Questions tagged [gnss]

GNSS is a global satellite navigation system. GPS is the US GNSS.

Filter by
Sorted by
Tagged with
9 votes
5 answers
475 views

Do GPS coordinates of a fixed point in space ever change?

As I understand, GNSS uses the WGS84 model of the earth to pin-point points in 3D space. However, once the GPS coordinates of a point in space have been determined (say a GPS waypoint), do it's ...
PapaMike99's user avatar
0 votes
1 answer
125 views

Passenger GNSS lock during ascent and descent

When flying on commercial flights for the past several years I've used GNSS on my smartphone to track my location for fun. The signal strength in the cabin isn't ideal, but it's generally good enough ...
Altay_H's user avatar
  • 103
0 votes
1 answer
82 views

Difference between accuracy, integrity, availability, continuity, and functionality

My understanding is that accuracy is how close my estimated position is to my actual position at a certain point in time. I don't really understand how integrity is different from accuracy. Continuity ...
Name's user avatar
  • 886
1 vote
1 answer
104 views

How to update the navigation database on a Garmin GPS 165 TSO?

What is the update process for updating GPS 165 TSO. The updates are available on shop.jeppesen however, how to transfer them to this GPS ??
user avatar
1 vote
1 answer
207 views

Approach miniumum when I lost WAAS during approach

I have a GPS receiver with WAAS. During an LPV approach, I received an LOI message That means I only lost WAAS, not RAIM. Did I just need to change minimum to LNAV and continue the approach?
sophie's user avatar
  • 11
0 votes
1 answer
125 views

IFR plan only with GPS

I'm right before CFII checkride I understand that if it is without WAAS, I need navigational equipment other than GPS because I can flight plan based on GPS either destination or alternate. However, ...
agentpilot's user avatar
1 vote
1 answer
82 views

Data for mapping a past flight?

Is there a website that shows past flight tracks of a few days back? tells how to use FlightAware to see a past flight on a map.  But is there any public source of times/coordinates for past flights? ...
WGroleau's user avatar
  • 247
2 votes
2 answers
426 views

Is the GPS ground track true or magnetic?

This question arises from the Garmin GPS units (eg. GNS530 or GTN750), but the term ground track appears in a general context of GPS units so my question is also general. Is the ground track (TRK in ...
J.Lewandowski's user avatar
15 votes
6 answers
8k views

Why don't planes (mostly airliners) primarily use GPS for navigation?

For the four airliners that I use in Microsoft Flight Simulator (A320neo, A319, A310-300, and 747-8I), I always have to align IRS and set up RAD NAV on the MCDU. Why can't we just use GPS? On the 747, ...
DaCuteRaccoon's user avatar
5 votes
2 answers
2k views

How is TSO C145 equipment different from TSO C146 equipment?

From the AIM1-1-18 c1) C145 - "Airborne Navigation Sensors Using the GPS Augmented by the Wide Area Augmentation System" C146 - "Stand-Alone Airborne Navigation Equipment Using the ...
Name's user avatar
  • 886
5 votes
2 answers
792 views

What is the difference between SBAS and SBAS PA mode on my FMS?

We have a Collins FMS, and in the GNSS control page it tells you what mode it is operating in. In the instance that I checked it, it said "SBAS PA". The flight manual said that it can ...
Name's user avatar
  • 886
18 votes
4 answers
6k views

If a GPS displays the correct time, can I trust the calculated position?

Suppose I plan to reactivate an airplane that has been stored in a boneyard for a year or two, or at least power it up and turn on the avionics. Also suppose for the sake of the question that the GPS ...
Steve V.'s user avatar
  • 23.2k
1 vote
0 answers
49 views

RAIM Checks when using GNSS in lieu of DME for distance information

I understand that a RAIM has to be checked on the ground as part of preflight, as well as before the commencement of an RNAV/RNP approach. What I am unable to find information on online, is whether a ...
Zhi Hao Tan's user avatar
4 votes
1 answer
814 views

GNSS approaches: Why does LNAV minima even exist? Wouldn't all aircraft fly to LNAV/VNAV or LPV minimums?

I am new to instrument flying and am trying to wrap my head around the different types of GNSS approach minimums. I am having an issue understanding why LNAV minimums exist. My understanding is, if ...
foxtrottrotfox's user avatar
4 votes
1 answer
292 views

What does it mean for a GPS PRN to be unserviceable?

There is a current NOTAM: !GPS 02/035 GPS Navigation PRN 28 unserviceable Feb 21, 2023 2020Z to May 31, 2023 2359Z What exactly does it mean for a GPS PRN to be unserviceable, and what significance ...
Chris's user avatar
  • 15.5k
0 votes
1 answer
106 views

Does Garmin G300 GPS use true heading or magnetic?

Does Garmin G300 GPS use true heading or magnetic? Sorry couldn't find this information anywhere else.
Shuheng Zheng's user avatar
5 votes
3 answers
2k views

Why should the optimum position of GPS Antenna be close to aircraft's CG?

