When you decide to shoot the stars, click on the stopwatch immediately after the minute on the clock changes. This allows you to know Greenwich Mean Time to about 5 second accuracy in game. Earlier in the thread is a discussion on how the game clocks work, and how to get GMT from your local time and the nautical time zone. Here I am using my nautical chart with 1° grid spacing. SH3 world is a cylinder with 120 km between latitudes and longitudes. We will eventually need to correct our result for this map projection.
Select navigation stars with bearings roughly 120° apart, so you will get a nice shaped error triangle when you are done. I chose the first star on the list, Alioth, and then used its bearing to help choose the other 2 stars. You will need a minimum of 2 stars, but everyone uses 3. When you shoot a star, you measure its altitude or height above the horizon. This is called Hs. You then make the reading more accurate by applying correction factors. We have identified two corrections for measurements done with the in-game sextant. The index correction adjusts for a the sextant not being zeroed. It gives us the Ha, or apparent altitude of the star. The second corrects for the distortion in the SH3 camera. I am calling that the Altitude correction. You look it up on the table I created based on the calibration curve I measured. Now you know the observed altitude or height above the horizon Ho. You don't need to record the bearing to the star. But you do need the time of measurement. My measurements were taken 2 minutes apart.
Our position is shown on the map, so we can judge the result.
