LFSD West Coast Challenge 2005
Long Flights On Short Days
Original posting 12/31/04
Z Adjustment Factor Expression
To calculate a score, we multiply the miles flown times a calculated adjustment factor "z" to devalue longer days. In 2004, we used to use a simple expression that resulted in an elegant curve, but the outcome seemed to favor flights near the equinox, so for 2005 we gave the expression 4 exponent "tool handles" to control the curve shape. Since there is a seasonal lag we use an "if" statement to select separate formulas for waxing and waning days. Each formula contains 2 exponent handles that we use to adjust the shape of the curve. There is interaction between the exponents, but one is used to "stretch" the top of the curve around the solstice and the other is used to control the slope (steepness) through the equinox.
The expression was assembled in an Excel Spreadsheet "Calculator". You can go to the graph page and play with the curve shape by changing the anchored exponent reference cell values. We labeled the cells to make it easier to logically follow the math.
2005 Exponents: se=2.0, de=16, re=2.2, ce=26
Exponent Selection: The focus was to make the curve work in the prime months where our South Coast flying has an advantage over other sites. Early November through early March. Longer flights will be had from SB in April, but flat land sites have historically posted bigger numbers by mid spring. The expression for 2005 was frozen on 12/31/04, but in future years we may choose to tweak the curve down for late winter if Diablo continues to push out further in the desert flats early in the season.
Negative Cosine Values: There are some negative cosine values for days 181 through 185, but the effective z output on those days utilizing the exponent values for our purpose is zero, so the negative values have no real effect and we choose to ignore them to make the calculation simpler. We could force the negative values positive, but that would entail extra clunkiness. The next time someone creates our universe, if they could make our year 360 days instead of 365¼ day, life would be a little easier.
Rounding: "z" is displayed to 4 decimal places, but is calculated to more precision within our calculator. Miles are displayed to the nearest mile. The calculator can display more precision, but we will score to the nearest mile displayed by the calculator. Miles will be input to the nearest mile. This seems like a reasonable resolution, especially for the few dinosaurs that haven't incorporated a gps. The compounding of rounding errors could permit a shorter flight to win, but it's not a perfect world and its only a game for fun. Reaching pilots will do well over numerous seasons.