GPS Based Navigation Accuracy Question

[Badmachine]

The Wide Area Augmentation System (WAAS) claims accuuracy of a few meters vertically and laterally. Are airspeed and aerodynamic/atmospheric factors known to alter GPS based navigation accuracy to a large degree?

Thanx.

:ok:

[kijangnim]

Greetings

No, airspeed and/or aerodynamic dont affect the WAAS, LAAS, DGPS, and GPS. :ok:

[411A]

No, airspeed and/or aerodynamic dont affect the WAAS, LAAS, DGPS, and GPS.

Yep, generally the facts.

Now, lets look at one specific GPS navigation unit installation, the King KLN-89B, installed in my private aeroplane.
Enroute navigatiuon accuracy, RNP 5.
Terminal, RNP 1.
Approach accuracy, +/- nine meters, laterally.

Now, this unit is eight years old, new(er) ones do better.
Quite a bit better.

Fact.

The only reason that the Europeans have not embraced GPS is the old familiar tune....'not invented here'.

[Badmachine]

So if an autopilot flight plan intends for a plane to be at a certain location vertically and laterally at a given moment during enroute flight somewhere within WAAS coverage, one can expect that their aircraft will acheive this placement within the stated WAAS accuracy?

Thanx.

:ok:

[reynoldsno1]

atmospheric factors known to alter GPS
ionospheric refraction is the lagest contributing error factor to GPS - and augmentation, such as WAAS etc, exists to help correct this. For aviation use, enhanced integrity is just as important, and augmentation such as WAAS etc, exists to provide this.

[point8six]

411A- that nice Mr. Clinton allowed us to embrace GPS at no cost! What a Gent! Maybe we'll let you embrace our Galileo in turn (don't wait up too long though!), but just maybe they'll find a way of taxing it by then!

[kijangnim]

Greetings
Lets not forget that GPS was created and deployed for and by the US military during the cold war mainly to guide US missiles over Moscow, all paid by tax money, is there any ROI or CBA when military is involved?
Whereas Galileo is a civilian project and unfortunately civilians have bad habits such as ROI and CBA.:}

[NavMonkey]

So if an autopilot flight plan intends for a plane to be at a certain location vertically and laterally at a given moment during enroute flight somewhere within WAAS coverage, one can expect that their aircraft will acheive this placement within the stated WAAS accuracy?

No, that's not a reasonable expectation. The WAAS accuracy relates only to the accuracy of the position solution out of the WAAS box, known as Navigation System Error (NSE). You then have to add the Flight Technical Errors (FTE) which relate to the ability of the aircraft to follow the WAAS guidance. Generally for WAAS, FTE dominates NSE.

[ZEEBEE]

GPS accuracy is based on a number of factors not the least of which is the refraction of the radio propogation through the ionosphere.
Fortunately, the corrections supplied by the various services (WAAS and the like) do a pretty good job of taking out the effects partly because it is assumed that the ionosphere is largely homogenic and what affects the receiver will also be similar at the base stations that provide the reference signals for the correction.
Fortunately, the whole GNS system has had some remarkably quiet ionospheric conditions over the last couple of years to optimise the models and refine the positions of the Ground station network on which the whole thing depends.
When and if the sunspot activity increases again, the disturbance of the ionosphere will degrade the accuracy of the positioning calcs and you may well see some "outliers" that exceed the limits that the equipment specification provides.
Therefore, be aware that the current accuracy that we now enjoy, may not necessarily be provided in the future.

[balsa model]

411A- that nice Mr. Clinton allowed us to embrace GPS at no cost! What a Gent!
- point8six

Actually, it was Mr. Reagan.
Mr. Clinton authorized dropping of the scrambled, extended accuracy portion of the signal. Especially useful if you are in an area that doesn't have access to WAAS and the like.

[TeachMe]

I believe the position error of say 5 meters X/Z and 9 meters Y stated above is a statistical model in which the position is calculated from the various solutions.

One way of looking at it in a stationary unit is like a shooting target. With a stationary shooter and one shot on the target, you can not estimate the centre, with 10 you can make a very rough guess, with a thousand you can be quite close, and with an infinite set of shots you can nail down the location of the centre of the target to the point where Mr Heisenberg gets involved.

Now, with GPS add to this that the satilites are orbiting, and the plane is flying and you get an idea of how difficult things can be and how your accuracy is always limited.

