As part of my slow but sure attempt at entering the competition I have created a simple but effective solution to this part of the rules using a Ray casting algorithm and running this on a Netduino in C# (easy to convert to Arduino).

Here is the code to test if the current location falls within a polygon:

public static bool LocationInsideBoundry(Position point, Position[] boundry)

{

bool insideBoundry = false;

try

{

int j = boundry.Length - 1;

for (int i = 0; i < boundry.Length; i++)

{

if (boundry[i].Longitude < point.Longitude && boundry[j].Longitude >= point.Longitude ||

boundry[j].Longitude < point.Longitude && boundry[i].Longitude >= point.Longitude)

{

if (boundry[i].Latitude +

(point.Longitude - boundry[i].Longitude) / (boundry[j].Longitude - boundry[i].Longitude) * (boundry[j].Latitude - boundry[i].Latitude) < point.Latitude)

{

insideBoundry = !insideBoundry;

}

}

j = i;

}

}

catch (Exception)

{

return false;

}

return insideBoundry;

}

Pretty simple stuff and works a treat.

Here is a simple app in .net that shows if the current location is inside the boundary – drag the map around with the right mouse button add some points and if the location is inside the boundary then the group box background will be green – outside then red.

Hopefully it will be of some use.

Cheers
Justin