# ET and MPH Environmental Correction By Bowling

The purpose of this program is to correct quarter-mile Elapsed Time (ET)
and Miles-per-Hour (MPH) to Standard Conditions. This is useful in comparing
ET/MPH values obtained at different environmental conditions, and for
predicting what a car will run at a given environment. The inputs are
temperature in degrees F, barometric pressure in inches of mercury, and
percent relative humidity, as well as the measured ET and MPH.
To use this program as a predictor for dial-in times at the track, simply
correct a run to standard conditions, using the "Correct To Standard" option,
and record these values. Next, enter these new values into the ET/MPH inputs,
set the environmental variables to the new "environment", choose the
"Correct To Environment" option, and hit compute.

### Algorithm:

The general equations for this calculation are the following:
cfet = 0.9986 + 0.0095 * (CorrBaro - 29.1) - 0.0002556*(Temp - 35.0)
cfmph = 1.0003525 - 0.00975 * (CorrBaro - 29.1) + 0.0002667*(Temp - 35.0)
For Correction TO Standard:
Et = EtOld * cfet
Mph = MphOld * cfmph
For Correction FROM Standard:
Et = EtOld / cfet
Mph = MphOld / cfmph

These equations were obtained from a empirically-derived correction chart,
which was fitted to the above form (least-squares).
Special "thanks" to Eric Thaxton (thaxton@ksccdun6.ksc.nasa.gov) for straightening out the nomenclature
errors on this page!

More special "thanks to Eric Thaxton (again) for finding a sign error
in the MPH correction.

Bruce Bowling

bbowling@earthlink.net

Bowling Superior