This gets at one reason that GPS units can measure the rise of a volcanic dome in milimeters, get only give it in meters on an airplane.

Now for the original question, GPS works based on the time stamps of the signal, based on an atomic clock on the satilite, sent by the satilite. If that signal for some reason took more or less time to reach the reciever then the accuracy would be altered.

If that was a constant situation then the actual result would be constantly wrong, if it was transient, then the situation would be transient.

As c is different in different mediums, I would not be surprised to learn that results varied based on the atmospheric density, but I would expect that to be in mm over a day and not more. Ionospheric refraction, as noted above, would cause the signal to take a longer route to the reciever and thus result in a differnet solution.

Hope that give some background. And to those who know more, sorry if I am a bit hazy about some parts of it, I sold them about 10 years ago for Garmin, but things have cahnged and I have forgotten much.

[point8six]

My understanding (and memory) is that Ronnie allowed restricted use of GPS to civilians, but Bill signed a Presidential decree allowing full usage to all and sundry (circa 1995?).

[twistedenginestarter]

Do we really need WAAS any more? Surely with SA switched off you're getting enough accuracy to do a precision approach?

[reynoldsno1]

It's the integrity monitoring that's equally, if not more important, than the accuracy for precision approaches.

[balsa model]

point8six:
My understanding (and memory) is that Ronnie allowed restricted use of GPS to civilians, but Bill signed a Presidential decree allowing full usage to all and sundry (circa 1995?).

Timeline as I remember...
ok, ok... it's mostly pasted from Wikipedia:
# In 1978 the first experimental Block-I GPS satellite was launched.
# In 1983, after Soviet interceptor aircraft shot down the civilian airliner KAL 007 that strayed into restricted Soviet airspace due to navigational errors, killing all 269 people on board, U.S. President Ronald Reagan announced that the GPS would be made available for civilian uses once it was completed.
# By 1985, ten more experimental Block-I satellites had been launched to validate the concept.
# On February 14, 1989, the first modern Block-II satellite was launched.
# In 1991 Gulf War 1, soldiers were asking families to send them commercial handheld GPS receivers, since the Army wouldn't/couldn't give them to all who wanted.
# In 1992, the 2nd Space Wing, which originally managed the system, was de-activated and replaced by the 50th Space Wing.
# By December 1993 the GPS achieved initial operational capability.[71]
# By January 17, 1994 a complete constellation of 24 satellites was in orbit.
# Full Operational Capability was declared by NAVSTAR in April 1995.
# In 1996, recognizing the importance of GPS to civilian users as well as military users, U.S. President Bill Clinton issued a policy directive[72] declaring GPS to be a dual-use system and establishing an Interagency GPS Executive Board to manage it as a national asset.
# In 1997, my humble self bought his 1st receiver.
# In 1998, U.S. Vice President Al Gore announced plans to upgrade GPS with two new civilian signals for enhanced user accuracy and reliability, particularly with respect to aviation safety.
# On May 2, 2000 "Selective Availability" was discontinued as a result of the 1996 executive order, allowing users to receive a non-degraded signal globally.

Up until full elimination of scrambling on May 2, 2000, the
instantaneous horizontal plane position error was expected to be less than 100 meters 95% of the time. After that date, we're down to 20 meters. There are very few applications where this raw error cannot be reduced by some form of averaging.

[DC2 slf]

GPS altitude is close to true. ATC at flight levels is based on barometric altimeters set to arbitrary (760 mm 29.92 in) reference pressure. This puts all aircraft on the same basis.

Thus GPS reported altitude should not be used to control FL, in the US or anywhere else.

[john_tullamarine]

There are very few applications where this raw error cannot be reduced by some form of averaging.

Considering that much surveying is now performed with DGPS installations ... with claimed accuracies down to a centimetre or so ... the system's capabilities are not to be sneezed at ...

[411A]

Considering that much surveying is now performed with DGPS installations ... with claimed accuracies down to a centimetre or so ... the system's capabilities are not to be sneezed at ...

Thank you John, and for all the folks who scoff at GPS, and it's accuracy...well, it is very very good, and with my private airplane, is superb, in every respect.
WAAS...or no.
All courtesy of the US taxpayer.

