Air Operations Branch Director Course

2. U.S. AIR FORCE AUXILIARY Air OperationsBranch Director Course Navigation Fundamentals & Understanding GPS for Sortie Planning

3. Goals for understanding • Prepare mission staff to be able to plan and brief missions that can be executed efficiently and conveniently with our equipment • Navigation fundamentals • Capabilities and limitations of GPS • Capabilities of Apollo GX55 GPS units in Minnesota Wing aircraft • What information is needed to program the GPS unit for search patterns • What can and cannot be programmed in the GX55 • What can be “improvised” • Learn about the “gotchas” using GPS

4. PART 1Navigation fundamentals • Latitude and longitude • Describing directions

5. Latitude • Parallels • Measure How Far North or South of Equator • Zero Degrees is Equator • “90 Degrees North” is the North Pole • “90 Degrees South” is the South Pole North Latitudes Equator South Latitudes

6. WestLongitude Prime Meridian East Longitude Longitude Longitude • Half Great Circles Intersecting at the Poles • Measure How Far East or West of England • Zero Degrees is Prime Meridian (England) • Numbers between 0 and 180 are either East or West Longitude • 180 Degrees is opposite side of globe from England • near international date line in Pacific Ocean

7. Latitude and Longitude • Latitude is Based on Earth’s motion • Axis of rotation defines poles and Equator • Longitude is Arbitrary • Greenwich, England was chosen for ‘prime meridian’.

8. Twin Cities Northern Minneapolis is at 45 Degrees North (half way between the Equator and North Pole!) 93 Degrees West is roughly the Eastern edge of St. Paul. The Northwest corner of the state: Exactly 49 Degrees North Roughly 97 Degrees West Where’s Minnesota?

9. How Big is One Degree? • Degrees of Latitude are always the same distance apart, about 60 Nautical Miles • Degrees of longitude vary in distance – near the poles the lengths are quite small. • In Minnesota, a degree of longitude is about 40 to 44 Nautical Miles across

10. Dividing Degrees into Smaller Units • A ‘Minute’: 1/60th of a Degree • roughly a mile in size • Minutes are usually broken down into tenths of minutes • Alternatively, a ‘Second’ is 1/60th of a minute

11. Expressing Latitude and Longitude in Degrees and Minutes • Small high circle after number denotes degrees • Apostrophe after number denotes minutes • Example: Minneapolis Flying Cloud Airport 44o 49.63’ N 93o 27.43’ Wread as…44 degrees 49.63 minutes North 93 degrees 27.43 minutes West

12. Expressing Latitude and Longitude in Degrees, Minutes, and Seconds • A double-quote after a number denotes seconds • Example: Minneapolis Flying Cloud Airport 44o49’ 37.8” N 93o27’ 25.8” Wread as…44 degrees 49 minutes 37.8 seconds North 93 degrees 27 minutes 25.8 seconds West

13. Determining Coordinates from a Chart

14. Expressing Direction: The Compass Rose 360 330 30 N 300 60 W E 270 90 240 120 Directions are expressed as a number from 001 to 360 S 210 150 180

15. Magnetic Variation • The Magnetic North Pole is located in Canada, not at the True North Pole. • The difference in direction between the two poles is measured and referred to as magnetic variation

16. Magnetic Variation in the US -15º +20º +15º -5º -10º 0º +10º +5º Easterly Variation Westerly Variation Note: These lines move over the years because the magnetic north pole is in motion Agonic Line

17. PART 2 - GPS • Overview of GPS for SAR • Motivation • Potential uses for SAR • How it works • Accuracy • Limitations and Gotchas • Terminology • Describing search patterns for the GX-55 • Improvising

18. Motivation • GPS is a powerful tool for search and rescue • Allows very precise search patterns • Makes manageable what would otherwise be very difficult patterns • Expanding square at any angle • Creeping line along a course • Offset route searches • Grid searches over indistinct terrain • GPS should be our primary tool for Search and Rescue navigation • GPS is of course also very handy for general navigation

19. Potential uses of GPS for Air and Ground SAR • Getting to/from a search area • Going to a location designated on a map • Going to a site identified by another SRU • A ground team going to a site previously identified by an aircraft • Navigation while conducting a search pattern • Clue logging (and re-finding)

