I figured this is sort of on topic: it is a method that I read in an old book on 'cold wx flying' by someone named Jefferey Griffin:
it is a method for estimating inflight visibilty from 'normal eye level'
1. sit in your aircraft; with the aircraft at a level normally used for flight make a mark with a piece of tape on the side window at the level of your eye, measure the heigh of the mark from ramp level
2. have someone place an orange cone at a distance where you can just see it,
looking down the nose of the plane
3. compute the TAN value [opposite length over adjacent]
ex: your mark is 6 ft and your distance measured is 30 TAN = 6/30 =.20
the tangent value can then be correated to in flight slant range visibility
Now, I'll have to put the values of TAN vs visibility tomorow as I don't have it before me now.
in the form Tan Value, angle theta in degrees, approx inflight vis
at 1000'agl:
0.052,3,19200; 0.070,4,14280; 0.087,5,11500; 0.105,6,9530; 0.123,7,8130; 0.141,8,7090; 0.158,9,6330; 0.176,10,5750; 0.194,5150; 0.213,12,4710; 0231,13,4320;0.249,14,4010;
0.287,16,34800.306,17,3270; 0.325,18,3070; 0.344,19,2910; 0.364,20,2750
this method is useful for those flying 'GA' in order to make a decision if continued VFR is a good Idea,....but I though it would be nice to pass this nice Idea along,...sorry about the values I'm not home
PA