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Karl Heinrich · 07-04-13, 05:24 AM

No problem, LemonA.

Again, "doubled angle on bow" is generally less accurate in coastal nav than two point (or more) cross fixes. But if you only have one landmark, it can be useful like running fixes (Although I prefer the latter).

Again the most difficult thing is finding a clearly identifiable bit of land.

The Actual Explanation

Basically, you take a bearing of the landmark when it's at a nice round number (not essential of course) and under 45 degrees, e.g. 20 degrees. Plot this on the map across your dead reckoning course/track line. Note time and speed as always.

Proceed along the set course and keep an eye on this landmark, when it reaches 40 degrees in this example, note the time and plot another position line. Consulting speed/distance charts calculate the distance travelled. In this case, say it's 12km.

This works because it generates an isosceles triangle, so the distance between your boat and the second bearing taken is the same as the distance travelled. So 12km down the second bearing position line is where your boat is. If you're on couse this should pretty much be where the second bearing position line and your intended course line meet.

The alternative is the Four Point Bearing - same procedure, but the first bearing must be taken at 45 degrees and the second at 90 degrees.

~~~

Apologies it's a bit of a rough explanation, I'll do a proper one with pretty pictures soon - for some reason the screenshot function in SH3 wasn't working before but is now.

I'll put together some revised guides shortly, this one was a little more haphazard than intended. If I can get FRAPS working I'll do it as a video tutorial.

If anyone knows to what extent wind affects position it would be appreciated, need to do more tests on this to calculate "set and drift".

I know time compression affects speed as wel (but only in rough seas it seems), I recall Vanjast suggesting it was around 15% increase, and my single test so far has shown it to be 14% (so near enough).

I'm also planning a world and map mod that adds more notable landmarks (lighthouses etc). to the landscape - assuming this is feasible. The intention is to focus on a relatively small area first. Where possible these will be historically accurate

07-04-13, 05:24 AM	#3
Karl Heinrich Soundman Join Date: Nov 2012 Posts: 146 Downloads: 60 Uploads: 2	No problem, LemonA. Again, "doubled angle on bow" is generally less accurate in coastal nav than two point (or more) cross fixes. But if you only have one landmark, it can be useful like running fixes (Although I prefer the latter). Again the most difficult thing is finding a clearly identifiable bit of land. The Actual Explanation Basically, you take a bearing of the landmark when it's at a nice round number (not essential of course) and under 45 degrees, e.g. 20 degrees. Plot this on the map across your dead reckoning course/track line. Note time and speed as always. Proceed along the set course and keep an eye on this landmark, when it reaches 40 degrees in this example, note the time and plot another position line. Consulting speed/distance charts calculate the distance travelled. In this case, say it's 12km. This works because it generates an isosceles triangle, so the distance between your boat and the second bearing taken is the same as the distance travelled. So 12km down the second bearing position line is where your boat is. If you're on couse this should pretty much be where the second bearing position line and your intended course line meet. The alternative is the Four Point Bearing - same procedure, but the first bearing must be taken at 45 degrees and the second at 90 degrees. ~~~ Apologies it's a bit of a rough explanation, I'll do a proper one with pretty pictures soon - for some reason the screenshot function in SH3 wasn't working before but is now. I'll put together some revised guides shortly, this one was a little more haphazard than intended. If I can get FRAPS working I'll do it as a video tutorial. If anyone knows to what extent wind affects position it would be appreciated, need to do more tests on this to calculate "set and drift". I know time compression affects speed as wel (but only in rough seas it seems), I recall Vanjast suggesting it was around 15% increase, and my single test so far has shown it to be 14% (so near enough). I'm also planning a world and map mod that adds more notable landmarks (lighthouses etc). to the landscape - assuming this is feasible. The intention is to focus on a relatively small area first. Where possible these will be historically accurate __________________ “Die Südfrüchte runter vom Kartentisch. Auf Bananen kann ich nicht navigieren.” Last edited by Karl Heinrich; 07-04-13 at 10:32 AM.