20. GPS for SAR: Potential advantages • More flexible search area partitioning • More accurate logging • More accurate search lines • Easier and more accurate communication of location information

21. Other GPS SAR Uses • Electronic distress signals • PLBs – Personal locator beacons • ELTs – Emergency locator transmitters • EPIRBs – Emergency Position Indicating Radio Beacons • New 406 MHz digital beacons sometimes transmit GPS coordinates • GPS then becomes a tool for both the rescuer and the rescued

22. How it Works – The Basics • Spaced-based system (unlike Loran or VOR) • ‘Constellation’ of 24 satellites in six orbital planes • 21 active satellites plus 3 operating spares • In “High” orbit of about 12,000 miles • Each circles the Earth about every 12 hours

23. How it Works – The Basics • GPS satellites transmit information • “Pseudo-random” code with time information • Satellite orbital position data • “Almanac” data • “Ephemeris” data • Updated atmospheric models • GPS receiver uses this data to figure out what time it is and what time the signals were sent

24. How it Works – The Basics • GPS receiver measures distance to satellites by determining the amount of time that the radio signal takes to travel from each satellite • Each distance measurement effectively defines a sphere around a satellite • Multiple satellites must be used to determine a position • Given two satellites, two sphere intersect to determine a circle • Given three satellites, a sphere and a circle intersect to determine two points • A fourth satellite can determine a positive 3D position

25. Accuracy • A complex question • DOD has a 66 page document describing the performance of GPS Standard Positioning Service (SPS) • The short story • Garmin states that their GPS receivers “are accurate to within 15 meters on average” • Typically about 6 to 12 Meters accuracy can be seen

26. Accuracy • Accuracy and reliability is actually a complex subject. There are many factors that can impact system. • Receiver errors • Atmospheric (ionosphere) errors • Solar activity (sun spots and solar storms) • Location of receiver (some parts of the Globe get better coverage than others) • Orbital errors (inaccuracies in the reported orbital position) • Poor satellite geometry (satellites lined up or bunched up) • Limited number of satellites in view • Satellite malfunctions (or satellites taken out of service) • “Multi-path” errors (radio signal reflections) • Results vary hour by hour, day by day

27. Accuracy • There is a substantial difference between typical accuracy and worst-case accuracy • Described as a statistic: x% had an error of y meters or less Typical 95% horizontal error results for a typical day: Errors worse than 30 meters are possible given the potential for various atmospheric conditions and receiver faults and the possibility that satellites can be taken out of service

28. Accuracy and“Selective Availability” • Past feature of GPS SPS that purposefully degraded accuracy of position determination for non US-military use • Civilian accuracy was typically about 100 meters under Selective Availability • SA was discontinued May 1, 2000 • Has not been used since • It's been replaced by “selective deniability,” which allows the US military to geographically designate areas in which to degrade GPS quality.

29. Comparing Accuracy with and without SA – A sample The plots show that SA causes 95% of the points to fall within a radius of 60.7 yards. Without SA, 95% of the points fall within a radius of 7.9 yards.

30. Comparing Accuracy with and without SA – Recap • Before, with 100 meter typical accuracy allowed you to identify what stadium you were in • Now with 6-12 meter typical accuracy, you can tell about which yard line you are on

31. Accuracy – WAAS • Wide-Area Augmentation System • Designed specifically for aviation • Commissioned by FAA in 2003 • Uses ground stations and satellites • 25 ground reference stations cover the entire US and parts of Canada and Mexico • Augments GPS Standard Positioning Service • Provides better integrity and accuracy • Typical accuracy of 3-5 meters horizontal, 3-7 meters vertical • Can be used for precision approaches

32. Accuracy – WAAS • How it works: • Two master stations, located on either coast, collect data from the 25 reference stations and create a GPS correction message. • This correction accounts for GPS satellite orbit and clock drift plus signal delays caused by the atmosphere and ionosphere. • The corrected differential message is then broadcast through one of two geostationary satellites, and is then received by a WAAS-capable GPS receiver.

