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Global Positioning System consists of a group of satellites that are used in conjunction with special purpose receivers to calculate a precise location. It is often used for aircraft navigation purposes.

15
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3answers
1k views

Are NDBs and VORs dying as a navigational method?

I am new to aviation, so bear with me on this question: I have read in multiple places that the VOR/NDB navigational aids are dying out to GPS. Is this true? Are more modern aircraft being built with ...
6
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1answer
130 views

If a SID chart says “GPS… required”, can the plane use a different GNSS?

This US/FAA standard instrument departure says "Note: GPS or DME/DME/IRU required." If the aircraft could tune into a different GNSS like GLONASS, could the pilot still legally fly the departure ...
4
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1answer
290 views

Why would a Mode-C transponder report a different altitude than an altimeter/GPS?

This is related to a small single-engined plane. On a recent flight, the controller kept telling me that I was 300 ft higher than it appeared on my altimeter and GPS (which were in sync). This was ...
5
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2answers
176 views

How can I tell a GPS installation is acceptable for IFR use?

I am evaluating an aircraft for use under IFR. I want to know if the GPS that is installed is acceptable for use under IFR. I have access to the logbooks and documentation. I want to check: That ...
2
votes
1answer
74 views

Position update rate of GPS [closed]

GPS satellites send data at the rate of 50 bits per second. One GPS subframe is 6 seconds long. How is it possible to update one's position faster than once in 30 seconds when we require the whole ...
3
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1answer
152 views

How do you program circular flight plans in GPS?

In a recent Buzzfeed article about aerial surveillance, I have seen a map showing perfectly circular flight patterns. Given how precise the patterns are, I highly doubt that the aircraft were being ...
2
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1answer
267 views

Is a non-WAAS Garmin 530 certified for an LNAV/VNAV approach?

I may not understand all the details of what I'm asking but trying to wrap my head around it. I am aware that before WAAS, some GPS aircraft were equipped to get vertical guidance by a Barocorrected ...
3
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2answers
206 views

Does the altitude or attitude of an aircraft affect GPS accuracy?

Of course we are assuming an effective signal is being received. I live near Idaho Falls, Idaho with a field elev of 5300ft. If I shoot an approach will GPS be more or less accurate then landing at ...
2
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1answer
117 views

Why is there a provision of pressure setting in GPS?

Some of the GPS have a provision of setting barometric pressure (QNH/QFE). How does it work?
49
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5answers
10k views

In the rare event that the U.S. DOD shuts off the GPS, what's the alternative?

In the U.S., the Department of Defense along with other Federal Agencies of the Government operates & maintains the GPS. In the rarest of the events, if for any reason whatsoever, the Government ...
9
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1answer
367 views

When should I start turning in this circling approach?

I've been practicing circling approaches in Homestead General Aviation Airport in Homestead, Florida (X51). I performed the RNAV (GPS) RWY 10 approach with circling minimums. My questions are: a) ...
1
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1answer
345 views

What are the WAAS requirements for RNAV (GPS) approaches?

Is a WAAS GPS required to fly in RNP airspace (e.g., RNAV (GPS) approaches)? Or, can you be approved to fly RNAV (GPS) approaches with, say a military EGI (embedded GPS/INS)?
3
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1answer
833 views

What are the lateral sensitivities of GPS approaches?

What are the lateral sensitivities of each of the WAAS and LNAV approach? Is the lateral sensitivity of WAAS the same as that of the localizer, which is 3 to 6 degrees? What about the LNAV approach?
0
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0answers
111 views

What is the correlation between RNP level and the CDI indication?

I got a question regarding the connection between RNP (required navigational performance) accuracy and cdi sensitivity of the HSI. According to the instrument flying handbook the standard for RNP on ...
3
votes
2answers
326 views

Can the iPad use GPS data from a Garmin aera 660?

Can the iPad use GPS data from a Garmin aera 660 portable GPS unit? I assume this would happen via Bluetooth, if it's possible. I would like the more accurate WAAS data from the Garmin for use with ...
4
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1answer
216 views

Why is there a GPS/RNAV waypoint co-located with a VOR?

There is an RNAV waypoint named STYCK co-located at what appears to be the exact location of the LOA VOR (coordinates match precisely as well). Why would the creation of a waypoint be necessary if IFR ...
7
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1answer
219 views

How can I check that the GPS receiver is sending data to the transponder?