In CAE OAA Book11-Radio Navigation Chapter-18 Page-318, under GPS Error, "The optimum position for the antenna is on top of the fuselage close to the aircraft's centre of gravity". In the ...
Krishna Kanth's user avatar
0 votes
3 answers
3k views

What do ENR,TERM and APR mean in the HSI? Also how may I call this part on the HSI?

How should I answer when my instructor asks me what it means during the flight? I searched but couldn't find a definitive answer.
pilot162's user avatar
  • 2,195
1 vote
0 answers
269 views

Along Track Distance ATD

ATD (Along-Track Distance) is used by ATC for certain types of (rare) NON-Radar Separation. I am training as an Air Traffic Controller in the USA. I have been told the only way to know if an aircraft ...
user64263's user avatar
6 votes
1 answer
272 views

How to reduce the volume of the GTN750 traffic warning beep?

We've got a GTN 750 with ADS-B IN and OUT. When we encounter traffic it emits a high pitched pulsing beep. It cannot be muted by any means - say you are on final and there's an aircraft holding short ...
ExternalUse's user avatar
8 votes
1 answer
438 views

Do GPS systems in modern avionics mitigate against spoofing attacks?

There exist a number of different techniques [PDF] to mitigate (or at least detect) GPS spoofing, but the most effective techniques require access to the military-only M-code [PDF]. However, there was ...
forest's user avatar
  • 226
15 votes
4 answers
5k views

Do airlines use GPS for critical purposes? If so, why?

It is being reported that airlines in Finland have noticed interference with their GPS signals near Russia. This is causing them to be unable to land at at least one airport: Lithuanian airline ...
User65535's user avatar
  • 309
3 votes
1 answer
5k views

How to track a flight that I am flying in using the GPS antenna in my mobile phone (without internet)?

I am in India. I booked my first flight ticket a few weeks ago and am very interested in identifying locations as well as geographical and human structures that I will see. I have downloaded many GB's ...
Ritesh Singh's user avatar
19 votes
3 answers
21k views

What are satellite time, GPS time, and UTC time?

What is the difference between Satellite time, GPS time and UTC time? How are these calculated from one another?
Sourabh Jain's user avatar
5 votes
1 answer
590 views

What does a DME indicator do in HOLD or RNAV mode?

I found this DME indicator on the Cessna 210. Its mode switch has four positions - NAV1, NAV2, RNAV and HOLD. NAV1 and 2 are clear - it uses the NAV1 and 2 freq respectively. I'm wondering what the ...
TheEagle's user avatar
  • 1,394
0 votes
1 answer
2k views

Can single engine/smaller aircraft turn off ADS-B?

I was just looking at the adsbexchange website, and was wondering if it was possible for smaller, private aircraft to turn off their ADS-B? I was wondering this because id figure that maybe not ...
Obama. The real obama.'s user avatar
2 votes
1 answer
400 views

Do the regulations allow DME from an expired IFR-certified GPS with an out of date database to be used for this ILS approach under an IFR plan?

Since we cannot fly an RNAV approach with out of date GPS database, the approach in question is KCRE ILS 23. Whether it was asking for V2F or the full approach starting from ASHES (which is 18.5 DME ...
saigafreak's user avatar
7 votes
1 answer
2k views

How does drone reliance on GPS make it 'semi-stealthy'?

I saw this on CNN today. For months, US intelligence and military personnel in Iraq have been raising alarms about the risk to American forces from these newer, more sophisticated Iranian-made drones....
Cascabel_StandWithUkraine_'s user avatar
5 votes
1 answer
895 views

Why do some GPS receivers suppress RAIM integrity warnings after you pass the FAF?

RAIM performs an integrity check 2NM from the FAF. If RAIM is lost before the FAF, one should execute the missed approach. However, if RAIM is lost after passing the FAF, some GPS receivers will ...
JoeyMo's user avatar
  • 51
1 vote
1 answer
311 views

Why are SBAS-equipped planes exempt from the preflight prediction check?

My question stems from this other question: Why is training regarding the loss of RAIM given so much more emphasis than training regarding the loss of SBAS? Two answers say losing RAIM puts a question ...
user avatar
6 votes
2 answers
1k views

Why weren't SA-On GPS units updated to become SA-Aware?

SA = Selective Availability (gps.gov) SA-On and SA-Aware are widely used in current air transport aircraft (...) GPS that behave as if SA is still active (SA-On) GPS that behave as if SA has been ...
user avatar
0 votes
3 answers
574 views

What kind of airspeed does a (3D) GPS measure?

Assuming a GPS receiver is advanced enough to compute 3D position/velocity with reasonable accuracy, it can indicate not only the aircraft's ground speed (which ignores altitude changes), but ...
anrieff's user avatar
  • 109
-4 votes
1 answer
139 views

Find the course or heading of an object [closed]

Im working with orientation using GPS + IMU, and before the actual implementation of the program, im working with simulation using a dataset that provides me some GPS data, such as latitude, longitude,...
Bruno Otavio's user avatar
10 votes
2 answers
4k views

Why is training regarding the loss of RAIM given so much more emphasis than training regarding the loss of SBAS?

