[don1reed]

Dang, Pisces, you're making me feel like "johnny appleseed". I'd forgotten that I told you about HOMOTO. Just another sign of old age, I suppose. lol

TorpX: The F5 screen in the game is not based on a true Mercator Projection Chart. The Developers had to come up with a system to be able to fit the ocean on your display.

This is why it's imperative to do a save every time you take a sight. Saving, updates your boat to it's true Lat/Long, so when you view the celestial canopy in Stellarium, you are seeing the heavens as if you were really at that location in RL.

In the game, DR positions are always wrong. Unless....

you fudge the numbers.

In RL, if I travel @ 10kn. for x hours, I can measure 10 nm along the Latitude hacture marks on the left or right side of my chart with a pair of dividers, then walk the dividers along my drawn course line to see where my DR position is. You cannot do that with the F5 charts of SH3/4/5.

To compensate, you can use the formula

Nautical miles x cosine (whole degree) Latitude = distance.

i.e.,

In RL I'm making 10kn for 5 hours . Distance = Speed x Time = 50nm
In game 50nm x cos 28* = ~44nm.

I used 28 degrees as an example. I play SH3 predominately so lets say I'm near Fair Isle in the North Sea and my Assumed Lat is ~59 degrees, then the formula would reveal:
50nm x cos 59* = ~26nm.
~26nm is the distance I would travel in the game at a speed of 10 knots for 5 hours.

Since we're dealing with deducted reckoning it's the only way I've been able to fudge the numbers to get my DR position.