I fly an ultralight aircraft. The GPS is a puck-type device from which the TX line runs to the mode-s transponder. The transponder does not readily show if it is receiving position data. The data is ...
-2
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1answer
202 views

Why don't transponders send gps coordinates and other important info in addition to altitude and transponder code?

I heard that they were waiting for the patent holder's patent to expire, but just wanted to confirm.
4
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2answers
160 views

Should the route be changed if the GPS RAIM prediction fails?

Do i have to change the route if the GPS RAIM prediction has one or more outages along my route?
7
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1answer
315 views

Is a “GPS required” ILS (or other navaid-based) approach considered a “GPS approach” for alternate planning's sake when TSO-C129/196 gear is in use?

If you have TSO-C129/TSO-C196 GPS gear (vs TSO-C145/146 WAAS/SBAS gear), you either have to have a non-GPS approach at your destination, or a non-GPS approach at your alternate. If your choices are ...
1
vote
1answer
366 views

Why do Computer Navigation Fixes still exist now that GPS waypoints can be used to define tracks?

A CNF is a point that defines a navigation track for a GPS, but why is it used when you there are GPS waypoints that are created to define a track?
4
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1answer
489 views

How to leverage Lynx NGT-9000's integrated GPS/WAAS?

I’m inheriting an IFR capable 1964 Cherokee 235 that is not equipped with a GPS. I’m looking at installing a Lynx NGT-9000 to get ADS-B compliant and gain the traffic and weather information. Is ...
4
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3answers
2k views

How does Kalman filtering work in inertial navigation systems?

As far as I understood it correctly most INS-systems use a Kalman filter to compensate measurement errors. I would like to know: Does the Kalman filter compensate the errors from all the onboard ...
4
votes
1answer
756 views

Why does Boeing 737 use 2 Inertial Reference Systems (IRS) and GPS?

According to this website the Boeing 737 aircraft use 2 IRS and 2 GPS: IRS L & IRS R. Why? Apparently they are totally independent of each other. Could somebody explain a little bit why they need ...
5
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1answer
1k views

Why are there GPS MOCAs?

The Pilot Controller Glossary (and other places) define MOCAs as: MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)− The lowest published altitude in effect between radio fixes on VOR airways, off-...
9
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2answers
3k views

Can a pilot use their GPS/FMS to fly a VOR or NDB approach?

GPS is more accurate than a VOR or NDB signal. Can we use a GPS to fly a VOR or NDB approach from the initial approach fix through the missed approach and hold? I know there are two types of ...
1
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1answer
383 views

Is GPS considered to be a navigational facility for the purposes of Ops Spec C055?

For 14 CFR 119 certificate holders, Alternate Airport IFR Weather Minimums are prescribed by Operations Specification (Ops Spec) C055, specifically Table 1 of that specification. Below is a generic ...
3
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1answer
611 views

Are ADS-B Airborne Squitters inherently inaccurate?

Right now I am reading related passages/sections from ICAO Annex 10 Volume 4 and Technical provisions for Mode S Extended squitter. Airborne position squitters are randomly distributed in between 0.4 ...
2
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4answers
1k views

How to convert a pressure height (ADS-B) to a geometric height?

As far as I know, ADS-B broadcast a pressure altitude, so I want convert it to geometric one. How is it possible? e.g in MSG format: http://adsb-decode-guide.readthedocs.io/en/latest/position.html ...
5
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1answer
259 views

Is there any reason to have ADS-B out that is not based on GPS?

The ADS-B system is only as accurate as the location data source it uses. In the US the 2020 ADS-B mandate requires that horizontal location data be from a GPS source with minimum performance ...
4
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2answers
600 views

Do modern aircraft still have mechanical sensors as backup to GPS?

A comment here Why does "no aircraft cross directly over the pole"? indicates that modern aircraft use GPS for navigational purposes, which makes perfect sense. However, do these aircraft ...
-1
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2answers
149 views

Which frame of reference is used to calculate ground velocity? [closed]

During flight, in which frame the ground velocity components are calculated? in the body frame or in the earth frame?
2
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1answer
284 views

Why did my phone's GPS receiver stop working when the plane was descending to land?