I would say, thanks are appreciated, and you all are welcome.
The USA leading the way...as usual, for precision navigation.
Not forgeting, of course, the Brits, who provided fully automatic landings, so long ago.
And RADAR.
And no, not forgetting the French, with the autoland capabilities on the Caravelle, with Lear-designed autopilots.
The latter lost in history, but 'tis a fact.

[Dale Hardale]

On the subject of GPS indicated true altitude: - for a given indicated flight level, can anyone tell me how this GPS indicated true altitude increases or decreases with change in latitude. :confused:

[gearpins]

Here is how I understand it.GPS sattelites orbit with reference to the center of the earth.that is at a fixed orbital distance.Thus they can pinpoint an a/c position quite accurately in space.But when it comes to the same a/c ht above the earths surface,its only as good as the model of the earth stored in its memory.That happens to be WGS84.Earth not being a perfect sphere does not help either.terestrial gps recievers as used in a car will have a local map of the city stored and position is super imposed on that map.
:)
hence the alttitude discripency.No relevance to change of lat/long

[Statorblade]

I take it that as latitude increases, the WGS84 ellipsoid model will cause a gradual increase in GPS indicated true altitude at a constant flight level, or have I got it the wrong way round ???

[kijangnim]

Greetings

GPS altitude is equal to true altitude +/- geodic correction, you can find some software computing the geodic for a given Lat Long.

[Fitter2]

And you can learn more than you actually want to know about WGS84 here (http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesystemsinfo/guidecontents/guide4.html).

Essentially, GPS altitudes are above a shape which is close to sea level, the errors from real sea level are small. Aircraft normally use pressure altitudes, and the daily variations from Interantional Standard Atmosphere (which a perfect altimeter would indicate) are considerable.

To avoid hitting a lump of cumulo granitus GPS altitude is more useful. To avoid hitting another airborne moving object pressure altitude is what you need.

[A2QFI]

We all know what Mr Clinton emraced and it wasn't always Hilary

[Dont Hang Up]

To avoid hitting a lump of cumulo granitus GPS altitude is more useful. To avoid hitting another airborne moving object pressure altitude is what you need.


Actually GPS height is equally good for terrain avoidance and aircraft separation - assuming everyone is working to a common system. It has in fact been mooted that aviation could, in time, move completely to using geometric height. Not only would this remove the complication of transition altitudes, but could save fuel by avoiding the invisible climbs and descents that are an inevitable consequence of flying through pressure systems. However many aspects of aircraft performance relate to pressure altitude. One could envisage the bizarre situation of aircraft having to request a descent simply as a result of flying into a region of low pressure.

[Fitter2]

Also, the algorithm used for the Z measurement (height) is different from that for X-Y (Lat-Long) because of the geometry of the system, and that it is optimised for land/sea use. The GPS altitude is subject to larger errors, and variation dependant on the satellite constellation being used.

I suspect we are stuck with pressure altitude as the standard for some years to come, in spite of the inherent inaccuracies.

[Keefie]

No,the shape of the earth is known from WGS84, and the height of runway is known relaitive to this datum. Even without augmentation9e.g WAAS) GPS altitude is better than baro

[Keefie]

Iforgot to say that vertical error is not much greater than horizontal, usually a factor around 1.5. It is simply geometry. In vertical , satellites are spread over 90 degrees, horizontal is 360degrees

[kijangnim]

Greetings

Vertical accuracy can be enhanced (for NPA, RNP...) by increasing the lateral accuracy (at that position, I should be at that height on that FPA) and through hybridation of GPS/accelerometers.
GPS is long term very precise, and IRS short term very precise, so we would have to verify if the acceleration measured by the IRS matches the change in position as given by the GPS.
:}

[Keefie]

Ladies and gentlemen, we must not forget the effects of jamming on GPS. Because of the very low signal strength(transmitter is 10k miles away) GPS is dead easy to jam with amateur -made jammers--THIS MEANS SOME FORM OF BACK-UP

[point8six]

Any news on how LORAN-C is shaping as a back-up to GNSS?

[kijangnim]

Greetings

Ladies and gentlemen, we must not forget the effects of jamming on GPS. Because of the very low signal strength(transmitter is 10k miles away) GPS is dead easy to jam with amateur -made jammers--THIS MEANS SOME FORM OF BACK-UP

In fact it is a legacy from the cold war, to achieve the greatest precision the US located most of the GPS ephemeris over Moscow(In fact when we study cases of best GPS reception we call it the "Moscow case") So the Russians being very upset about the gps constellation invented hand held jammers, the story priced these jammers 150 US$ in the streets of Moscow.

