Tutorial: Work out your precise coords in SH3

[Karl Heinrich]

Apologies if there is already a thread for this, but I thought I'd share some of the work from my top secret nav project

Now you can always use the black and white border marks to work the method below to work out minutes and seconds of lat/long. Unless you're using a map with coords on, the method below is probably the quickest way overall.

It might look a little convoluted but it's really simple once you've tried it a couple of times.

Please feel free to give it a try, I'd love to see your results. If anything is unclear at all, just let me know

How to work out your precise Long/Lat Coords in SH3

First we need to know the following key measurements.

SH3 uses equirectangular projection for its game world so the distance between each degree of latitude and longitude is exactly the same. However, the devs made it slightly larger than the real world, so we need to work from the following:

1 degree lat/long = 120km

And for our minutes and seconds of lat/long:-

0.0333km = 1"
0.1km = 3"
0.5km = 15"
1.0km = 30"
2.0km = 1' 0"

You can fill the blanks in later.

Where does it work?
This should work anywhere on the map, and as I have used SH3 measurements it should still be proportional to the real world, so you should be able to put your results into Google Maps and get the same spot.

I'm sure with a bit more testing we can break it...

An Illustrated Example
I loaded up a game with the boat in berth at Wilhelmshaven. For simplicity's sake.

Longitude

Using the ruler tool I then measure from the boat to the Prime Meridian



This gives us 973.2 KM east of the Prime Meridian



We now need to break that into degrees, we know a degree is 120km so:-

973.2 / 120 = 8.11

So we know that we are at E08 (E because we are east of the Prime Meridian).

But now we need to convert the remainder 0.11 into Minutes and Seconds

To get 0.11 as a measurement of km we multiply it by 120:

0.11 x 120 gives us 13.2km

We know using the measurements at the start that 2km is 1' (minute) of Lat/Long in SH3

It's easier to work from the highest even number, so leaving the 1.2 for now, 12 / 2 = 6. So that's 6 minutes of longitude.
We can now update our co-ords to E08 6'

But there is still the pesky 1.2 remaining.

We know 1km is 30” (seconds), and 0.1km is 3” of Lat/Long, then 0.2 is 6”

So our 1.2 gives us 36”

So our full Longitude is E08 6' 36”

Latitude

We do the same from the Equator to get our Latitude.



So here we have measuered 6420.9

6420.9 / 120 = 53.51

So, again we know that we are N53 (because we are north of the equator).

The remainder is worked out as 0.51 x 120 = 61.2km

For my simple brain I work this out at 60 / 2 = 30'

The remainder 1.2 if 1km is 30” and 0.2 is 6” gives us 36”

This gives us a complete Latitude of N53 30' 36”

Our full co-ords are then: E08 6' 36” N53 30' 36”

Pop that into Google Maps... We are the green arrow













So please give this a try yourself and let me know your results, it would be good to see a screenshot comparison.

It is worth noting here that in the background of the game, distances are measured to 3 decimal places, the ruler only provides us 1 decimal place.

This means the maximum margin of error is 66.66 metres or 2” (seconds) of lat/long. For our purposes that's nothing at all. It is almost exactly 1 boat length of a Type VII.

[raymond6751]

Genius is not a word I throw around much, but your location plan is that.

I thought of asking if it would be the same in SH5, but realize that I could just give it a try myself.

Thanks, good sir, and happy holidays to you!

[Karl Heinrich]

That's very kind Raymond, thanks. It's always nice when the effort put into working these things out pays off. I'm just happy that it works!

I'm not sure if it would in SH5, unfortunately I don't have it otherwise I could check it quickly. If you do try it I'd be very interested to know the results

Thanks again and happy holidays to you too

[Gustav Schiebert]

So THAT'S how it's done... you could get drummed out of the Navigator's Magic Circle for sharing this you know - very impressive stuff as always, when we're navigating on our hotseat games I want to be no more than ten boat lengths out after three months at sea without sun or stars...

[Karl Heinrich]

Haha, damn it. But thank you muchly sir. Alas like most tricks it is disappointingly simple when you know how, but still rather useful for logging your position.

Hmm ten boat lengths you say, we'll see about that but I suspect we'd more likely end up waving at Thomsen...

[Karl Heinrich]

I've tried to streamline the process here, no images this time so refer to the first post for those if necessary. Again if anything is unclear it's almost certainly my fault, so just ask.

How to work out your position in co-ordinates

Key Data:

• 1 Degree of Longitude / Latitude = 120km
• 0.03km = 1” (second) of Longitude / Latitude
• 0.1km = 3”
• 0.5km = 15”
• 1.0km = 30”
• 2.0km = 1' 0”

1. Measure the distance of your boat from the Prime (Greenwich) meridian using the ruler tool. Keep it as straight as possible. Don't worry if it's slightly wonky.