Recently I flew on an Airbus A320. I turned my Lenovo A328 Android phone into airplane mode, and then used the default Maps app to watch my position using GPS. Most of the flight it worked normally, ...
4
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1answer
181 views

Why might a moving map Android app consistently record altitude off by 120 feet?

I fly Cessna 172 and Cherokee Warrior both older models without a GPS. I have a very useful freeware navigation app on my android phone which is really good in every regard other than it always reads ...
2
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3answers
313 views

What is the best way to retrieve (and transmit) location (GPS) of plane in real time?

What are some of the best ways to retrieve and transmit the location of a plane I am in, real time. To speak in realistic terms, I'm currently training for my private pilot's license and as such am ...
4
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2answers
370 views

Can I use my non-WAAS GPS receiver with ADS-B in the United States?

I have a older style Garmin 530. Can I use this GPS as the position source for an ADS-B installation?
0
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2answers
673 views

How does GPS measure any plane's ground speed?

How does GPS measure an equipped airplane's ground speed assuming that the plane in question actually uses GPS as opposed to an inertial navigation system or other method? (This was originally part ...
24
votes
13answers
9k views

How did planes measure their speed relative to the ground before GPS?

How did planes measure their ground speed before GPS? If they used some sort of anemometer to measure speed, that would only measure the speed of the plane relative to the air through which it is ...
10
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1answer
429 views

How does an FMS shift after losing all external navaids?

It's not uncommon for polar flights to lose GPS signal (ionosphere issues due to the high latitudes). But it is not a concern because the typical IRS drift is 650 meters for every hour of flight, and ...
12
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5answers
5k views

Which is more accurate for height measurement: GPS or barometer?

I am not a pilot and have come to this site to ask a question about the measurement of height. This is as a result of the comments made as a result of a question in the Physics Stack Exchange forum "...
16
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3answers
19k views

What is the difference between GPS, GNSS and RNAV?

I would like to know the fundamental difference between GPS, GNSS and RNAV. How are they related each other? Are all/some of them synonyms?
5
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2answers
831 views

How can I keep the data on a KLN89b GPS up to date?

I'm looking at a Mooney M20C with a pretty dated panel, but it's airworthy and could be a great opportunity to build some retrac time. The KLN89b GPS is IFR Certified, but is positively ancient. ...
8
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1answer
538 views

Does altimeter setting affect the vertical guidance in a LPV approach?

I had assumed during a WAAS approach when the GPS is in LPV mode, both lateral guidance and vertical guidance are generated from GPS/WAAS signals and the pitot-static system should have no effect on ...
14
votes
2answers
4k views

Can GPS be used in lieu of DME for instrument approaches?

Instrument approach charts list the equipment required to fly them in their name. For this example let's say we have an ILS or LOC/DME 36R approach. This approach requires an ILS receiver for the ILS ...
8
votes
1answer
821 views

LPV/LP approach (RNAV with WAAS): What is actually the “channel number”?

Curious about the answer to this question: How may I verify WAAS channel number on G1000?, I just found that SBAS/WAAS use in aviation seems to be poorly explained. In particular the WAAS "channel ...
2
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0answers
173 views

GPS transmission from Aircraft [closed]

At the risk of being marked as a duplicate question, i am raising my first ever question in aviation. I have always wondered how/why of aircrafts positioning, ever since the "lost" plane of Malaysian ...
1
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1answer
880 views

Where can I download the coordinates of navigation fixes/intersections? [duplicate]

Is there an exportable public database that I may get a copy of all navigational fixes and their corresponding GPS coordinates (latitude, longitude)? p.s. Only US airspace navigation fix information ...
6
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3answers
3k views

What are the differences between a GPS coupled autopilot and a GPSS autopilot?

I'm trying to understand the differences here between an autopilot that is "coupled" into a GPS/NavCom like a Garmin 530W and what GPSS and altitude hold (like in an S-TEC 50 autopilot) have to do ...
7
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1answer
720 views

What US airports have approaches with LAAS?

LAAS (Local Area Augmentation System) is a ground-based GPS augmentation system, intended to be placed at airports to get position accuracy down to around 3m (~10ft) from WAAS's 10m. I've read that ...
-1
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3answers
1k views

Why do planes need line of sight for GPS to work?

Why is the below true when mobile devices such as mobile phones and designer watches with emergency beacons work without Line of sight? Most commercial aircraft transmit their GPS-based position ...