I've noticed a lack of subject matter on the loss of SBAS as compared to RAIM. In the ACS there is mention of RNP, SBAS (WAAS), and RAIM, which are all related, but the available content for RAIM and ...
Ryan Mortensen's user avatar
-3 votes
2 answers
348 views

What is the purpose of aircraft localization? [closed]

I want to understand what is the purpose of doing localization while an aircraft is flying? What sensors are used by the instruments that do this localization of an aircraft? Is there more than one ...
scico111's user avatar
  • 155
7 votes
2 answers
6k views

Why RNAV SIDs and STARs are RNAV 1 instead of RNP 1?

I am studying for my CFII check-ride and I was wondering to know why SIDs and STARs are not RNP 1 but RNAV 1? Let's start with the following two definitions RNP - Required Navigation Performance: It's ...
Ivan Parra's user avatar
0 votes
1 answer
284 views

Is it possible to export NMEA data from a Garmin GDL-39 to a custom Android App?

Hi I was wondering if it's possible to receive NMEA data from a Garmin GDL 39 on an Android device (preferred over Bluetooth) as I can't find any information out there on it.
pwned555's user avatar
  • 103
0 votes
1 answer
492 views

What is the meaning of GPS IAP RNP that appears in Notes?

Referring to the RNAV (GPS) RWY 30 approach, what is the meaning of RNP APCH in the notes section? (Highlighted in YELLOW) Also, what are the separate DA values in parenthesis? (Highlighted with a red ...
dawg's user avatar
  • 937
3 votes
1 answer
439 views

In RTCA DO-260B, what were the reasons GVA was added ? Is it a replacement for something?

After digging up and reading through many documents, I have a rough picture of the evolution of DO-260 versions, particularly for its ADS-B Quality Indicators. For instance, in DO-260 (Version 0) ...
Agha's user avatar
  • 137
8 votes
1 answer
167 views

Due to the corrective calculations being ground-based, does the reliability of WAAS degrade with increases in altitude?

Since the WAAS system utilizes stations at known, fixed locations on the ground to make determinations for positional correction, is there a loss in the precision or validity of that correction with ...
Ryan Mortensen's user avatar
4 votes
1 answer
340 views

Why do ADS-B outages occur without simultaneous RAIM outages?

If you check the ADS-B prediction tool and the RAIM prediciton tool on SAPT.FAA.GOV you will see far more ADS-B outages. What causes ADS-B outages to occur at different times than RAIM outages? Are ...
Ryan Mortensen's user avatar
1 vote
1 answer
115 views

Is it possible to determine if winds were high without groundspeed, wind speed, AoA or AoS?

I have a data set that includes TAS, IAS, GPS Lat/Lon, Inertial Lat/Lon, ENU speed, inertial speeds, attitude, and accelerations. I don't need to know the exact wind speed, and I don't think that's ...
synchh's user avatar
  • 131
2 votes
3 answers
2k views

Are helicopter pilots required to use GPS navigation?

Some helicopter crashes are caused by a disoriented pilot. This would presumably be impossible with a GPS with terrain maps. Are pilots required to use a GPS when flying a helicopter in the US?
Xavier's user avatar
  • 139
0 votes
1 answer
492 views

What's the difference between a Sole Means Navigation System and a Primary Means Navigation System? [closed]

For bonus points, how you define a supplemental means navigation system?
rational-pi's user avatar
0 votes
0 answers
31 views

GPS Magnetic Declination and current database [duplicate]

Can I fly with an expired GPS database if I verify the waypoints locations? or is the magnetic declination part of the database?
Rozh Ali's user avatar
5 votes
1 answer
2k views

What is GPS HIL in layman's terms?

GNSS Horizontal Integrity Limit/ Horizontal Protection Level is a measure of GNSS position error/integrity that's very important in RNP operations and RAIM, but it has an obtuse definition in aviation ...
Cody P's user avatar
  • 6,773
1 vote
0 answers
284 views

What's the busiest airport that's not WGS-84 compliant?

Most latitude and longitude coordinates are defined relative to the WGS-84 standard, including GPS coordinates from your receiver. However, some coordinates are specified using local datums, and ...
Cody P's user avatar
  • 6,773
2 votes
1 answer
536 views

Does EASA allow using a portable GPS for RNAV capability?

Assume an older IFR-certified aircraft with the classical equipment, that is two VOR/ILS receivers with plain CDIs, ADF and DME, but no GPS. It can be flown IFR, but many routes can't be used, because ...
Jan Hudec's user avatar
  • 56.3k
1 vote
2 answers
2k views

Can a GPS waypoint be used when filing a VFR flight plan?

This probably equally applies to IFR flight plans, but the general question is can arbitrary (unrelated to an airway or named fix) GPS coordinates be used in the route on a flight plan?
hemp's user avatar
  • 579
3 votes
2 answers
184 views

Can jetliner pilots program departures when specific RNAV procedures do not exist?

Can commercial pilots (e.g. 737 and 737 Max) program departures into their on-board GPS navigation system for the first portion of a flight that doesn't have specific RNAV procedures?
FlyGRL's user avatar
  • 91