Example: We measured from the boat in berth at Wilhelmshaven to the Prime Meridian. Our result was 973.2km east of the Meridian.

2. Break the distance down into degrees. As a degree of long/lat in SH3 is 120km, we divide the measured distance by 120.

The whole number then provides us the degree of longitude.

Example: As our measured distance was 973.2km, to need to divide this by 120. So, 973.2 / 120 = 8.11. As the whole number is 8, our degree of longitude is E08.

3. Convert the remainder from Step 2 back into km. To do this, multiply by 120.

Example: Our remainder from Step 2 is 0.11. We convert this into km: 0.11 x 120 = 13.2. So we have 13.2km

4. Convert our remainder distance into minutes, referring to the Key Data. Starting with minutes - 2km is 1' (minute) of long/lat. It is easier to take the highest even whole number from your Step 3 result and divide by 2.

Example: With our result of 13.2, the highest even number is 12. We convert that into minutes: 12 / 2 = 6. So we have 6' of longitude. Our current coords: E08 6'

5. Referring to the Key Data we need to convert the final remainder into (minutes and) seconds. Once this is done we have full longitude.

Example. From the 13.2 we have 1.2km yet to be converted. Referring to the key data we can see that 1km is 30” (seconds) and 0.2km is 6” seconds, so we have 36” in total.

Our full longitude is then E08 6' 36”

6. Carry out steps 1-5 again for latitude, but instead of measuring from the Prime Meridian in Step 1 we measure to the Equator.

Note: when measuring longitude, the rule can be drawn slightly above you position, for latitude you need to draw the ruler from on top of your position.

7. Put the final two results for longitude and latitude together, starting with longitude. Congratulations. You now have your full coords. They should look something like this:

E08 6' 36” N53 30' 36”

There are slightly different formats that we can present this in, but this will work if you put it in Google Maps or similar.

[Gustav Schiebert]

I had a go at this:

Figures in green are my measuring
Figures in yellow are arbitrary coefficients from the instructions
Figures in red are the answers

Measurements

• 8866.5km West of Meridian
• [COLOR="rgb(46, 139, 87)"]4764.2km[/COLOR] North of Equator

8866.5km / 120 = 73.8875

73 means I'm at 73W

0.8875 x 120 = 106.5km extra

106 means I've got 53' (106 / 2 = 53)

The 0.5km left over is 15" (1km = 30", therefore 500m = 15")

W73 53' 15"

4764.2km / 120 = 39.702

39 means I'm at 39N

0.702 x 120 = 84.24km extra

84 means I've got 42' (84 / 2 = 42)

The 0.24 left over is 7"

N39 42' 7"

W73 53' 15" N39 42' 7"



Which is bang on - although my maths may not be.

[Karl Heinrich]

Your maths look spot on to me sir.

Hopefully the instructions were pretty straightforward, and very glad it worked.

Now that I've done it a few times the time it takes is reduced to less than a minute start to finish so it's not too galling a process for me.

I think the next test is to try it near the poles and equator, but whilst we may get accurate coords the horizontal stretching of the equiretangular projection might make it difficult to compare to the mercator of Google maps.

[flag4]

...if only I had the brains...

looks great fun though.

[Karl Heinrich]

Flag4 if I can do it, anyone can My brain doesn't really do maths at all...

[ExFishermanBob]

I've knocked up a small program based on Heinrich's calculations (it will also launch maps.google.co.uk based upon the lat-long, if you wish it to).

You can find it here:

http://www.file-away.co.uk/latlongcalc.exe

(Edit)
It's a Python / Qt program, so if anyone wants it for Linux or Mac let me know.

[danzig70]

I used 100 meters = 0.000833333 degrees in a c++ program I wrote and it seemed to work pretty well.

[Svonne]

This is great! Thanks for this tutorial (and the program).

I tried to get screen shots of trying this in my game but every time I hit print screen my game crashes...

[Pisces]

Originally Posted by Svonne

This is great! Thanks for this tutorial (and the program).

I tried to get screen shots of trying this in my game but every time I hit print screen my game crashes...

Either you are using a widescreen resolution mod.


Or you have Windows Vista/7/8 and the game is installed into the Program Files folder somewhere, and the game is not run using an administrator useraccount.

[Karl Heinrich]

Wow, that's bloody brilliant ExFishermanBob... downloading it now! I'd considered doing that myself, but as I do "paper nav" it was handy to have the sums. Plus I'm a rubbish programmer

Glad you found it useful Svonne, hope you get the issue fixed, would love to see that it actually works when others use it

I'll have to give that a try Danzig