Accuracy of GPS in Garmin 430/530

you do it, you built it and get rich.
"Will" wrote in message
...
| As the lawyers like to say in court "evidence not in the
record." There
| is no proof at all for the claim that some straightforward
math calculations
| in any GPS software is going to to double the cost of the
GPS. What I was
| describing doesn't require any new hardware, and it's just
a matter of
| calculating some accuracy numbers and representing them in
the standard UI.
|
| If it prevents one death that results in a multi-million
dollar lawsuit, it
| would payback the one man-month of work it might take to
do those
| calculations in software 100 fold or more.
|
| --
| Will
|
|
| "Jim Macklin" wrote
in message
| news:4bx3g.8797$ZW3.1447@dukeread04...
| And it could double the cost of the system for no useful
| purpose.
|
| I'm sure that if anybody wanted a custom made GPS unit,
| Garmin or some other company would be happy to take your
| million dollars and build you one or even two of them.
|
| --
| James H. Macklin
| ATP,CFI,A&P
|
|

There
is no proof at all for the claim that some straightforward math calculations
in any GPS software is going to to double the cost of the GPS.

Have you ever written software?

If it prevents one death that results in a multi-million dollar lawsuit, it
would payback the one man-month of work it might take to do those
calculations in software 100 fold or more.

It is actually more likely to =cause= a death - to a pilot who decides
to rely on a handheld because it has RAIM.

Jose
--
The price of freedom is... well... freedom.
for Email, make the obvious change in the address.

In article ,
Jose wrote:

It is actually more likely to =cause= a death - to a pilot who decides
to rely on a handheld because it has RAIM.

Jose

And tell me that pilots aren't already using those "for situational
awareness only" extended runway centerlines drawn on the moving maps of
VFR-only handhelds to cobble up their own instrument approaches?

And tell me that pilots aren't already using those "for situational
awareness only" extended runway centerlines drawn on the moving maps of
VFR-only handhelds to cobble up their own instrument approaches?

.... and tell me that one day some widow is going to sue, and the chance
of her winning is on the heads or tails of a token.

Now, without RAIM the defense "it was VFR only, that was an SPT" holds
more water. With RAIM, the offense is "you built it to appeal to
instrument pilots..." We already have culpability in "appealing to
children", this is not much of a stretch.

And the truth is, RAIM is not useful VFR. It adds complexity to the
software and the screen, to no navigational benefit. But it is
essential IFR (or IMC anyway). So the argument above will gain
traction. Food for lawyers. We pay for it.

Jose
--
The price of freedom is... well... freedom.
for Email, make the obvious change in the address.

"Dave S" wrote in message
ink.net...
How would the use of the GPS be responsible for someone's death?

Cessna lost a famous case that steered it out of general aviation for a few
years and got a one billion dollar judgement because a pilot hit a fence.
How was it Cessna's fault that the pilot hit the fence? Heck if I can
figure that out, but if a case can be made a lawyer would go for the money.


Now you try to justify its cost/benefit by a hypothetical lawsuit over
the lack of something that is not mandated, not needed and not justified?

Hold on, and stop changing topics and talking about new issues. There was
never any debate about FAA mandate. The discussion about whether it is
needed or justified is a separate discussion within the thread. Jim made a
comment that the feature I described would double the cost. I was trying
to respond just to that point. I did so by pointing out:

- It won't take more than a man month to simply code the needed algorithms
(and I doubt it would take that).

- There wasn't any proof for the claim in any case.

- To the extent it might control some kinds of liability it might actually
be cost beneficial rather than just incurring some additional labor cost.

--
Will

"Jose" wrote in message
om...
There
is no proof at all for the claim that some straightforward math
calculations
in any GPS software is going to to double the cost of the GPS.

Have you ever written software?

I have managed at least three teams commercially on four projects in the
last 10 years, and at least two of those projects had over 200K lines of
code. So I guess that would be a yes.


If it prevents one death that results in a multi-million dollar lawsuit,
it
would payback the one man-month of work it might take to do those
calculations in software 100 fold or more.

It is actually more likely to =cause= a death - to a pilot who decides
to rely on a handheld because it has RAIM.

First, the pilot shouldn't be using the handheld in IMC unless he got there
during an unplanned emergency and primary instruments failed. Your
position appears to be that any non-FAA certified tool should be
deliberately crippled in order to make sure that pilots don't cheat and try
to use the instrument during IFR flight or during an emergency flight into
IMC? By that logic, we should just stop all technological development,
because God forbid that someone innovates and makes something that is
actually precise, useful, and more advanced than what is already in the
cockpit?

Once the pilot is in an emergency condition, how do you figure that the
pilot is better off following a GPS trace in complete ignorance of the fact
that it is inaccurate by thousands of feet? Since when is (optional)
knowledge a bad thing?

In any case, if someone deliberately takes an uncertified instrument and
uses it as a primary instrument in IFR, they are violating the rules and I
guess they are responsible for their own bad behavior.

--
Will

I have managed at least three teams commercially on four projects in the
last 10 years, and at least two of those projects had over 200K lines of
code. So I guess that would be a yes.

Bug free?

First, the pilot shouldn't be using the handheld in IMC unless...