[grumpyoldgeek]

In fact it is a legacy from the cold war, to achieve the greatest precision the US located most of the GPS ephemeris over Moscow(In fact when we study cases of best GPS reception we call it the "Moscow case") So the Russians being very upset about the gps constellation invented hand held jammers, the story priced these jammers 150 US$ in the streets of Moscow.

The majority of the ephemeris may or may not be over Moscow, I don't know and I've not seen an authoritative cite that they were.

What I do know is that no US ICBM does or did use GPS for primary guidance. First of all, it is not needed. Inertial guidance with terminal phase radar guidance is extremely accurate. Secondly, as you said, GPS signals can be jammed with a USD 150 device and no ICBM would be risked by such a trivially defeated system.

[Flying Binghi]

Quote -

GPS guided weapons are provided with an integral multi-channel GPS receiver and Inertial Measurement Unit (IMU) which monitors the weapon's locations and attitude to adjust its flight path to accurately impact on the target. In low cost un-powered weapons, the guidance system adjusts the weapon's free fall to hit a pre-selected point fed into the weapon prior to takeoff. GPS is also used in guided missiles and cruise missiles, for mid-course navigation.

Further info from -
GPS/INS Precision Guidance System (http://www.defense-update.com/products/g/gps-guidance.htm)

[dontpickit]

Any news on how LORAN-C is shaping as a back-up to GNSS?

Good news for once! More readable and up to date than the official sites:

International Loran Association (http://www.loran.org/)

[Chart8R]

GPS Altitude
Gearpins is pretty close. GPS uses a spheroidal model of the earth (WGS 84) as a reference which is based on an equipotential surface worldwide. This averages all the peaks and troughs of the real earth's surface in terms of their gravitational effect. The altitude calculated by a GPS receiver will be the distance above this theoretical surface and may disagree with your real altitude above mean sea level. Neither can be equated to the reading on an altimeter (set to QNH) but it is probably close enough for most purposes. Just don't be surprised when you ditch in the Pacific and find your GPS reads -180ft even at high tide.
As far as GPS altitude variation with latitude is concerned, the satellites are not polar orbiting so there may be some reduction of accuracy (increased dilution of precision) in altitude near the poles. That is why you have triple IRS to iron out the wrinkles.
Hope that isn't too much information.
Cheers Chart8R

[L337]

411A: I am a bit bemused by your statement:

The only reason that the Europeans have not embraced GPS is the old familiar tune....'not invented here'.

On every aeroplane that I have flown for the last 10 years or so, and they have been both Airbus and Boeing, they have had GPS installed. I fly for a European airline, and I am European. How have we/ I not embraced it?

It is a wonderful tool, and the greatest single improvement to safety in my 34 year flying career.

[admiral ackbar]

No ICBM's in the USAF inventory use GPS for guidance, too easy to jam as posted above. Some aircraft dropped bombs/missiles use it for guidance though.

The only reason that the Europeans have not embraced GPS is the old familiar tune....'not invented here'.

I am not a tin-foil hat wearing person but I believe the Euros really didn't like the fact that the USA could deny access to the system with the push of a button, one of the reasons for Galileo.

[kijangnim]

Greetings

I think we should stay on the main subject, and avoid unpleasant and useless remarks.:}
GPS was the key enabler for FANS, so whoever invented it doesnot matter, for the good of the entire industry we all have to be able to use it.:ok:

[FairWeatherFlyer]

I am not a tin-foil hat wearing person but I believe the Euros really didn't like the fact that the USA could deny access to the system with the push of a button, one of the reasons for Galileo.

I'm not sure if where you are born affects the conclusion that the system is prone to interference in the EMI sense, perhaps the political control one.

It's an impressive implementation of a simple idea, but if you rely on it as the sole means of navigation and you'll get what you deserve one day! I think the civilian gps is flawed in security terms due to lack of signing of the data, but i welcome corrections on that. I imagine truly malicious practical exploits would be difficult. I've just read there are some simple software based approaches to anti-spoofing - it would be interesting if these criteria are required for aviation.

