GPS altitude again is close to actual

"Roger (K8RI)" wrote:
WAAS isn't part of GPS.

That comment may be helpful in a GPS newsgroup where the technology is
discussed in the absence of any application, however, in an aviation
newsgroup, discussions of GPS are primarily about the application, and in
that context WAAS is inseparable from GPS; in other words, in aviation
there is no application for WAAS independent GPS AFAIK. So, your above
claim is extremely off-topic, at best.

Neil

Actually he is correct. WAAS is not part of GPS. You don't need WAAS
to use GPS for aviation.

True but my GPS says WAAS enabled.


Ron Lee

Do you know of an aviation use of WAAS that isn't tied to GPS? That is the
issue.

I've never heard of any.
As we use it you can use GPS withoug WAAS , but not WAAS without GPS.
IOW it's an augmentation system.

Exactly, it is an augmentation system developed for and funded by the
FAA. The notion that WAAS is part of GPS is like saying that NDGPS or
CORS or any other separate systems that use or work with GPS are GPS
systems.

Of course WAAS cannot be used without GPS since it corrects GPS
signals and provides an integrity function. WAAS is worthless without
GPS but the converse is not the case.

Ron Lee

Ron Lee writes:

Exactly, it is an augmentation system developed for and funded by the
FAA. The notion that WAAS is part of GPS is like saying that NDGPS or
CORS or any other separate systems that use or work with GPS are GPS
systems.

None of the augmentation systems are part of GPS.

It worries me that I see a lot of ignorance of GPS in the aviation
community. It is not surprising given the newness of the technology,
but it is worrisome because people often rush to embrace a new
technology because of the gee-whiz factor, long before they understand
the technology and its limitations. It's like people who drive off a
pier into a river because they don't realize that GPS can be
dramatically incorrect in urban environments.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Recently, Mxsmanic posted:

Ron Lee writes:

Exactly, it is an augmentation system developed for and funded by the
FAA. The notion that WAAS is part of GPS is like saying that NDGPS
or CORS or any other separate systems that use or work with GPS are
GPS systems.

None of the augmentation systems are part of GPS.

And, as usual, your learn-resistance has forced you to post yet another
useless and off-topic repsonse.

It worries me that I see a lot of ignorance of GPS in the aviation
community.

You are mistaking the responses as ignorance because you are refusing to
understand that in aviation, only the application matters to the pilot. We
are trained to use and understand the issues involved in every piece of
equipment in the airplane. That means that we understand the limitations
of non-WAAS-enabled GPS, for example, and why we can't use them for IFR
approach; it is *exactly* because WAAS provides accurate alititude
information. If you disagree, take it up with the FAA, where you will be
told exactly the same things that many of us have told you. Furthermore,
we understand such not-so-subtle differences as whether something is
_measuring_ angles or the timing of signals, and won't fall victim to such
misconceptions. The only reason that you won't fall victim to your lack of
knowledge is that you aren't doing anything real.

Neil

There was a story a while back (don't know if it's true or not, but sounded
legit) that some guy was demonstrating his latest, greatest GPS by using it
to taxi into his hangar. It wasn't quite that accurate and the repair bill
wasn't cheap.

mike

"Mxsmanic" wrote in message
...

It worries me that I see a lot of ignorance of GPS in the aviation
community. It is not surprising given the newness of the technology,
but it is worrisome because people often rush to embrace a new
technology because of the gee-whiz factor, long before they understand
the technology and its limitations. It's like people who drive off a
pier into a river because they don't realize that GPS can be
dramatically incorrect in urban environments.

--
Transpose mxsmanic and gmail to reach me by e-mail.

mike regish writes:

There was a story a while back (don't know if it's true or not, but sounded
legit) that some guy was demonstrating his latest, greatest GPS by using it
to taxi into his hangar. It wasn't quite that accurate and the repair bill
wasn't cheap.

One problem with GPS is that accuracy can be rapidly and significantly
degraded by the presence of buildings or mountains or other obstacles
that reflect or block signals. This is why GPS isn't likely to be
very accurate in the streets of Manhattan. The system itself provides
good accuracy, but in order to obtain that accuracy, you have to be
able to receive the signals without interference. On the ocean, in
the countryside, or in the open sky, you can receive signals very well
indeed, but once you are on the ground, the situation changes.

Another problem, not actually part of GPS per se, is moving maps.
Your GPS position may be accurate, but that doesn't guarantee that the
map is accurate. If the mountain on the map is in the wrong place in
relation to its real-world position, having high accuracy from GPS
won't help you. Very often map errors are more of a problem than
errors in the GPS itself.

Note that WAAS and LAAS will _not_ compensate for either of the above
types of error. Differential GPS systems like this work best when you
are at exactly the spot used as a reference for the corrections. If
you are anywhere else, the corrections may not be right for your
position. The further away you are from the surveyed reference
position used to generate the corrections, the more likely it is that
your position will be incorrect.

Some of these systems also correct for atmospheric and other effects,
but here again, the corrections are most useful when you are in the
exact position for which they are generated. If the reference point
is in Cheyenne and you are in Denver, the corrections may be well off
the mark.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Mxsmanic wrote:
[...]
Note that WAAS and LAAS will _not_ compensate for either of the above
types of error. Differential GPS systems like this work best when you
are at exactly the spot used as a reference for the corrections. If
you are anywhere else, the corrections may not be right for your
position. The further away you are from the surveyed reference
position used to generate the corrections, the more likely it is that
your position will be incorrect.

While correct for the case of LAAS and DGPS, this is not correct in the
case of WAAS.

Hint: W != L

Regards,
Jon

writes:

While correct for the case of LAAS and DGPS, this is not correct in the
case of WAAS.

It's true for WAAS, too. WAAS has only a few fixed reference points
and extrapolates for all other points.

--
Transpose mxsmanic and gmail to reach me by e-mail.

Mxsmanic wrote:
writes:

While correct for the case of LAAS and DGPS, this is not correct in the
case of WAAS.

It's true for WAAS, too. WAAS has only a few fixed reference points
and extrapolates for all other points

You don't understand how WAAS works.

You stated:

" The further away you are from the surveyed reference
position used to generate the corrections, the more likely it is that
your position will be incorrect."

This is false. Being inside the reference network is all that matters,
proxitimity to a WRS does not matter.

Regards,
Jon

Mxsmanic wrote:


Another problem, not actually part of GPS per se, is moving maps.
Your GPS position may be accurate, but that doesn't guarantee that the
map is accurate. If the mountain on the map is in the wrong place in
relation to its real-world position, having high accuracy from GPS
won't help you. Very often map errors are more of a problem than
errors in the GPS itself.


Once again you don't know what you're talking about. Even if the map
were out of spec a little it doesn't matter as you aren't flying that
close to the mountains if you are IFR. An actual pilot would know that.




Note that WAAS and LAAS will _not_ compensate for either of the above
types of error.

Doesn't matter.





Differential GPS systems like this work best when you
are at exactly the spot used as a reference for the corrections. If
you are anywhere else, the corrections may not be right for your
position. The further away you are from the surveyed reference
position used to generate the corrections, the more likely it is that
your position will be incorrect.

Completely irrelavant for aviation.