# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: Distance Offshore/Introduction**

**From:**Dan Hogan

**Date:**1996 Nov 29, 15:18 EST

Here are some I carry in my NAV Notebook: The following are a collection of piloting formulas and hints I have picked up over the years. I carry them in my Navigation Notebook. The "Distance Off Two Landmarks or Seamarks," was first shown to me by a friend that flew a TBM Avenger in WWII. He said 99% of his navigation to get back to the carrier was dead reckoning. ==========================================================================| | First | Second | Dist. Off | Dist. off | | Bearing | Bearing | Sec'd Bearing | Abeam | ====================================================|=====================| Bow & Bearing | 45 | 90 | Dist. Run | Dist. Run | --------------------------------------------------------------------------| Double Angle | ... | 2 * First | Dist. Run | | --------------------------------------------------------------------------| Seven Eights | 30 | 60 | Dist. Run | 7/8(.875) * Dist Run| --------------------------------------------------------------------------| Seven Tenths | 22.5 | 45 | Dist. Run | 7/10(0.7) * Dist Run| --------------------------------------------------------------------------| Prediction | 26.5 | 45 | 1.4 * Dist Run| Dist. Run | ==========================================================================| TIME/SPEED/DISTANCE ( In Hours, Knots , Nautical Miles) Distance = Speed * Time * ((60, for minutes) or (3600, for seconds)) THE RULE of 60 Distance Abeam * 60 = Bearing on the Bow * Range TIME at 1 Mile = 60 / Speed SPEED = (SQRT Bow Wave Length) * 1.33 DISTANCE at 6 Minutes = 1/10 (0.1) * Speed DISTANCE TO HORIZON = 1.17 * SQRT of HE BREAKERS AT HORIZION = 3 Miles Off WINDOWS VISIBLE = 2 Miles Off COUNT TREES = 1 mile Off ECHO Distance Off = 1/2 Time in seconds * .18 SOUND DISTANCE OFF = Time in Seconds * .18 ************************* FORMULAS FOR CALCULATORS D = distance R = distance run A = First Bearing B = Second Bearing Distance Off at Fiirst Bearing & Run Abeam D = (R x sin A) / Cos A Distance Off Second Bearing Form Second Bearing on Bow & Run D = (R x sin A) / (sin A [abs. diff.] B) Distance Off Abeam with Second Bearing on Bow and Run Betweeen D1 = (R x sin 2B) / sin C D2 = D1 x sin A (D2 = distance off abeam) Distance Run to a Given Bearing & Distance Off When on That Bearing D1 = (R1 x sin B) / sin C D2 = D1 x sin A (D2 equals distance off abeam) ************************************* Sailing to Weather D = (200 / sine of the angle between tacks) * sine attack angle D = percentage of the distance to the mark. attack angle = the angle off the wind when sailing. ************************************* Distance Off Two Landmarks or Seamarks s / SIN LS : a /sin LA : b / sin LB s = distance between marks LS = angle diff between a & b a = distance from ship to b LA = angle diff between bearing of a from ship & bearing of b from a b = distance from ship to a LB = angle diff between bearing from b to a & Bearing b from ship ************************************ Tacking Downwind Total distance sailed = 2 * base distance * sin of the divergence angle/sin (divergence angle * 2) Chart: _____________________________________________________ Divergence | Speed | Distance | Time angle | | to sail | Hrs. -------------|-----------|---------------|----------- | | | -------------|-----------|---------------|----------- Dan Hogan West Covina, CA dhhogan@XXX.XXX