RADIO NAVIGATION REVISION QUESTIONS Flashcards
(236 cards)
1
Q
- When would VDF be used for a position fix?
A
When declaring an emergency on 121.500 MHz
2
Q
- What equipment does an aircraft need when carrying out a VDF letdown?
A
VHF radio
3
Q
- Which of the following is an advantage of a VDF let down?
A
Only a VHF radio is needed in the aircraft
4
Q
- What is the maximum range at which a VDF station at 325 ft can provide a service to an aircraft at FL080?
A
134 nm
5
Q
- Which of the following statements regarding VHF direction finding (VDF) is most accurate?
A
It uses line of sight propagation
6
Q
- What is the wavelength corresponding to a frequency of 375 kHz?
A
800 m
7
Q
- A NDB transmits a signal pattern which is:
A
omni-directional
8
Q
- The accuracy of ADF within the DOC by day is:
A
+/-5°
9
Q
- Given that the compass heading is 270°, the deviation is 2°W, the variation is 30°E and the relative bearing of a beacon is 316°, determine the QDR:
A
044
10
Q
- Two NDB’s, one 20 nm from the coast and the other 50 nm further inland. Assuming coastal error is the same for each, from which NDB will an aircraft flying over the sea receive the greatest error?
A
The NDB at 50 nm
11
Q
- Which of the following is likely to have the greatest effect on the accuracy of ADF bearings?
A
Interference from other NDB’s, particularly at night
12
Q
- Which of the following are all errors associated with ADF?
A
Mountain effect, station interference, static interference
13
Q
- What action must be taken to receive a bearing from an ADF?
A
Both the loop and sense aerials must receive the signal
14
Q
- When is coastal error at its worst for an aircraft at low level?
A
Beacon inland at an acute angle to the coast
15
Q
- A radio beacon has a range of 10 nm. By what factor should the power be increased to achieve a range of 20 nm?
A
4
16
Q
- Which of the following is the most significant error in ADF?
A
Static from Cb
17
Q
- Which of the following may cause inaccuracies in ADF bearings?
A
Lack of failure warning, station interference, static interference
18
Q
- The allocated frequency coverage of NDB’s is:
A
190 – 1750 kHz
19
Q
- The principle used to measure VOR bearings is:
A
phase comparison
20
Q
- When converting VOR and ADF bearings to true, the variation at the …… should be used for VOR and at the …… for ADF.
A
station, aircraft
21
Q
- An aircraft flies from a VOR at 61N 013W to 58N 013W. The variation at the beacon is 13W and the variation at the aircraft is 5W. What radial is the aircraft on?
A
193
22
Q
- In a conventional VOR the reference signal and the variable signal have a 30 Hz modulation. The variable signal modulation is produced by:
A
a 30 Hz rotation producing a 30 Hz modulation
23
Q
- If the VOR accuracy has a limit of 1.0°, what is the maximum cross track error at 200 nm?
A
3.5 nm
24
Q
- What is the maximum distance apart a VOR and TACAN can be located and have the same identification?
A
600m
25
25. What is the maximum distance between VOR beacons designating the centreline of an airway (10 nm wide), if the expected VOR bearing error is 5.5°?
109 nm
26
26. On a CVOR the phase difference between the AM and FM signals is 30°. The VOR radial is:
330
27
27. In a certain VORTAC installation the VOR is coding STN and the DME is coding STZ. This means that the distance between the two beacons is in excess of:
600m
28
28. Using a 5 dot CDI, how many dots would show for an aircraft on the edge of an airway at 100 nm from the VOR beacon?
1.5
29
29. The maximum range an aircraft at FL370 can receive transmissions from a VOR/DME at 800 ft is:
275 nm
30
30. When tracking a VOR radial inbound the aircraft would fly:
a great circle track
31
31. Which of the following is a valid frequency (MHz) for a VOR?
112.20
32
32. Using a VOR beyond the limits of the DOC may result in:
interference from other VOR’s operating on the same frequency
33
33. An aircraft is flying a heading of 090° along the equator, homing to a VOR. If variation at the aircraft is 10°E and 15°E at the VOR, what is the inbound radial?
