
• Capable of external power and data transfer.
• Most have basic mapping capabilities.
• Various added features
• Digital compass, altimeter, databases, etc.

53
General Usage Tips

• ALWAYS check setup and clear track log.
• Be patient - allow unit to lock on to 4 or more
  satellites before using data.
• ALWAYS save your starting point (Command Center,
  trail head, parked car, etc.). Pick a unique
  starting point that can be found visually from 40
  - 50m away.
• Clear the track log before starting on a task.
• Keep batteries fresh and keep GPS warm.
• Update firmware/software when possible.

54
Hand-Held GPS Units
All have basic satellite reception screens

• Number and ID of SVs received
• Indication of signal quality
• Estimated position accuracy

55
Hand-Held GPS Units
All have basic satellite reception screens
Garmin Legend
Garmin etrex
Garmin GPS 76S
56
Garmin 76

• 5 Main pages

57
Hand-Held GPS Units

• All have system and navigation set-up screens

Garmin 76
Garmin 76C
58
Hand-Held GPS Units

• All have basic position/navigation screens

Garmin GPS 76S
Garmin etrex
59
Hand-Held GPS Units
All have some form of accessing the waypoint
storage

• Waypoints are stored with a symbol and a name.
• Once a waypoint is selected, it may be used to
  create a go to screen.

Garmin 76
Garmin etrex
60
Hand-Held GPS Units

• Pressing enter will set up a go to screen,
  automatically giving a range and a bearing to the
  chosen waypoint.
• Waypoint features may also be edited in this
  screen.

Garmin etrex
61
Hand-Held GPS Units
Many have compass pages

• Note that the compass is not really a compass.
  It tells you your current heading. This is only
  accurate when you are moving.

Garmin etrex
Garmin 76
62
Hand-Held GPS Units

• Unless you have a built-in Digital Compass, and
  it is calibrated, and turned on.
• Note that most must be held level as well.

Garmin GPS 76S
Garmin
63
Hand-Held GPS Units
All units have some form of tracking/plotting
page.

• Some have a base map showing basic features.
• Some units allow topographical information to be
  displayed.

64
GPS Map screens
Garmin GPS 60CS
Garmin 76
Garmin Legend
65
Map screens
Garmin 76csx
Garmin 76
66
Map screens Killarney Lake
Garmin 76csx
Garmin 76
67
Killarney Lake - Waypoints
76 Csx with waypoints
76 map with waypoints
68
GPS Mapping

• YSSR is now using downloaded tracks from teams
  returning from taskings.
• Confirms ACTUAL path and assists in continued
  Search Management process
• Updated PODs, elimination of areas, identifies
  new tracks/trails not on maps, etc.
• Many recreational software mapping packages
  available.
• OziExplorer, Fugawi, Touratech QuoVadis, etc.

69
GPS Mapping

• Magenta line is recorded track

70
GPS Mapping

• Close-up of track resolution

71
GPS Mapping

• Switch to OziExplorer for Demo - GM

72
GPS Hands-On Exercise

• Turn on GPS units.
• Check Datum
• Check position format
• Check units
• Clear tracks, and clear unwanted waypoints.
• Reset trip odometer

73
GPS Hands-On Exercise

• Settings should look similar to these

Garmin 76
Garmin etrex
74
Hand-Held GPS Units

• All have basic position/navigation screens

Garmin GPS 76S
Garmin etrex
75
GPS Hands-On Exercise

• Program the following waypoints into your GPS
• 82026 92945 (name it waypoint loc 1)
• 81851 92945 (name it waypoint
  -loc2)81725 92914 (name it waypoint -
  loc3)
• 81867 92846 (name it waypoint loc4)
• - Map Datum - WGS 84- Position Format - MGRS

76
Positioning/Mapping Review
Killarney Lake Map Exercise (Azimuths/Distance)
77
GPS Hands-On Exercise

• ALWAYS check setup and clear track log.
• Be patient- allow unit to lock on to 4 or more
  satellites before using data.
• ALWAYS save your starting point (Command Center,
  trail head, parked car, etc.). Pick a unique
  starting point that can be found visually from 40
  - 50m away.
• Clear the track log before starting on a task.
• Keep batteries fresh and keep GPS warm.
• Update software when possible.

78
Now, out of the classroom