It is a wonderful tool, and the greatest single improvement to safety in my 34 year flying career.

More so than ACAS/TCAS?

[RAT 5]

2 questions:

1. It is often NOTAM'd the GPS accuracy in NE. Italy is/maybe compromised. Why is this so?

2. Accuracy for NPA's. (nevermind PA's.) I see students fly autopilot LNAV approaches with no regard for checking the raw data lateral navigation. They should, but they don't. Now VNAV approaches are also in use it is also vital to check raw data for vertical. Again not so methodicaly done. They've checked RNP v ANP and all seems hunky dory, so they allow George to lead them to terra firma, hopefully in the correct place.
I heard that in Gulf War 1, (or was ir 2) before Bill, there was a error inputed into the civilian received GPS signal. I don't know how much. If it was deemed necessary - for national security - I presume the USA could do this again. What warning would us civvies be given about this. If the map shift was 0.5nm, and pilots blindly follow George as they do now, Ouch! Would such an inputed error trigger the message "Unable Reqd Nav Perf-RNP" during the initial approach? I assume that any such error would be acceptable at CRZ levels, but only become unsafe during terminal operations. In the CRZ would the ANP be much closer RNP value than normal thus indictaiong that there could be a problem at lower levels? (IRS + VOR/DME cross checking at lower levels would likely be within what non-GPS a/c call map shift parameters. On the B733 that was often > 0.5nm overland and often >1.0mn after seas crossings.)
Given all the NOTAM guff we have to study during the very very short flight planning phase at the start of the day I would hope there would be a very conspicuous method to alert us to any deficiencies in the system.

[411A]

Given all the NOTAM guff we have to study during the very very short flight planning phase at the start of the day I would hope there would be a very conspicuous method to alert us to any deficiencies in the system.

In the USA, anticipated difficulties are clearly indicated in NOTAMS well beforehand.

Perhaps if some European carriers had a reasonable dispatch department in place (Monarch and Lufthansa are especially good in this department, in my experience) all this shuffling through NOTAMS would then be done by the dispatch staff, and called to the attention of the pilots.

You get what you pay for.

[BEagle]

Some slight misunderstandings, I fear?

The US GPS system sends C/A and P code signals. C/A ('coarse acquisition) is the 'civilian' version and used to include Selective Availability (SA) before Clinton ordered it to be switched off. SA applied random time error signals and vehicle ephemeris values to reduce system accuracy to levels which would not pose a serious threat if misused by terrorists.

But with Differential GPS improving C/A accuracy, SA became rather unnecessary. WAAS will improve C/A accuracy even further in the USA and EGNOS will do the same (one of these days :rolleyes:) in €uroland. Most modern Garmin systems include WAAS/EGNOS compatability.

Military systems use far more accurate P-code ('precision') signals which use faster digital code sequences. Originally it was thought that the P-code position information would be 10 x as accurate as C/A; however, C/A was so accurate that SA was needed to degrade it when necessary.

It would be possible for a civilian user to use some clever processing to use P-code signals by detecting the C/A 'handover word', accessing the L1 and L2 frequencies and using the P-codes. So the P-code is also encrypyted; it is then know as Y-code. Unless cryptovariables are loaded into a mil spec GPS receiver, it will only use C/A positioning.

[galaxy flyer]

Some more info:

KGPS is the "location" needed to find GPS NOTAMS. Or go to the US Coast Guard site, which for some reason, is the source of those NANU (GPS for NOTAM) Notice Announcements for Navstar Users.

The US Mil cannot use Y-code for navigation in civil airspace, our GPS navigation was certified for C/A signals only. There have been one or two huge screw-ups (read: domestic GNEs using bombing computers as nav devices in US civil airspace :=)

When they started bombing with GPS navigation, errors were found by targeteers where bombs aimed for the top of the building (think elevator shaft) instead hit near the first floor. Hence targeting had to get smart on how to program for elevation. Also, a mid-90s Space Shuttle mission, I believe classified, spent 12 days mapping the earth for elevations which, in turn, produced the obstacle and terrain data used by Enhanced GPWS.

The detritus of the years

GF

[Chart8R]

The problems with GPS in Italy used to be interference from television signals. I thought that had been sorted out now but I will watch the Notams.