255
34
34. When identifying a co-located VOR/DME the following signals are heard in the Morse code every 30 seconds:
4 identifications with the DME at a higher tone
35
35. What is the maximum range a transmission from a VOR beacon at 169 ft can be received by an aircraft at FL012:
60 nm
36
36. An aircraft is tracking inbound to a VOR beacon on the 105 radial. The setting the pilot should put on the OBS and the CDI indications are:
285, TO
37
37. When tracking the 090 radial outbound from a VOR, the track flown is:
a great circle
38
38. The frequency band of VOR is:
VHF
39
39. On which radial from a VOR at 61N025E (VAR 13°E) is an aircraft at 59N025E (VAR 20°E)?
167
40
40. What is the minimum height an aircraft must be to receive signals from a VOR at 196 ft amsl at a range of 175 nm?
16,000 ft
41
41. For a conventional VOR a phase difference of 090° would be achieved by flying ............... from the beacon:
East
42
42. At a range of 200 nm from a VOR, if there is an error of 1°, how far off the centreline is the aircraft?
3.5 nm
43
43. The quoted accuracy of VOR is valid:
at all times
44
44. Which of the following provides distance information?
DME
45
45. Which of the following would give the best indication of speed?
A DME on the flight plan route
46
46. What happens when a DME in the search mode fails to achieve lock-on?
It stays in the search mode, but reduces to 60 ppps after 15000 pulse pairs
47
47. The most accurate measurement of speed by DME for an aircraft at 30,000 ft will be when the aircraft is:
tracking away from the beacon at 100 nm
48
48. A DME beacon will become saturated when more than about ............... aircraft are interrogating the transponder.
100
49
49. A typical DME frequency is:
1000 MHz
50
50. The DME in an aircraft, cruising at FL210, fails to achieve lock on a DME at msl at a range of 210 nm. The reason for this is:
the aircraft is beyond line of sight range
51
51. The aircraft DME receiver accepts replies to its own transmissions but rejects replies to other aircraft transmissions because:
the PRF of the interrogations is unique to each aircraft
52
52. When an aircraft at FL360 is directly above a DME, at mean sea level, the range displayed will be:
6 nm
53
53. A DME frequency could be:
1000 MHz
54
54. An aircraft at FL360 is 10 nm plan range from a DME. The DME reading in the aircraft will be:
11.7 nm
55
55. A DME transceiver does not lock onto its own reflections because:
the interrogation and reply frequencies differ
56
56. What information does military TACAN provide for civil aviation users?
DME
57
57. The DME in an aircraft flying at FL430 shows a range of 15 nm from a beacon at an elevation of 167 ft. The plan range is:
13.5 nm
58
58. What are the DME frequencies?
960 – 1215 MHz
59
59. The time from the transmission of the interrogation pulse to the receipt of the reply from the DME ground station is 2000 microseconds (ignore the delay at the DME). The slant range is:
165 nm
60
60. The DME counters are rotating continuously. This indicates that:
the DME is trying to lock onto range
61
61. On a DME presentation the counters are continuously rotating. This indicates:
the DME is in the search mode
62
62. An aircraft at FL200 is 220 nm from a DME at msl. The aircraft equipment fails to lock on to the DME. This is because:
the aircraft is too low to receive the signal
63
63. On an ILS approach you receive more of the 90 Hz modulation than the 150 Hz modulation. The action you should take is:
fly right and down
64
64. The errors of an ILS localiser (LLZ) beam are due to:
ground reflections
65
65. The amplitude modulation of the ILS outer marker is ............... and it illuminates the ................ light in the cockpit.
400 Hz blue
66
66. The principle of operation of the ILS localiser transmitter is that it transmits two overlapping lobes on:
the same frequency with different amplitude modulations
67
67. The ILS glideslope transmitter generates false glidepaths because of:
multiple lobes in the radiation pattern
68
68. A category III ILS system provides accurate guidance down to:
the surface of the runway
69
69. A HSI compass rose is stuck on 200°. When the aircraft is lined up on the centreline of the ILS localiser for runway 25, the localiser needle will be:
centred
70
70. The coverage of the ILS glideslope with respect to the localiser centreline is:
+/-8° to 10 nm
71
71. The middle marker is usually located at a range of ................., with an audio frequency of ................ and illuminates the ................. light.