True. But pilots will do things they shouldn't do, and the equipment
maker gets sued, whether they helped cause the crash or not. This is
expensive even if they win.

Your position appears to be

It's not my position. I am proposing reasons why it isn't done.
Whether is =should= be done is another question, but I can easily see
why they don't do it.

By that logic, we should just stop all technological development,
because God forbid that someone innovates and makes something that is
actually precise, useful, and more advanced than what is already in the
cockpit?

This is the logic behind a lot of aircraft design. I am not a lawyer,
but I vaguely recall a case against (I think) Cessna which came down to
"this design is bad and caused the crash. You knew it was bad because
twenty years later you improved it". I don't know if Cessna won or
lost, but the idea had traction.

In any case, if someone deliberately takes an uncertified instrument and
uses it as a primary instrument in IFR, they are violating the rules and I
guess they are responsible for their own bad behavior.

Well, the pilot does an SPT and kills somebody on the ground, who sues
the pilot, the plane maker, the GPS maker, the airport where the plane
took off from, and the stars in the sky. It comes down to who has more
money from which to collect. If the pilot and his insurance is
significantly less than the GPS maker and his insurance, then any sane
lawyer will go after the GPS maker. The argument that the GPS maker
enticed the pilot to use this device in IMC will likely gain traction
against a judge and/or jury of non-pilots who see many other cases of
enticement for profit.

It =is= the pilot's fault. But the victim is dead and the GPS maker has
more money. I wouldn't blame the GPS maker for being gun-shy about
putting in a feature of less than dubious value in the face of this.

I wish it were different.

Jose
--
The price of freedom is... well... freedom.
for Email, make the obvious change in the address.

Will wrote:


Hold on, and stop changing topics and talking about new issues. There was
never any debate about FAA mandate. The discussion about whether it is
needed or justified is a separate discussion within the thread. Jim made a
comment that the feature I described would double the cost. I was trying
to respond just to that point. I did so by pointing out:

- It won't take more than a man month to simply code the needed algorithms
(and I doubt it would take that).

If you have an avionics engineering background, you should know that
TSO-C129 is not only enabling, it is specific and fairly limiting. The
avionics vendors are constrained by the TSO. The TSO serves a purpose,
to permit an IFR platfrom for GPS terminal and approach operations
within a National Airspace System that has yet to be declared
GPS-primary, much less sole source.

I am very familiar with the Garmin 530. I have also owned three Garmin
aviation handheld units, the 195, 295, and 296. The handhelds have had
progressively sophisticated features that the Garmin 530 does not have
because the 530 had to go through a very extensive certification process
to be qualified for IFR operations. Not so with the handhelds.

Garmin has millions tied up in both their IFR and VFR programs. They
seem to be progressing along quite nicely in providing products
appropriate for the operation.

I have my own ways of independendly verifying the accuracy of my 296 by
using DME at the appropriate time. That provides a great accuracy
check, which is valid for a limited period of time. But, it is hardly
approach RAIM. Also, the TSO-C129 sets actually increase accuracy as
well as assure a high level of integrity in the final approach segment
using approach RAIM.

As I said previously, and you chose to ignore, you seem to be looking
for a full press RNP platform, which would not only have redundant
alerting and actual navigation performance (ANP) it is not limited to
the three levels of sensitivity that TSO C129 constrains; en route,
terminal, and approach. (BTW your handheld does not meet those
sensitivity requirements, either).

A Boeing 727-NG, which is available is a business jet version, has
everything you are looking for, including three IRUs that are constantly
updated by GPS and have position blending. Then, in the event of a
failue of GPS (typically local jamming) the IRUs will continue to
provide very low numbers of RNP accuracy, integrity, and continuity.

I think you might be in over your head a tad and, in the process,
digging a hole for yourself for no good reason. ;-)

Roy Smith wrote:

In article ,
Jose wrote:


It is actually more likely to =cause= a death - to a pilot who decides
to rely on a handheld because it has RAIM.

Jose


And tell me that pilots aren't already using those "for situational
awareness only" extended runway centerlines drawn on the moving maps of
VFR-only handhelds to cobble up their own instrument approaches?

You can't design the system to account for cheaters.

Will wrote:


Once the pilot is in an emergency condition, how do you figure that the
pilot is better off following a GPS trace in complete ignorance of the fact
that it is inaccurate by thousands of feet? Since when is (optional)
knowledge a bad thing?

With a properly mounted attenna and a check of satellite geometry, that
simply is not going to happen with a good handheld, such as the Garmin
296/396.

I have hundreds of hours using the 195/295/296 in aviation, automotive,
and marine modes and have never, ever seen significant degragation of
accuracy when the antenna has a good view of the sky.

I have seen very poor solutions, however, when using it through a cabin
window of an airliner. I have also seen very good accuracy in that
circumstance, depending upon available satellite geometry.

Finally, as I said before, an accuracy check with DME in a light
aircraft can provide a great, short term, accuracy and integrity check
for a handheld, albeit now as good as approach RAIM.

Also, the later Garmin 500 series as fault detection exclusion, which
makes them certified for sole-source oceanic IFR. Were you aware of that?