Re: Subscription to NASD CD-ROM (was: embedded ...)

[Bob_Deep <bobd@cssgroup.com>]

Brian Lloyd wrote:
> 
> On Fri, 11 Feb 2000, Bob_Deep wrote:
> 
> > Andy Ross wrote:
> >
> > I thought that the Jeppeson approach plates, though different looking
> > than the NOS ones, where functionally equivalent.
> 
> They are.  I use both interchangeably.
> 
> > If memory serves,
> > they added a bit more information to their approach plates, but nothing
> > you could not figure out from the NOS charts you should have in the
> > plane anyway.
> 
> That is correct.
> 
> > I also believe that it's the FAA that approves ALL instrument
> > approaches, going so far as to actually fly them in a specially equipped
> > aircraft to verify that everything works together right.  Does Jeppeson
> > verify approaches?  Do they go out and spend the money to fly them?  No
> > they don't.
> 
> Verification of the approach is independent of generating the charts.
> You seem to be arguing that the NOS plates/charts are better than
> Jeppesen.  I don't think you can support that statement.

Oh no.. I'm saying that the NOS stuff is the legal minimum to which
Jeppeson adds.

> > They got their start by making approach plates that went into binders so
> > they where easier to open.
> 
> No, Jeppesen got their start by Mr. Jeppesen actually producing the first
> charts for making low-visibility arrivals into the airports to which he
> flew.  There were no charts in those days.  He then began sharing them
> with his fellow pilots.  All this happened before the CAA ever got
> involved.

Really? Interasting history lesson, but I was simply making a guess as
to why they now offer electronic stuff.  When the electronic age
started, they where really only a printer just like NOS is now, only
they released things in a bit more user friendly way.  Once the CAA aka
FAA got into the business of approvaing approaches, Jeppesen was then
regulated to provide what was approved..  After all it's the FAA's stamp
of approval that makes the approach legal these days, not the fact that
Mr Jeppesen drew up the approach plate.

> > The paperback NOS plates got difficult to
> > manage in-flight and if you ever dropped your NOS book, it was going to
> > take some time to look up the approach plate again.
> 
> You have the horse before the cart.  Jeppesen charts were not produced in
> response to the NOS charts.  It was actually the other way around.

I don't doubt it.. But at the point where the electronic format started,
what I represneted was basicly true.  Jeppeson was simply an printer of
charts that where better looking and more conveient than the NOS
offerings.  They cost more than the NOS, but being nicer they could make
money doing this.  This has been the case since the CAA aka FAA started
approving insterment approaches and limiting IFR operations to said
approaches.  The CAA may have started printing approach plates as a nice
idea.

> > It went from there to this "electronic" format.  This type
> > of data did not become popular until we started seeing LORAN units, GPS
> > and Internal Nav stuff, but Jeppeson was there when the air carriers
> > started looking for this data in a consistent format, so their format
> > got adopted by the "big boys" long before the average Joe could afford a
> > Loran or GPS unit for their very own, we just where along for the ride.
> 
> Until very recently (if it has ever changed and I don't think it has ...
> yet) the charts were hand-drawn.  They were not generated electronically
> by automatically compiling the data about locations, waypoints, courses,
> etc.  The early "electronic" approach plates were just scanned images of
> the plates since that was the *only* acceptable source of approach data.
> Sure it makes sense to shift off to approach plates synthesized from the
> data (the amount of data required would be a lot smaller too).  One of the
> main reasons for this was that the electronic data maintained by the FAA
> was "dirty" and there was no defined process for cleaning up that data.

Perhaps then the NOS plates are the real "legal" document.  If they are
hand drwan then scanned for printing the FAA data may not be accurate
enough to draw approach plates.  But then one would wonder where
Jeppeson gets their "data".  Perhaps they are using a bunch of guys to
re-draw the NOS stuff?

If that's the case, then it really does not matter what Jeppeson does
with their electronic data.. It's not really any better than the NOS
printed materials, it's just the only electronic source of the data.

Perhaps I am a bit to trusting that the FAA actually generates approved
approach plates and charts using the data they release electroniclly... 
Federal does usually mean slow and behind the times.

> Jeppesen is the only source of which I am aware that has "clean" data.
> Yes, they use the FAA data as input but they do have a process by which
> that data is verified and cross referenced.

I would have to ask, verified and cross referenced agnist what?  See,
this is the problem.  Jeppesen may have independantly obtained data, but
from what source?  Do they scan in the NOS approach plates and use them
as a basis for theirs?  Is the NOS approach plate not covered in the
electronic data we are talking about?  Does Jeppesen have some standard
set of corrections and data integerity rules they enforce that "clean
up" the faulty data from the Government?

Chances are they don't really have much new information... And the NOS
printers are really the source of this stuff anyway.  So we are talking
about two differant types of information.

> > It's the government data that is the "legal" data.  You must fly your
> > Instrument approach using the government verified data on the current
> > approach plate with any NOTAMs taken into account, or it's against the
> > rules.  If Jeppeson takes liberties with the data, and "fixes" something
> > in the government's certified data, then you cannot legally use their
> > approach plate.  Now if they ADD information to the government's data,
> > that's OK.. They just cannot change the certified approaches in any way.
> 
> We may be agreeing violently here.  Certainly the Jeppesen data must be
> verified as correct.  I think that the difference here is that you are
> claiming that, since the FAA uses their data and since they are the
> ultimate authority, that the data they release to the public in electronic
> form MUST be good.  But where we differ is on WHAT data is the proven
> data.

Jeppesen cannot change approaches as they are published in the NOS
books.

I suppose then, we need to answer the question about exactly what data
the government is publishing electronicly and what claims they make
about the accuracy of the data.

If it's usable for real world in route navigation, one would assume that
the data is good enough that you could find your way arround.  If it is
supposed to have approach procedures and can be used as a basis for
percision and non-percision approaches, one would assume that the data
in it is accurate enough to produce an approach plate for the specific
approaches it has data on.

If it does not have approach information in it... We are talking about
differant data sets, and the Jeppeson would be the *only* source of
parts of the data.  

The data that is common, is common..  A new VOR get's added to the FED
data, it shows up in the Jeppeson data..

> The information I had when I was working on this for a commercial project
> was that the only verified data was the approch plate itself, not the raw
> data that was initially used to create the plate.  So if an error is
> discovered in the plate, the correction is applied to the picture of the
> plate and not to the original raw data.  This means that the FAA raw data
> was never fully verified nor guaranteed to be correct even tho' the
> approach plate IS correct.  The plate evolves as the changes are applied
> and there didn't used to be tracabilty back to the raw data itself.

Then, Jeppeson is based on the NOS publication, and simply is a digital
form of that, and we are then talking about differant data sets.

It would be VERY nice to get an accounting of just how accurate the
federal data is...  So like you, I'd love to see perhaps an approach
plate generation program, then we can start an independant verification
that the approach plates we generate either are or are not equivilant to
what the NOS publishes.  When we find data errors, we get them
corrected.. When we have programming errors, we fix them.

Eventually, we will make the government more efficient and the data much
better.. At least in theory.

-- 
      -=  Bob =-
Hey.. This is my mail and I charge for SPAM I receive...
-
Archives of linux-aviation: http://mail.nl.linux.org/lists/linux-aviation/
To unsubscribe: send the command "unsubscribe linux-aviation" in the body
of a mail message to <Majordomo@mail.nl.linux.org>.