1 km, 1300 Hz, amber
72
72. The sequence of marker colours when flying an ILS approach is:
blue, amber, white
73
73. The sensitive area of an ILS is the area aircraft may not enter when:
category II/III ILS operations are in progress
74
74. The ILS localiser is normally positioned:
300 m from the upwind end of the runway
75
75. The audio frequency of the outer marker is:
400 Hz
76
76. An aircraft is flying downwind outside the coverage of the ILS. The CDI indications will be:
unreliable in azimuth and elevation
77
77. The frequency band of the ILS glidepath is:
UHF, decimetric
78
78. In which band does the ILS glidepath operate?
UHF, decimetric
79
83. Primary radar operates on the principle of:
pulse technique
80
84. The definition of a radar display will be best with:
narrow beamwidth and narrow pulsewidth
81
85. The main advantage of a continuous wave radar over a pulsed radar is:
removes the minimum range restriction
82
86. Which of the following systems use pulse technique?
1. secondary surveillance radar
2. airborne weather radar
3. distance measuring equipment
4. primary radar
all the above
83
87. To double the range of a primary radar, the power must be increased by a factor of:
16
84
88. In a primary pulsed radar the ability to discriminate in azimuth is a factor of:
beamwidth
85
89. The maximum range of a ground radar is limited by:
pulse recurrence rate
86
90. What does pulse recurrence rate refer to?
the number of pulses per second
87
91. The maximum PRF required for a range of 50 nm is:
1620 pps
88
92. The best radar for measuring very short ranges is:
a continuous wave primary radar
89
93. Which is the most suitable radar for measuring short ranges?
continuous wave primary
90
94. The main advantage of a slotted scanner is:
reduces sidelobes and directs more energy into the main beam
91
95. The maximum unambiguous (theoretical) range for a PRF of 1200 pps is:
67 nm
92
96. The PRF of a radar is 450 pps. If the speed of light is 300000 kps, what is the maximum range of the radar?
333 km
93
97. The best picture on a primary radar will be obtained using:
short wavelength, narrow beam
94
98. Which of the following is a primary radar system?
AWR
95
99. On what principle does primary ATC radar work?
pulse technique
96
100. ATC area surveillance radars will normally operate to a maximum range of:
300 nm
97
101. An area surveillance radar is most likely to use a frequency of:
600 MHz
98
102. Short range aerodrome radars will have ............... wavelengths.
centimetric
99
103. The ASMR operates in the ............... band, the antenna rotates at ................ rpm can ............... distinguish between aircraft types.
SHF, 60, sometimes
100
104. The frequency band of most ATC radars and weather radars is:
SHF
101
105. The airborne weather radar (AWR) cannot detect:
snow
102
106. The frequency of AWR is:
9375 MHz
103
107. The use of the AWR on the ground is:
permitted provided special precautions are taken to safeguard personnel and
equipment
104
108. Which type of cloud does the AWR detect?
Cumulus
105
109. The AWR uses the cosecant squared beam in the ............... mode.
MAP
106
110. On the AWR display the most severe turbulence will be shown:
by a steep colour gradient
107
111. On an AWR colour display, the sequence of colours indicating increasing water droplet size is:
green, yellow, red
108
112. In an AWR with a 5° beamwidth, how do you orientate the scanner to receive returns from clouds at or above your level?
