Tutorial: Getting coordinates for your position *Updated*

[Karl Heinrich]

Some time ago I posted my method for plotting (or perhaps converting) your boat's position into coordinates of latitude and longitude,

However, I have since refined the method (or rather improved my bad maths) so that it can be done much more quickly.

If anything is unclear, please let me know.

Converting your position to co-ordinates


The SH3 world as with the real world can be divided into degrees of latitude and longitude, and each of these degrees can be divided into 60 minutes (') of lat/long and of course each minute can be divided into 60 second ("). This means any calculations we do are the same as any for decimal time.

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

1 degree of latitude/longitude = 120 km

And therefore our minutes (') and seconds (") of lat/long:

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

The above aren't essential to know, but useful.

An Illustrated Example
I loaded up a game with the boat in berth at Wilhelmshaven. We will now get the coordinates of this position

Calculating Latitude

First we need to measure the distance of the boat from the Equator.
Measuring from the centre of the boat icon, in our example we get 6420.9 KM north of the Equator



Degrees
We know a degree is 120km so to break our measurement into degrees we do the following division:

6420.9 / 120 = 53.51

The whole number gives us our degrees, so here it's 53 degrees North. We can start filling in our position:

53° __ __ N, __ __ __ __

Minutes

From the above division we still have 0.51 remaining. To calculate our minutes we simply multiply this by 60:

0.51 x 60 = 30.6

The whole number gives us our minutes, here it's 30 minutes. So adding this data to our position we now have

53° 30' __ N, __ __ __ __

Seconds

Last but not least, we need to know our Seconds of latitude. As before, we have a remainder of 0.6 from the calculation above. To turn this into seconds we multiply by 60. So:

0.6 x 60 = 36

Giving us in this example 36 seconds. We now have our complete latitude.

53° 30' 36" N, __ __ __ __

Calculating Longitude

We do exactly the same as above, but measured from the Prime Meridian, to get our Longitude.

Measuring from our boat in Wilhelmshaven, we get 973.2 km east of the Prime Meridian



Degrees

973.2 / 120 = 8.11

So, 8 degrees. We can add this to our position

53° 30' 36" N, 08° __ __ E

Minutes


0.11 x 60 = 6.6

So, 6 minutes

53° 30' 36" N, 08° 06' __ E

Seconds

0.6 x 60 = 36

So, 36 seconds. We now have our complete longitude and our full position plotted

53°30'36"N, 08°06'36"E

This can now be used in Google Maps, the Naval Grid Calculator or map software of your choice (ensure the format is the same as above with no spaces except after the comma for the Grid Calculator).

In Summary in 6 Steps
1. Measure Position from Equator
2. Divide result by 120. The whole number is degrees of Latitude
3. Multiply any remainder by 60. The whole number is your Minutes (') of Latitude. If there is no remainder mark 0'
4. Multiply any remainder of by 60. The number is your Seconds (") of Latitude If there is no remainder mark 0"
5. Ensure you denote North or South of the Equator.
6. Repeat the steps above with a measurement from the Prime Meridian for Longitude, denoting East or West respectively.

Using the example above in Google Maps, we are the green arrow.

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

[Karl Heinrich]

Thanks, it's been a few years since my last post on this but finally have some time to devote to my charts project again!

That is a very nicely programmed tool indeed BL!TZKR!EG, I did create an Excel version for my method a while back, but as we try to do 'paper' navigation only (as below on my custom made charts) with the boat icon invisible in our 'multiplayer' games I decided against using it. We definitely need to get involved with DEF though! I love that online map, very reminiscent of the Virtual Airline ones but much cooler

[Tycho]

Now, when my game counts the degrees, your method is even more quick.



I just measure the distance from the position to the appropriate degrees.
Divide by 2, to get the minutes.
The rest, multiply by 60 to get the seconds.

On these screens:





7° + 87 km and 478 m
87.478 / 2 = 43.739
43'
0.739 * 60 = 44.34
44''
=
07°43'44"E

Usually, in order to do the calculation more easy in mind, for the seconds I move decimal point and multiply by 6, like this:

0.739 > 7.39 or 7.4 * 6 = 44.4 = 44''

The result is the same.

Originally Posted by Tycho

Now, when my game counts the degrees ...

Wow, will you update your download link here : http://www.subsim.com/radioroom/showthread.php?t=231140 ?

[Tycho]

Originally Posted by Kendras

Wow, will you update your download link here : http://www.subsim.com/radioroom/showthread.php?t=231140 ?

What to update? The link is ok and this feature is already there.

[Leoz]

Originally Posted by Tycho

Now, when my game counts the degrees, your method is even more quick.



I just measure the distance from the position to the appropriate degrees.
Divide by 2, to get the minutes.
The rest, multiply by 60 to get the seconds.

On these screens:





7° + 87 km and 478 m
87.478 / 2 = 43.739
43'
0.739 * 60 = 44.34
44''
=
07°43'44"E

Usually, in order to do the calculation more easy in mind, for the seconds I move decimal point and multiply by 6, like this:

0.739 > 7.39 or 7.4 * 6 = 44.4 = 44''

The result is the same.

All very impressive. Thanks for this.

Off-topic, what is that interesting map / main layout mod you are using?

Thanks in advance.

[Tycho]

Originally Posted by Leoz

Off-topic, what is that interesting map / main layout mod you are using?

How the map looks is depend of two files. Terrain.act, that determines colors for different water depths and different terrain highs.
And StrTactMap.tga, that is transparent layer over the map and is supposed to give feeling of paper.
There have many variants of these files, on my screenshots are from my Tycho Sh3 Patch, you can use these even without patch itself.

Please, learn to not quote the whole post, if it is big or with many images, very annoying to scroll again the same post.