Violating Airspace with GPS

It appears that a lot of pilots are violating airspace even with GPS on
board.

I would like to hear some feedback as to how pilots are violating airspace
with GPS. I address this in my online book, www.cockpitgps.com. I have my
hypothesis, but I would like to hear your experience or scenarios that you
have heard involving this issue.

Also of interest is how you might be using GPS to successfully avoid
airspace violations.

Other hypothesis are also welcome.

Thanks,

John Bell
www.cockpitgps.com

Here is my hypothesis:

I have already mentioned in my discussion of database currency that you
should set up a routing around any airspace and check it with a current
chart before flight. Even with a current database, it is possible for the
GPS to get you into trouble with airspaces.
Aviation receivers can be setup to display airspace boundaries and to give
warnings before entering certain airspace classifications such as category B
airspace. These warnings can be a great benefit or a nuisance depending on
the type of flying that you are doing. Thus, most receivers allow you to
turn them on or off. Additionally, which boundaries will display and at what
point of zooming out they will disappear can be set. The ability to make
these settings is a good feature and I would not want to see this changed.
However, it is possible to have the GPS not display or not warn of an
impending airspace violation if you have the GPS set up incorrectly for the
mission.
Even if the airspace boundary is displayed, it is often difficult to decide
what boundary a given line applies to. On the Garmin aviation receivers it
is possible to cursor over the point to get a description. On a handheld GPS
just press the rocker pad up, down, left, or right to start moving the
cursor. On the GPS 400 and 500 series, press in on the knob and then start
moving the cursor. Move the cursor to highlight the line and press the ENTER
button to get information on the airspace. This is a great feature at the
planning stage and is occasionally useful in flight. When you have
preplanned the route and have a route line, the context of the border is
obvious. However, I think that it is possible to confuse borders and violate
airspace without first creating a route using a chart before flight.

"John Bell" wrote in message om...

Other hypothesis are also welcome.

Class B airspace, not category B.

Your simplified definition of GPS, while one of the common ones often espoused
has no basis in reality. This is not how GPS works.

Your information on RAIM is wrong. What is unique about the RAIM used in IFR
approved GPS's is not that it determines when the satellite geometry is giving you
an error NOW, but computes if it will fail while during the expected duration of flying
an instrument approach.

I will see where I wrote category B instead of class B. It is simply a
typo. Thanks for catching that.

I am certainly up for a better explanation of how GPS works. Indeed my
information comes from the common espousals.

I understand the concept of RAIM prediction, that the GPS can predict the
unavailability of RAIM. However, I was not aware that RAIM had the ability
to predict as oppose to detect positioning errors.

I would appreciate further information on either basic GPS or RAIM.

John Bell


"Ron Natalie" wrote in message
m...

"John Bell" wrote in message
om...

Other hypothesis are also welcome.

Class B airspace, not category B.

Your simplified definition of GPS, while one of the common ones often
espoused
has no basis in reality. This is not how GPS works.

Your information on RAIM is wrong. What is unique about the RAIM used in
IFR
approved GPS's is not that it determines when the satellite geometry is
giving you
an error NOW, but computes if it will fail while during the expected
duration of flying
an instrument approach.

On Thu, 30 Oct 2003 20:38:40 GMT, "John Bell"
wrote in Message-Id:
:

I am certainly up for a better explanation of how GPS works.

Are you aware of this mailing list?

GPS for Aviation:

http://www.lsoft.com/scripts/wl.exe?...ISTSERV.UNB.CA

There are very knowledgable folks willing to answer all your questions
there.

Larry Dighera wrote

There are very knowledgable folks willing to answer all your
questions there.

:-) :-) Since John has written texts on GPS Navigation, I suspect
that he was pulling someone's leg.

http://www.smallboatgps.com/ http://www.cockpitgps.com/


Hi John, how's things going? Remember meeting at SnF?

Bob Moore

Robert,

I do indeed remember meeting you in Lakeland. Whenever I see one of your
posts, it is like picking up a paper and seeing a byline from a reporter
that I respect.

Actually, my response to Ron Natalie was a little more than tongue in cheek.
It was somewhat of a combination of defensiveness and worry that I might be
spreading bad information. Ron's statement that my explanation of how GPS
works: "while one of the common ones often espoused
has no basis in reality. This is not how GPS works" has me curious.

Unfortunately, Ron's statement unfortunately gives me little to correct my
understanding if it is indeed wrong. Luckily, even if my explanation of how
GPS works is totally incorrect, it should not have serious consequences as
far as usage is concerned.


John

"Robert Moore" wrote in message
. 7...
Larry Dighera wrote

There are very knowledgable folks willing to answer all your
questions there.

:-) :-) Since John has written texts on GPS Navigation, I suspect
that he was pulling someone's leg.

http://www.smallboatgps.com/ http://www.cockpitgps.com/


Hi John, how's things going? Remember meeting at SnF?

Bob Moore

In article , Ron Natalie wrote:

Your information on RAIM is wrong. What is unique about the RAIM used in IFR
approved GPS's is not that it determines when the satellite geometry is giving you
an error NOW, but computes if it will fail while during the expected duration of flying
an instrument approach.

That's RAIM *prediction*. RAIM is very capable of failing during an approach if
you don't check the prediction ahead of time, at least on our Garmin 430.

I don't know what John's information on RAIM is, since it will be two or three
hours before his books is downloaded.

Regards,

Mike

"Mike Beede" wrote in message ...
In article , Ron Natalie wrote:

Your information on RAIM is wrong. What is unique about the RAIM used in IFR
approved GPS's is not that it determines when the satellite geometry is giving you
an error NOW, but computes if it will fail while during the expected duration of flying
an instrument approach.

That's RAIM *prediction*. RAIM is very capable of failing during an approach if
you don't check the prediction ahead of time, at least on our Garmin 430.

Yes...and if you read his document, he doesn't distinguish between RAIM (which many
non-IFR units do just fine) and predictive rain.

That's RAIM *prediction*. RAIM is very capable of failing during an
approach if
you don't check the prediction ahead of time, at least on our Garmin
430.

Yes...and if you read his document, he doesn't distinguish between RAIM
(which many
non-IFR units do just fine) and predictive rain.

Ron,

I am open to argument and corrections of any misunderstandings that I might
have. It was my impression that RAIM is strictly a integrity monitoring
scheme rather than a predictive function. RAIM uses redundant satellite
signals as a cross check to monitor whether any satellite signals are bad.

Since a GPS knows the satellite orbits from the almanac, a program can be
designed to predict if satellite positioning will be adequate to support
RAIM at a given time and place. Receivers such as the Garmin 430 have this
RAIM prediction feature. Knowing the satellite orbit information, it is
also possible to predict and issue a notam for areas and times when RAIM
will be unavailable.

Using the same techniques for predicting RAIM coverage, it would be possible
to warn of impending satellite geometry and coverage problems. I do not
know whether or not any GPS receivers do this automatically beyond the RAIM
prediction program such as in the AUX menu of the Garmins.

I guess I understand RAIM as a monitoring the integrity of the satellite
signal rather than a predictive function. However, I will agree that there
are ways to predict whether or not RAIM will be available.

I am open to corrections if you will explain your reasoning and possibly
site sources.

Thanks,

John Bell

"John Bell" wrote in message ...
That's RAIM *prediction*. RAIM is very capable of failing during an
\
I am open to corrections if you will explain your reasoning and possibly
site sources.

I believe you understand it, now go back and read your book. It is NOT the
presence of RAIM that distinguishes the IFR GPS's (many non-IFR GPS's
also have it), it's the predictive feature that is required/distinguishing.