2.5° uptilt
109
113. The ISO-ECHO circuit is incorporated in the AWR:
to display areas of turbulence in cloud
110
114. The main factors which affect whether an AWR will detect a cloud are:
the size of the water droplets and the range of the cloud
111
115. In an AWR with a colour CRT, areas of greatest turbulence are indicated by:
most rapid change of colour
112
116. With the AWR set at 100 nm range a large cloud appears at 50 nm. If the range is reduced to 50 nm:
the image will increase in area and move to the top of the screen
113
117. As a storm intensifies, the colour sequence on the AWR display will change:
green, yellow, red
114
118. The cosecant squared beam is used for mapping in the AWR because:
a larger area of ground is illuminated by the beam
115
119. On switching on the AWR a single line appears on the display. This means that:
the antenna is not scanning
116
120. The AWR can be used on the ground provided:
1. the aircraft is clear of personnel, buildings and vehicles
2. conical beam is selected
3. maximum uptilt is selected
4. the AWR must never be operated on the ground
1, 2 and 3
117
121. Doppler navigation systems use ............... to determine the aircraft groundspeed and drift.
frequency shift in signals reflected from the ground
118
122. Which axes is the AWR stabilised in?
Pitch and roll
119
123. With normal SSR mode C altitude coding the aircraft replies by sending back a train of up to 12 pulses contained between 2 framing pulses with:
4096 codes in 4 blocks
120
124. Why is the effect of returns from storms not a problem with SSR?
SSR does not use the echo principle
121
125. The advantages of SSR mode S are:
data link, reduced voice communications
122
127. The accuracy of SSR mode C altitude as displayed to the air traffic controller is:
+/-50 ft
123
128. The SSR ground transceiver interrogates on ................ and receives responses on ................
1030 MHz, 1090 MHz
124
129. The vertical position provided by SSR mode C is referenced to:
1013.25 HPa
125
130. Why is a secondary radar display free from weather clutter?
The principle of the return of echoes is not used
126
131. The availability of 4096 codes in SSR is applicable to mode:
a. A.
b. C.
c. S.
d. all.
all
127
132. With reference to SSR, what code is used to indicate transponder altitude failure?
0000
128
136. In NAVSTAR/GPS the PRN codes are used to:
determine satellite range
129
137. The MDA for a non-precision approach using NAVSTAR/GPS is based on:
barometric altitude
130
138. If, during a manoeuvre, a satellite being used for position fixing is shadowed by the wing, the effect on position will be:
the position will degrade
131
139. The time required for a GNSS receiver to download the satellite almanac for the NAVSTAR/GPS is:
12.5 minutes
132
140. The effect of the ionosphere on NAVSTAR/GPS accuracy is:
minimised by the receivers using a model of the ionosphere to correct the signals
133
141. The height derived by a receiver from the NAVSTAR/GPS is:
above the WGS84 ellipsoid
134
142. The NAVSTAR/GPS constellation comprises:
24 satellites in 6 orbits
135
143. Selective availability may be used to degrade the accuracy of the NAVSTAR/GPS position. This is achieved by:
random dithering of the broadcast satellites clock time
136
144. The positioning of a GNSS aerial on an aircraft is:
on top of the fuselage close to the centre of gravity
137
145. The NAVSTAR/GPS space segment:
provides X, Y, Z & T co-ordinates and the constellation data
138
146. Concerning NAVSTAR/GPS orbits, which of the following statements is correct?
a. The inclination of the orbits is 55° with an orbital period of 12 hours.
b. The inclination of the orbits is 55° with an orbital period of 24 hours.
c. The orbits are geostationary to provide global coverage.
d. The orbits are inclined at 65° with an orbital period of 11 hours 15 minutes.
The inclination of the orbits is 55° with an orbital period of 12 hours
139
147. NAVSTAR GPS receiver clock error is removed by:
adjusting the pseudo-ranges to determine the error
140
148. The contents of the navigation and systems message from NAVSTAR/GPS SVs include:
satellite clock error, almanac data, ionospheric propagation information
141
149. The NAVSTAR/GPS segments are:
space, control, user
142
150. The preferred GNSS receiver for airborne application is:
multi-channel
143
151. The orbital height of geostationary satellites is:
35800 km
144
152. The best accuracy from satellite systems will be provided by:
NAVSTAR/GPS and GLONASS
145
153. The azimuth and elevation of the satellites is:
determined by the receiver from the satellite almanac data
146
154. The skysearch carried out by a GNSS receiver:
involves the receiver downloading the almanac from each satellite before determining
which satellites are in view
147
155. An aircraft GNSS receiver is using 5 satellites for RAIM. If the receiver deselects one satellite then the flight should be continued:
using alternative navigation systems
148
156. The WGS84 model of the earth is:
a geoid
149
157. The frequency band of the NAVSTAR/GPS L1 and L2 frequencies is:
UHF
150
158. The number of satellites required to produce a 4D fix is:
4
151
159. How many satellites are needed for a 2D fix?
3
152
160. Which of the following statements concerning ionospheric propagation errors is true?
a. They are significantly reduced by the use of RAIM.
b. They are eliminated using differential techniques.
c. They are significantly reduced when a second frequency is available.
d. Transmitting the state of the ionosphere to the receivers enables the error to reduced to
less than one metre.
