Re: New ground proximity warning.

Date:         04 Dec 96 02:42:19 
From: (Robert Dorsett)
Organization: Netcom Online Communications Services (408-241-9760 login: guest)
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In article <airliners.1996.2584@ohare.Chicago.COM> (C. Marin Faure) writes:
>I had an opportunity to see an Alaska Airlines internal communication
>video yesterday, and they described a new terrain avoidance system that I
>think is pretty slick.  It is being installed on their 737-400s and will
>undoubtedly be a feature of their new 737s as well.
>A very accurate terrain map of an area-- in the example on the tape it was
>Juneau, Alaska-- is put on a CD-ROM.

Not to sound trite, but the reliability of such a system is directly related
to the quality of data which goes into it.  I can't help but think of the
large number of "uncharted" swatches on every Cali crash chart I've seen
thus far.  And any cartographer is aware of the huge number of "design
compromises" which go into map-making, and the amount of fudging (inter-
polation between data points, etc) that goes on.

For the purpose that you describe, "accuracy" does not seem to be hugely
important--situational awareness is more important, and one can suffer
significant deviations in the terrain model.  If "accuracy" does start
to assume a role in such systems--for navigationally relevant terrain
avoidance--I'd start to become very concerned.

We need to step away from the "gee whiz" aspect of this type of technology
(which has apparently influenced at least one senior DOT bureaucrat to call
for such devices) and harshly analyze the data set, its intended purpose, and
logically analyze how the current system fails us.  There are likely going to
be solutions out there which are much less expensive (and less glamorous).

Robert Dorsett                         Moderator, sci.aeronautics.simulation