Perry Mick wrote:

Paul wrote:

That is tricky to use that data as you need to be competent
in spherical trig. Plus the lat/long resolution is not the greatest.

Easier way is to sneak out there in the middle of a foggy moonless night
with a 100 foot tape and a spray can of white paint :-)

Or talk to the airport manager and ask him how far apart are the
runway lights.

I see no problem carrying an observer as you don't need to take
off. A simple stop watch will do. Make separate runs to each
100 foot marker so the observer has only one time to record
during each run. Too bad I don't have one of my computerized fifth
wheels lying around like they used on the Rutan Voyager.

Once we have a plot of acceleration up to 85 Kts we can extrapolate
that to 100 Kts or so hopefully things are roughly linear up to
at least that speed. I suspect however as the fan tips approach
mach .8 or above things get decidely non-linear.

It's much simpler than that, you don't need to use spherical
trig because the earth is basically flat within the confines of
the airport.  I already worked out the numbers.  1 minute of
latitude = 1 nm = 6076.115 ft.
1 minute of longitude at 45 degrees, 11.5 minutes north is
6076 * cos (45 + 11.5/60) = 4240 ft.
By my calculations:
Runway 4 is 5305 ft. long, the total length including the
threshold is 6171.  But trying to get 100 foot resolution with this
method may not be very accurate, as you say.

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