They are significantly reduced when a second frequency is available
153
161. Using differential GNSS for a non-precision approach, the height reference is:
barometric
154
162. The number of satellites required to provide a 3D fix without RAIM is:
4
155
163. The number of satellites required for a fully operational NAVSTAR/GPS is:
24
156
164. ‘Unauthorised’ civilian users of NAVSTAR/GPS can access:
the C/A code
157
165. When using GPS to fly airways, what is the vertical reference used?
Barometric
158
166. The nav/system message from GLONASS and NAVSTAR/GPS is found in the ............... band.
UHF
159
168. During flight using NAVSTAR/GPS and conventional navigation systems, you see a large error between the positions given by the systems. The action you should take is:
continue using the conventional systems
160
169. What information can a GPS fix using four satellites give you?
Latitude, longitude, altitude and time
161
170. What are the basic elements transmitted by NAVSTAR/GPS satellites?
offset of the satellite clock from GMT
ephemeris data
ionospheric delays
162
171. What is the purpose of the GPS control segment?
To monitor the satellites in orbit
163
172. In GNSS a fix is obtained by:
measuring the time taken for signals from a minimum number of satellites to reach the aircraft
164
173. The inclination of a satellite is:
the angle between the SV orbit and the equator
165
174. How is the distance between the NAVSTAR/GPS SV and the receiver determined?
By measuring the time from transmission to reception and multiplying by the speed of
light
166
175. The distance measured between a satellite and a receiver is known as a pseudo-range because:
it includes receiver clock error
167
176. The task of the control segment is to:
monitor the SV ephemeris and clock
168
177. To provide 3D fixing with RAIM and allowing for the loss of one satellite requires ............... SVs:
6
169
178. In NAVSTAR/GPS the PRN codes are used to:
differentiate between satellites
170
179. An ‘all in view’ satellite navigation receiver is one which:
selects and tracks all (in view) satellites and selects the best four
171
180. Which GPS frequencies are available for commercial air transport?
1575.42 MHz only
172
182. In GPS on which frequencies are both the C/A and P codes transmitted?
The higher frequency
173
183. The orbits of the NAVSTAR GPS satellites are inclined at:
55° to the plane of the equator
174
184. RAIM is achieved:
within the receiver
175
185. The function of the receiver in the GNSS user segment is to:
track the satellites to calculate range
176
186. In which frequency band are the L1 and L2 frequencies of GNSS?
UHF
177
187. Which of the following statements concerning differential GPS (DGPS) is true?
DGPS can improve the accuracy of SA affected position information
178
188. The visibility of GPS satellites is:
dependent on the location of the user
179
189. In the approach phase with a two dot lateral deviation HSI display, a one dot deviation from track would represent:
0.5°
180
190. The required accuracy of a precision RNAV (P-RNAV) system is:
1 nm standard deviation or better
181
191. The ETA generated by the FMS will be most accurate:
if the groundspeed and position are accurate
182
192. When is the FMS position likely to be least accurate?
TOD
183
193. For position fixing the B737-800 FMC uses:
DME/DME
184
194. When using a two dot HSI, a deviation of one dot from the computed track represents:
2 nm
185
195. An aircraft, using a 2D RNAV computer, is 12 nm from the phantom station, 25 nm from the VOR/DME designating the phantom station and the phantom station is 35 nm from the VOR/ DME. The range read out in the aircraft will be:
12 nm
186
196. The FMC position is:
computer generated from the IRS and radio navigation positions
187
201. When midway between two waypoints, how can the pilot best check the progress of the aircraft?
By using the computed ETA for the next waypoint
188
202. Which of the following can be input manually to the FMC using a maximum of 5 alphanumerics?
Navigation facilities, reporting points, airways designators
189
203. The inputs to the EHSI display during automatic flight include:
IRS, FMC and radio navigation facilities
190
The inputs the pilot will make to the FMC during the pre-flight initialisation will include:
planned route, aircraft position, and departure runway
191
209. In the NAV and EXP NAV modes one dot on the EHSI represents:
2 nm
192
210. The phantom station in a 2D RNAV system may be generated by:
VOR/DME
193
211. The operation of a 2D RNAV system may be seriously downgraded:
because the computer cannot determine if the aircraft is within the DOC of the programmed facilities
194
216. The FMS database can be:
only read by the pilots
195
220. In the B737-400 EFIS which component generates the visual display?
Symbol generator
196
221. When is the IRS position updated?
On the ground only
197
226. The navigation database in the FMS:
is read only
198
228. In an EHSI the navigation information comes from:
FMC, radio navigation
199
230. According to ICAO (Annex 11), the definition of an RNAV system is:
one which enables the aircraft to navigate on any desired flight path within the coverage of appropriate ground based navigation aids or within the specified limits of self contained on-board systems or a combination of the two
200
231. Which of the following is independent of external inputs?
a. INS.
b. Direct reading magnetic compass.
c. VOR/DME.
d. ADF.