The RNP value associated with a nav fit has an accuracy, integrity, continuity and availabilityrequirement. The GPS element of that nav fit has a receiver with additional channels which are used for monitoring the integrity of the signals. This is known as GPS Receiver Autonomous Integrity Monitoring (RAIM). Any jamming or selective availability imposed on the GPS would be detected as an increase in the dilution of precision (the cocked hat gets bigger) and a RAIM failure. ICAO specifications for RNP receivers require pilot alerting of inadequate navigation performance whenever actual performance is worse than RNP.
A good review of FMS integrated navigation can be found at http://adsb.tc.faa.gov/WG4_Meetings/ASAS10%202005-July/STP%20appendix%20B_08-05-2005%20AWW.pdf (http://adsb.tc.faa.gov/WG4_Meetings/ASAS10%202005-July/STP%20appendix%20B_08-05-2005%20AWW.pdf)
Cheers Chart8R

[411A]

Or go to the US Coast Guard site, which for some reason....

That is because....
The USCG maintains the very first navigation equipment (transmitters) used for area navigation...LORAN.
Loran C now...Loran A, many years ago.
Very accurate, if used properly....and with Loran A, it took a definite technique, ofter mastered only by the professional Navigator.

[RobinR200]

Accuracy is only one performance item to be respected by a navigation system. I write NAVIGATION system. GPS is by all means just a POSITIONING system. Only thru software programs using databases one can make a Navigation system out of the GPS. However, the other three factors are availabitliy, reliability and integrity. On the last parameter, i.e. integrity, GPS fails in more than one respect to be a precision system. (think of these databases being filled by humans!).

Nevertheless, for en-route purposes it´s a hell of a system. I love it too. Especially in my CAR!!

But to be a true precision NAV sytem, one has to consider definitely other system like MLS. But off course...as the yanks didn´t invent it, they don´t adopt it.

[kijangnim]

Greetings'

quote:
However, the other three factors are availabitliy, reliability:confused: and integrity. On the last parameter, i.e. integrity, GPS fails in more than one respect to be a precision system.

Availability, Continuity, and Integrity are criteria that if demonstrated at 95% of the time will grant a sole mean of navigation certification status to the system.
Now as integrity is a stake for the GPS, then it cannot be certified as sole mean but as PRIMARY mean of navigation, PRECISION has nothing to do with this :}
Furthermore as per TSO129C a self embarked software, within the receiver, has to have the capabitility to verify the integrity, in our case it is called RAIM, Receiver Autonomous Integrity Monitoring :ok:

[Denti]

Dunno, we fly GBAS approaches in Europe to CAT I limit with the availability of CAT III once certified. It is very precise indeed, no difference to ILS from a users standpoint. However that is ground augmented so of course you can get more precise position data than with pure GPS.

Sadly, those approaches are still flagged as being in a trial phase, however they work wonderfully so far and we had no glitches whatsoever.

[RAT 5]

Please: Has anyone got an answer to the questions asked? Pilots should not play like politicians and answer the question they thought was asked.

[kijangnim]

Greetings,
what was the question :confused:

On the Airbus there is a page called PREDICTIVE GPS, it will show RAIM availabilty at a specific waypoint (destination for example) at a specific time (ETA)
On B777 the GPS receiver will compute a data relevant to RAIM availability and sends it to AIMS.

So I guess that if you are on Boeing world on top of the NOTAMS specific to GPS you need to have RAIM holes.

Because you cannot shoot an approach using GPS as main sensors if RAIM is not available.

RAIM needs 5 sats (if you are baro aided) 7.5 deg above the horizon.
Now North of Italy is mountaineous? may be mountain shaddowing is reducing the number of sat you can receive.

[kijangnim]

Greetings
What was the question :confused:
RAW DATA MONITORING was mandatory at time aircraft were equipped with a single FMS, to enable the crew to continue the approach on Raw Data in case of FMS failure
if you are equipped with dual FMS with GPS, then you dont need to cross check the raw data as long as ANP<RNP.
But before all this the Approaches MUST BE VALIDATED, and the validation depends on the type on NPA you want to fly, is it Classic NPA overlay, is it RNAV, is it RNP, is it GPS. :E

[411A]

Now as integrity is a stake for the GPS, then it cannot be certified as sole mean but as PRIMARY mean of navigation.


