Howdy jmr,
rfix = running fix
The formula:
Long cos Lat is actually
Minutes of longitude x cos Degrees of latitude
I only abbreviated the formula (
sorry)
Caveat:
Just be aware when using this little gem of a formula on an 8.5" x 11" sheet of paper that it will only be accurate for about 2 degrees (120 nm). As a result, around here I go through a lot of paper.
Cheers,