INS
201
232. The track line on an EFIS display indicates:
the actual aircraft track over the ground, which will coincide with the aircraft heading
when there is zero drift
202
234. The EHSI is showing 5° fly right with a TO indication. The aircraft heading is 280°(M) and the required track is 270°. The radial is:
095
203
235. On the B737-400 EHSI what happens if the selected VOR fails?
The deviation bar is removed
204
236. In an RNAV system which combination of external reference will give the most accurate position?
Rho/rho
205
237. If the signal from a VOR is lost, how is this shown on the B737-400 EHSI display?
By removal of the deviation bar and pointer
206
238. The colour used on the B737-400 EHSI weather display to show turbulence is:
magenta
207
241. In order that a waypoint designated by a VOR can be used by a RNAV system:
the VOR need not be in range when input but must be when used
208
242. Which EHSI modes cannot show AWR information?
PLAN and FULL VOR/ILS/NAV
209
245. The NAVSTAR/GPS constellation comprises:
4 SVs each in 6 orbits
210
246. Comparing the L1 and L2 signals helps with the reduction of which GNSS error?
Ionospheric propagation
211
247. The normal maximum range for an ATC surveillance radar is:
250 nm
212
248. The cause of a RNAV giving erratic readings would be:
the aircraft is outside the DOC of the reference station
213
249. Flying an ILS approach with a 3° glideslope referenced to 50 ft above the threshold, an aircraft at 4.6 nm should be at an approximate height of:
1,450 ft
214
250. The height of the GPS constellation is:
20200 km
215
251. Which type of radar could give an indication of the shape and sometimes the type of the aircraft?
Aerodrome surface movement radar
216
253. The accuracy required of a basic area navigation (B-RNAV) system is:
+/-5 nm on 95% of occasions
217
254. What function does the course line computer perform?
Uses VOR/DME information to determine track and distance to a waypoint
218
255. The emissions from a non-directional beacon (NDB) are:
omni-directional
219
256. How does night effect affect ADF?
Skywave interference which affects the null and is worst at dawn and dusk
220
257. What is an ADC input to the FMC?
TAS
221
258. A typical frequency for DME would be:
1200 MHz
222
259. When flying under IFR using GPS and a multi-sensor system:
the multi-sensor system must be operating and its information displayed
223
260. The indications from a basic RNAV are behaving erratically. The reason is likely to be:
the aircraft is outside the DOC of the reference VOR/DME
224
261. What is the maximum PRF that allows detection of targets to a range of 50 km? (ignore any flyback time).
3000 pps
225
262. In NAVSTAR/GPS the space segment:
provides the positional information to the receiver
226
263. An accurate position fix on the EHSI will be provided by inputs of:
FMC, IRS, radio navigation aids
227
264. The almanac in the receiver:
is used to determine which satellites are above the horizon
228
265. In a RNAV system the DME is tuned:
by selecting DMEs to give suitable angle of cut to get a fix automatically
229
266. Which input to the FMC is taken from sources external to the aircraft?
VOR/DME
230
267. In NAVSTAR/GPS range measurement is achieved by measuring:
the time taken for the signal to travel from the satellite to the receiver
231
268. Quadrantal error in the ADF is caused by:
the electrical wiring running through the aircraft
232
269. For the FMC the take-off speeds, V1, VR and V2 are found:
in the performance database
233
270. The optimum climb and descent speeds used byn the FMC are found:
in the performance database
234
271. The optimum cruise speeds used by the FMC are found:
in the performance database
235
272. Which of the following external inputs is required by the FMC to determine W/V?
a. Magnetic heading.
b. Mach no.
c. TAS.
d. Track and groundspeed.
TAS
236
273. Which of the following is true concerning the use of GNSS position in the FMC?
a. It is used to verify and update the IRS position.
b. An alternate source of position must be used and displayed.
c. GNSS position is usable stand alone.
d. GNSS data may only be used in the absence of other positional information.
An alternate source of position must be used and displayed
