/// <summary>
/// Return visibility report from first point to last point. We assume that all points are aligned.
/// WARNING: those calculations are not spherical (yet) and are not accurate for long distances.
/// <see cref="IntervisibilityMetrics"/>
/// </summary>
/// <param name="points">Input list of points, visibility is calculated for first and last points (ie: are they visible or is there a relief standing in between)</param>
/// <returns><see cref="IntervisibilityMetrics"/> object</returns>
internal static IntervisibilityMetrics ComputeVisibilityMetrics(IList <GeoPoint> points, bool visibilityCheck = true, double sourceVerticalOffset = 0d, double targetVerticalOffset = 0, double?noDataValue = null)
{
IntervisibilityMetrics metrics = new IntervisibilityMetrics();
if (points.Count == 0)
{
return(metrics);
}
GeoPoint A = points.First(), B = points.Last();
double hA = A.Elevation ?? 0d, hB = B.Elevation ?? 0d;
hA += sourceVerticalOffset;
hB += targetVerticalOffset;
double AB = A.DistanceTo(B);
visibilityCheck = visibilityCheck && (AB > double.Epsilon);
if (hA < hB)
{
MathHelper.Swap(ref A, ref B);
MathHelper.Swap(ref hA, ref hB);
}
double total = 0, minElevation = double.MaxValue, maxElevation = double.MinValue, totalClimb = 0, totalDescent = 0;
GeoPoint firstPoint = points[0];
firstPoint.DistanceFromOriginMeters = 0; // force at 0. If null, ignored in json responses
double lastElevation = firstPoint.Elevation ?? 0;
IntervisibilityObstacle obstacle = null;
double lastPeakElevation = 0;
int numNoDataPoints = 0;
for (int i = 1; i < points.Count; i++)
{
#region metrics
GeoPoint curPoint = points[i];
double v_dist = DistanceTo(curPoint, points[i - 1]);
total += v_dist;
curPoint.DistanceFromOriginMeters = total;
minElevation = Math.Min(minElevation, curPoint.Elevation ?? double.MaxValue);
maxElevation = Math.Max(maxElevation, curPoint.Elevation ?? double.MinValue);
numNoDataPoints += curPoint.Elevation == noDataValue ? 1 : 0;
double currentElevation = curPoint.Elevation ?? lastElevation;
double diff = currentElevation - lastElevation;
if (diff > 0)
{
totalClimb += diff;
}
else
{
totalDescent += diff;
}
#endregion
#region visibility checks
// Visibility check
// If obstacle hit, add it and
if (visibilityCheck)
{
double distToLowestPoint = curPoint.DistanceTo(B);
double visibilityElevationThreshold = (distToLowestPoint * (hA - hB)) / AB + hB;
if (currentElevation >= visibilityElevationThreshold)
{
if (obstacle == null)
{
obstacle = new IntervisibilityObstacle(curPoint, visibilityElevationThreshold);
lastPeakElevation = currentElevation;
obstacle.PeakPoint = curPoint;
}
else
{
// still inside obstacle, find peak
if (currentElevation > lastPeakElevation)
{
lastPeakElevation = currentElevation;
obstacle.PeakPoint = curPoint;
}
}
}
else
{
if (obstacle != null) // out of obstacle, register it
{
obstacle.ExitPoint = curPoint;
metrics.AddObstacle(obstacle);
obstacle = null;
}
}
}
if (i == points.Count - 1 && obstacle != null)
{
// Edge case: last point is exit point. We still have an active obstacle instance
// If obstacle entry is curPoint, this is the same point and this is not an obstacle
if (!obstacle.EntryPoint.Equals(curPoint))
{
obstacle.ExitPoint = curPoint;
metrics.AddObstacle(obstacle);
obstacle = null;
}
}
#endregion
lastElevation = currentElevation;
}
metrics.Climb = totalClimb;
metrics.Descent = totalDescent;
metrics.NumPoints = points.Count;
metrics.Distance = total;
metrics.MinElevation = minElevation;
metrics.MaxElevation = maxElevation;
metrics.HasVoids = numNoDataPoints > 0;
metrics.NumVoidPoints = numNoDataPoints;
return(metrics);
}
internal void AddObstacle(IntervisibilityObstacle obstacle)
{
Obstacles.Add(obstacle);
}