Quite incorrect, for ops in the USA or for US registered aircraft, worldwide.
WAAS certified GPS navigators can (and are being) installed in aircraft as a sole means of navigation, and are fully certified as such.

Don't need VOR.
Don't need ADF.
Don't need DME/TACAN.

WAAS/GPS only, if you so desire.

Of course, others trail behind, which is no surprise...:rolleyes:

[kijangnim]

Greetings

GPS (excluding waas laas dgps) is primary means of navigation, my statement was on GPS only :)

[411A]

GPS (excluding waas laas dgps) is primary means of navigation, my statement was on GPS only

In that case, then yes, you are correct.
However, lets look at the enroute case.

L1011 aircraft equipped with dual Honeywell HT-9100 or Universal UNS-1M GPS navigators.
Fully approved for MNPS north Atlantic ops as a sole means of enroute navigation...and this was over ten years ago.
I suspect that other aircraft/equipment combinations were as well.
Dual Omega equipped aircraft, is another example.
Now, having said this, usually these aircraft were also equipped with INS units, but not always...and not specifically required by the ops specs issued to the specific carrier.

Now, a few will say...never.
Oddly enough, there usually are exceptions, fully approved by the relevant regulatory authorities.

[kijangnim]

Greetings

as far as I know, the IRS, (Omega before it was decommissioned) is the only Sole mean of navigation, even for enroute consideration GPS still primary means, LITTON recently attempted to certify the AIME solution (Autonumous Integrity Monitoring Extrapolation) using Kalman filtering, but I am not sure if they did get it.
We have to remember that the Integrity is the GPS weak point, and therefore it cannot be certified sole mean, the last attempt I know of was the Rio de Janiero ICAO meeting in 1998, integrity and jamming closed the subject.

[411A]

We have to remember that the Integrity is the GPS weak point, and therefore it cannot be certified sole mean....

Nevertheless, it has been in the past...ten years ago to be specific, for some installations, for enroute guideance.

I suspect our UK/European friends just simply don't like the GPS idea, due to the 'not invented here' syndrome.
And yet...they will use one to find the nearest Italian restaurant in a strange town where they have never been before...:}

Go figure.:rolleyes:

[RobinR200]

continuity of sevice equals reliability but only on a short term:ok:

[kijangnim]

Greetings 411A

Personally i am not European, and living in France doesnot make you French either, so I dont have any bias about who made what :}.
I want to point out that during the Rio de Janiero ICAO conference the Sole mean of navigation GPS certificate was dropped because of JAMMING, it was never dropped because of other integrity issues since RAIM handles it very nicely :ok:

[Genghis the Engineer]

Fact.

The only reason that the Europeans have not embraced GPS is the old familiar tune....'not invented here'.

There's an element of that but also the awareness that:

- Somebody we have no control over can turn it off.
- It's only one system, and fallible like any human endeavour
- It is very easy to jam.

But, GPS approaches are coming in Europe and the UK, they're approved now in the UK for some GA, - and once Galileo is fully available, a combined GPS/Galileo receiver will solve at least two of those three problems, and make the third harder to do.

G

[Badmachine]

Is there reference material available that can predict how much Flight Technical Errors can affect aircraft positional accuracy while in GPS based navigational flight?

[kijangnim]

Greetings,

No material describing such prediction (FTE), GPS or DME/DME or ILS sensors dont matter, what matters is that ANP(Boeing) EPU (Airbus) is smaller than RNP for that particular area.
In fact today the aircraft position doesnot matter at all, the hole concept is based on a sphere containing the aicraft, the aircraft position within the sphere dont matter, however the diameter of the sphere MUST always be smaller than the RNP, that can be visualized as a tube
:ok:

[Badmachine]

For example, if a WAAS-based autopilot flight plan intends for an aircraft to be at a particular place at a particular time, to what degree will FTEs affect the ability of such an aircraft to acheive the intended placement?

Does WAAS govern aircraft accuracy regarding runway approaches or does this fall within LAAS coverage?

Thanx.

:ok:

[Keefie]

Yes, FAA made measurements on their 737.Roughly the azimuth error is directly proportional to distance from localiser. I am presently in UK and return to US next week, where the data is , .if you e-mail me I will send it to you by e-mail My e-mail is [email protected]

[Keefie]

You need WAAS for integrity if you are going to do low minma