# Thread: Find coordinate given distance

1. ## Find coordinate given distance

Hello everybody. I have the following problem:
I have a position as a coordinate (lat, lon). Imagine it as a point on a ship somewhere located via AIS. That's a coordinate that I store in my c# objects as a MapPoint.
Then I know that the ship is, say, 100 meters long, and is moving at 30° bearing respect to the north. Ok.
Now I suppose that the AIS is mounted on the aft of the ship, and want to compute where is the fore of the ship. So I take the coordinate and want to move 100 meters along a bearing 30° to a new coordinate. How do I find the new coordinate? Both client and server solution are appreciated, but I'll value extremely the client based solution because allow me to be largely independent from a lot (really a lot) of remote queries. I don't need great precision, just an hint could suffice. Could be precise up to a meter, but even far less.

I'm doing this because I want to give a graphical perception of the dimension of a ship. So I'lll then draw on the map a rectangle with the dimensions up to the coordinates I found, simulating a (very dull) ship hull.

What do you think? Is it feasible? Is it easy? If it would be to find distance given coordinates I would have used a geometry service, but it looks like there is no inverse functionality (from distance to coordinates) available. Is there an easier way to build the shape?

2. ## Re: Find coordinate given distance

If it is ships and AIS i guess you are working in WGS84 geographics coordinates (in projected like UTM you can just use plain trigonometri for approximate calculations).

For geographicals you will find a lot of useful formulaes here: http://www.movable-type.co.uk/scripts/latlong.html

The formulaes operate with a spherical earth, but I guess that should be ok for approximate calculations