[chbot] Arduino navigation sketch

[Charles Manning]

On Monday 21 February 2011 18:53:53 Noel Grant wrote:
> Hello
> I need some help to create a sketch to steer a model boat though a few
> waypoints from a GPS.
>
> This is a hobby project but I am willing to pay a negotiated fee.
>
> I do not think its a difficult job for an experienced programmer, but thats
> certainly not me. It involves UTM calculations, and steering control.
>
> I have a Uno & Em406 GPS.  I will need a compass, but have not decided on a
> model yet. Please let me know if you are interested in learning more.
>

What do you mean by a sketch?

There are multiple ways to achieve this and the best/easiest approach will 
depend largely on how big an area you want your boat to roam over. You say 
model boat so I expect you're wanting to stay with small distances. If you 
want to sail around the world then you need to do far more complex 
calculations.

The easiest way to handle small distances (ie. smaller than approx 500km and 
not too close to the North or South pole and does not cross the international 
date line) is to use local tanget plane (LTP) calculations.

A local tanget plane assumes the world is flat which is a reasonable 
approximation.

A LTP has a start point and then works with metres East, North and Up (ENU) 
relative to that point. Calculations are then just simple planar 
trigonometry.

Do you really need a compass? That will help when you're moving at slow speeds 
and close in to obstacles but once you're moving at reasonable speeds (0.5 
m/s or so) the GPS heading will be sufficient.

If you want help with getting from NMEA (GPS data ) to LTP then give me a 
yell.

-- Charles