ARC_CALC_3 — Spherical Trigonometry Calculator by James Q. Jacobs




Most spreadsheet programs should be able to import this file format. The graphic below illustrates the spreadsheet, before corrections in 2002. Previous downloads have "A to C" and "B to C" labels swapped for arcs and bearings. Please let me know if there are other bugs in the applet. Epoch_Calc Temporal Epoch Calculator
is a similar Excel spreadsheet. It calculates
NEW: Google
Earth™ Ancient Monuments Placemarks
Newark Archaeogeodesy 

Spherical
Trigonometry Note: a and b are distinct from a (alpha) and b (beta). 1. Find distances a and b in degrees from the pole. 2. Find angle P by arithmetic comparison of longitudes. (If angle P is greater than 180 degrees subtract angle P from 360 degrees.) 3. Solve for 1/2 ( a  b ) and 1/2 ( a + b ) as follows: tan 1/2 ( a  b ) =  { [ sin 1/2 ( a  b ) ] / [ sin 1/2 ( a + b ) ] } tan 1/2 y4. Find c as follows: tan 1/2 c = { [ sin 1/2 ( a + b ) ] x [ tan 1/2 ( a  b ) ] } / sin 1/2 ( a  b )5. Find angles A and B as follows: A = 180  [ ( 1/2 a + b ) + ( 1/2 a  b ) ] 
