The event algorithm is as follows: 
Competitor’s ranking points,
RP = A - B points where A = Competitor’s score/Winner’s score x 100
and B = (Competitor’s time / Maximum time penalty) x (100 / Winner’s score)
Here is a single example:
A competitor has 17 controls correct with two timed controls = 155sec. The winner had 20 controls correct.
A = 17 / 20 x 100 = 85.0; B = 155/240 x 100/20 = 3.25; RP = 85 - 3.5 = 81.5 pts
For the Ranking list:
The sum of the top 3 Ranking Points for the last 7 ranking events are divided by 3 to determine overall ranking. Apparent ties are resolved to the 4th decimal place. Trail O Event Directors and Course Setters receive a credit equal to their top result.
Key:
Para = Paralympic class,
2011 Orienteering USA Trail O Rankings detailed (xlsx)
Past years:
2010 U.S. Trail O Rankings (pdf) Tied rankings beyond 30 not resolved.
2009 U.S. Trail O Rankings