33. Accuracy – Differential GPS • Provides high accuracy for a small area • Uses a local ground station transmitter • Accuracy can be better than one inch

34. Limitations • Requires good line-of-sight to satellites • May occasionally have difficulty using GPS in vehicles • Generally unusable inside a building (or cave)

35. Other concerns • GPS can be subject to accidental and intentional interference • Easily jammed using strategically placed low-power transmitters • WAAS is also at risk • Selective Availability (SA) or SCATANA could be instituted during a national emergency (but this is unlikely) • Current plan calls for possible use of “Selective Denial” where GPS is degraded or denied to specific geographic areas

36. Gotchas • True vs. Magnetic directions (a configuration option in some units) • The Apollo GX 55 will always use magnetic directions • Batteries! • The need for training and practice • Expressing coordinates • Seconds vs. Decimal Minutes

37. Terminology • Describing places • Describing directions

38. Terminology: Waypoint • A specific named location either defined by the user or defined in the instrument’s database • Waypoints sometimes come in flavors: • User defined waypoints • Built-in database waypoints (example: an airport)

39. Terminology:Defining Different Directions • Desired Track / Course • Bearing • Track • Heading ** In general, you should take note whether your GPS is giving you directions as True or Magnetic directions ** The GX-55 always gives Magnetic directions

40. Describing LocationsA Choice to Understand • We describe latitude and longitude normally using degrees and minutes • When dealing with fractions of minutes there is, however, a choice • There are essentially two options: • One can use seconds (of which there are 60 in one minute) • One can use decimal-minutes (i.e. tenths and hundredths of a minute) • Many GPS units can be configured to display one way or the other

41. Describing LocationsYet another option • Sometimes, latitude and longitude are expressed in degrees only. • Thus the following are equivalent expressions of longitude: • 93o 20’ 00” • 93.33333o

42. Describing LocationsCAP Standard Method • The standard we will use in CAP is degrees and decimal minutes • Example: 45 degrees 35.4 minutes North 93 degrees 42.2 minutes West • This is the standard way the Air Force provides coordinates to us for search and rescue • This is also the way our GX-55 normally displays position information • In CAP we will not usually use “seconds” unless working with another agency that wishes to do so.

43. Describing Locations:Communicating with Others • The seconds vs. decimal minutes question is a big source of confusion even within single organizations • Some people erroneously say “seconds” when they mean “hundredths of a minute” • Some people say “point” or “decimal” when they should have said “minutes” and “seconds” • Take nothing for granted when getting information • Be accurate and clear when giving information • Especially when working with other-agencies, triple-check all coordinates to make sure we’re all speaking the same language • Some organizations normally uses Degrees-Minutes-Seconds as their standard way of describing positions, but they will use the word “decimal” or “point” to separate the three parts of the coordinate

44. Describing LocationsYet Another Approach to be Aware of • Some GPS units also offer the option to display position information using Universal Transverse Mercator” (UTM) • An alternative to using degrees and minutes • Beyond the scope of this course

45. GX-55 Search patterns • Describing the patterns • Parallel Line (Grid) • Creeping Line • Expanding Square • Route and offset route

46. 414 B A 445 446 D C MSP 413 A o o o o o o 93 45’ 45 30’ N 93 30’ W 94 00’ W 45 45’ 46 00’ N Parallel Line Search Patterna.k.a. “Grid Search” • “US Grids” are areas 15 minute to a side, serially numbered for each sectional chart (MSP means “Twin Cities” sectional) • 7.5 minute quarter grids are named A, B, C, and D – in reading order, left to right, top to bottom

47. o o o o 94 00’ W 93 52.5’ W 45 52.5’ N 46 00’ N Parallel Line Search Patterna.k.a. “Grid Search” • The GPS unit labels the four corners (and also four search pattern entry points) 1, 2, 3, and 4 – clockwise starting in northwest. 1 2 MSP 413 A 4 3

48. Describing a Parallel Line Pattern • Grid identifier and starting waypoint (i.e. corner of quarter-grid) • Track spacing • Direction of tracks – either E/W or N/S Note: Search area for a parallel line pattern in the GX55 is always a quarter-grid

49. Parallel Line Pattern Example • Quarter Grid MSP 413A1 • Northwest corner of grid MSP 413A • Track spacing 1 NM • Tracks running east to west MSP 413 A Track spacing

50. Creeping Line Search Pattern • Shaped much like a parallel line pattern, but with legs aligned perpendicular to a route (rather than by ordinal directions) • Descriptive parts: • Starting point (any waypoint) • Direction • Starting left or right side • Track spacing • Leg length • Number of legs Direction Track spacing Leg length Starting Waypoint Starting on left side