// dists is an array of reference objects (properties x, y, z, distance)
// returns an object containing the best candidate found (properties x, y, z, totalSqErr, i1, i2, i3)
// i1, i2, i3 are the indexes into dists[] that were reference points for the candidate
// totalSqErr is the total of the squares of the difference between the supplied distance and the calculated distance to each system in dists[]
private Candidate getBestCandidate(Entry[] dists)
{
int i1 = 0, i2 = 1, i3 = 2, i4;
Candidate bestCandidate = null;
// run the trilateration for each combination of 3 reference systems in the set of systems we have distance data for
// we look for the best candidate over all trilaterations based on the lowest total (squared) error in the calculated
// distances to all the reference systems
for (i1 = 0; i1 < dists.Length; i1++)
{
for (i2 = i1 + 1; i2 < dists.Length; i2++)
{
for (i3 = i2 + 1; i3 < dists.Length; i3++)
{
var candidates = getCandidates(dists, i1, i2, i3);
if (candidates.Length == 2)
{
candidates[0].totalSqErr = 0;
candidates[1].totalSqErr = 0;
for (i4 = 0; i4 < dists.Length; i4++)
{
DistanceTest err = checkDist((Coordinate)candidates[0], dists[i4].Coordinate, dists[i4].Distance);
candidates[0].totalSqErr += err.error * err.error;
err = checkDist((Coordinate)candidates[1], dists[i4].Coordinate, dists[i4].Distance);
candidates[1].totalSqErr += err.error * err.error;
}
if (bestCandidate == null || bestCandidate.totalSqErr > candidates[0].totalSqErr)
{
bestCandidate = candidates[0];
bestCandidate.i1 = i1;
bestCandidate.i2 = i2;
bestCandidate.i3 = i3;
//console.log("best candidate so far: (1st) "+JSON.stringify(bestCandidate,2));
}
if (bestCandidate.totalSqErr > candidates[1].totalSqErr)
{
bestCandidate = candidates[1];
bestCandidate.i1 = i1;
bestCandidate.i2 = i2;
bestCandidate.i3 = i3;
//console.log("best candidate so far: (2nd) "+JSON.stringify(bestCandidate,2));
}
}
}
}
}
return(bestCandidate);
}
// calculates the distance between p1 and p2 and then calculates the error between the calculated distance and the supplied distance.
// if dist has 3dp of precision then the calculated distance is also calculated with 3dp, otherwise 2dp are assumed
// returns and object with properties (distance, error, dp)
private DistanceTest checkDist(Coordinate p1, Coordinate p2, double dist)
{
DistanceTest ret = new DistanceTest();
ret.dp = 2;
/*
* if (dist.toFixed(3) === dist.toString()) {
* // assume it's 3 dp if its 3 dp rounded string matches the string version
* ret.dp = 3;
* }*/
ret.distance = eddist(p1, p2, ret.dp);
ret.error = Math.Abs(ret.distance - dist);
return(ret);
}
// calculates the distance between p1 and p2 and then calculates the error between the calculated distance and the supplied distance.
// if dist has 3dp of precision then the calculated distance is also calculated with 3dp, otherwise 2dp are assumed
// returns and object with properties (distance, error, dp)
private DistanceTest checkDist(Coordinate p1, Coordinate p2, double dist)
{
DistanceTest ret = new DistanceTest();
ret.dp = 2;
/*
if (dist.toFixed(3) === dist.toString()) {
// assume it's 3 dp if its 3 dp rounded string matches the string version
ret.dp = 3;
}*/
ret.distance = eddist(p1, p2, ret.dp);
ret.error = Math.Abs(ret.distance - dist);
return ret;
}
