How different is aviation GPS?

Peter Duniho wrote:

That is correct. The presumed 50 meter accuracy is constant throughout the
flight. It's not as though it's additive for each waypoint (or worse, as a
continuous function along the flight). Though frankly, even if it were,
you'd only be off by 500 meters after 10 waypoints which is still "no big deal".

Now I know why planes occasionally land on the wrong runway in IFR
conditions )

As for equipment skids and such, since I don't know the details of your
industry I can't really comment on that. But it seems to me that if you
require that level of detail and are using GPS to accomplish it, you must be
dealing with positioning these skids at a significant distance from wherever
they are referenced to. Otherwise, I'd think one would use more
"conventional" surveying techniques to determine position, orientation, etc.

When I began my career, there were only conventional surveying
equipment. These days, however, rarely do you get a client in the oil
and gas industry who'll accept anything but a GPS survey. Btw, we
engineers are barred too from all surveying, although we're responsible
for supervision and copping attendant liabilities. The actual task
itself is carried out by qualified surveyors who do nothing else

Ramapriya

wrote in message
oups.com...
Now I know why planes occasionally land on the wrong runway in IFR
conditions )

Well, for what it's worth, wrong-runway (or even wrong airport) landings are
much more common in visual conditions, when the pilot is trusted to find the
runway himself.

Flying an ILS involves tuning a radio to a frequency that is specific to the
runway. If an airplane winds up in a position to land on the wrong runway,
then the ILS indication will be so far off that the pilot should be flying a
"missed approach" (that is, aborting the approach to try again).

In visual conditions, simple human error can result in landing in the wrong
place. In instrument conditions, there needs to be a series of poor
judgment decisions on the part of the pilot (or the simple error of tuning
the wrong frequency into the ILS receiver, of course ...but that's not an
"accuracy of guidance" issue, so it doesn't seem relevant in this
discussion).

Pete

wrote in message
oups.com...
Peter Duniho wrote:

That is correct. The presumed 50 meter accuracy is constant throughout
the
flight. It's not as though it's additive for each waypoint (or worse, as
a
continuous function along the flight). Though frankly, even if it were,
you'd only be off by 500 meters after 10 waypoints which is still "no big
deal".

Now I know why planes occasionally land on the wrong runway in IFR
conditions )

As someone already mentioned, the error is not cumulative. Then, too,
approach GPS is a different animal from enroute.

Now I know why planes occasionally land on the wrong runway in IFR
conditions


You do? I don't. In fact, I don't think they do. That happens in visual
conditions.

--
Thomas Borchert (EDDH)