/// <summary>
/// Returns the NW, NE, SW, SE corners of the township
/// </summary>
/// <param name="township"></param>
/// <param name="range"></param>
/// <param name="meridian"></param>
/// <returns></returns>
internal LatLongCorners[] TownshipMarkers(byte township, byte range, byte meridian)
{
//ask the boundary provider for a list of sections that border this township
//each township is numbered as:
// 31|32|33|34|35|36
// 30|29|28|27|26|25
// 19|20|21|22|23|24
// 18|17|16|15|14|13
// 07|08|09|10|11|12
// 06|05|04|03|02|01
//look at each coordinate pair until we find ones that are the extreme corners
var key = (ushort)(meridian << 13 | range << 7 | township);
if (!_offsets.TryGetValue(key, out var townshipFloats))
{
return(null);
}
int section = 0;
var corners = new LatLongCorners[36];
for (int offset = 0; offset < 288; offset += 8)
{
var se = LatLongCoordinate(townshipFloats, offset + 0);
var sw = LatLongCoordinate(townshipFloats, offset + 2);
var nw = LatLongCoordinate(townshipFloats, offset + 4);
var ne = LatLongCoordinate(townshipFloats, offset + 6);
// Build a boundary object that contains 1-4 corners.
corners[section] = new LatLongCorners(se, sw, nw, ne);
section++;
}
return(corners);
}
private static LatLongCoordinate Interpolate4Point(byte legalSubdivision, LatLongCorners geoList)
{
if (geoList.SouthEast == null || geoList.SouthWest == null || geoList.NorthWest == null || geoList.NorthEast == null)
{
return(LatLongCoordinate.Origin);
}
var lat = new float[2, 2];
var lng = new float[2, 2];
lat[0, 0] = geoList.SouthWest.Value.Latitude;
lat[0, 1] = geoList.SouthEast.Value.Latitude;
lat[1, 0] = geoList.NorthWest.Value.Latitude;
lat[1, 1] = geoList.NorthEast.Value.Latitude;
lng[0, 0] = geoList.SouthWest.Value.Longitude;
lng[0, 1] = geoList.SouthEast.Value.Longitude;
lng[1, 0] = geoList.NorthWest.Value.Longitude;
lng[1, 1] = geoList.NorthEast.Value.Longitude;
return(BilinearInterpolate(legalSubdivision, lat, lng));
}