/// <summary>
/// Lookup the coordinate and compare it against all known section markers,
/// returns the best fit section
/// </summary>
/// <param name="coordinate"></param>
/// <returns></returns>
public static DlsSystem?FromLatLongCoordinate(LatLongCoordinate coordinate)
{
// This method estimates a township that is close to the coordinate.
if (!TryInferTownshipForLatLongCoordinate(coordinate, out byte meridian, out byte range, out byte township))
{
return(null);
}
//get all markers in township
var markers = DlsSurveyCoordinateProvider.Instance.TownshipMarkers(township, range, meridian);
if (markers == null)
{
return(null);
}
//each township is numbered as: there are a max of 4 markers per section with 2 floats = 144 coordinates
// some markers are empty (that section does not exist)
// 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
double bestDistance = double.MaxValue;
DlsSystem?bestDls = null;
//test each section in the town
for (byte section = 1; section <= 36; section++)
{
var dlsBoundary = markers[section - 1];
if (dlsBoundary == null || dlsBoundary.Count == 0)
{
continue; //invalid section
}
//find the center for each lsd in the section
for (byte legalSubdivision = 1; legalSubdivision <= 16; legalSubdivision++)
{
double testDistance;
switch (dlsBoundary.Count)
{
case 4:
testDistance = coordinate.RelativeDistanceTo(Interpolate4Point(legalSubdivision, dlsBoundary));
break;
default:
testDistance = double.MaxValue; //should never get here
break;
}
if (testDistance < bestDistance)
{
bestDistance = testDistance;
bestDls = new DlsSystem(legalSubdivision, section, township, range, meridian);
}
}
}
return(bestDls);
}
/// <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>
public LatLongCorners TownshipBoundary(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);
}
LatLongCoordinate?se = null, sw = null, ne = null, nw = null;
int c = 0;
for (int i = 0; i < 144; i++)
{
var lat = townshipFloats[c++];
var lon = townshipFloats[c++];
if (lat == 0 && lon == 0)
{
continue;
}
if (se == null || lat < se.Value.Latitude && lon > se.Value.Longitude)
{
se = new LatLongCoordinate(lat, lon);
}
if (sw == null || lat < sw.Value.Latitude && lon < sw.Value.Longitude)
{
sw = new LatLongCoordinate(lat, lon);
}
if (ne == null || lat > ne.Value.Latitude && lon > ne.Value.Longitude)
{
ne = new LatLongCoordinate(lat, lon);
}
if (nw == null || lat > nw.Value.Latitude && lon < nw.Value.Longitude)
{
nw = new LatLongCoordinate(lat, lon);
}
}
return(new LatLongCorners(se, sw, nw, ne));
}
/// <summary>
/// Makes a best guess at the Township that contains the given coordinate.
/// </summary>
/// <param name="coordinate">The lat long to use when looking up a township</param>
/// <param name="meridian"></param>
/// <param name="range"></param>
/// <param name="township"></param>
/// <returns></returns>
private static bool TryInferTownshipForLatLongCoordinate(LatLongCoordinate coordinate, out byte meridian, out byte range, out byte township)
{
meridian = 0;
range = 0;
township = 0;
var longitude = coordinate.Longitude;
if (longitude > Meridians[0] || longitude < Meridians[Meridians.Length - 1])
{
throw new CoordinateConversionException("Meridian is out of range");
}
//determine the base meridian
byte mrd = 0;
for (byte k = 1; k < 8; k++)
{
if (longitude <= Meridians[k - 1] && longitude > Meridians[k])
{
mrd = k;
break;
}
}
if (mrd == 0)
{
return(false);
}
var twp = (byte)(Math.Floor((coordinate.Latitude - BaseLatitude) / TownshipHeightInDegrees) + 1);
if (twp <= 0)
{
return(false);
}
double townshipWidthInDegrees = 6 * GetSectionWidthInDegrees(twp);
double meridianLongitude = Meridians[mrd - 1];
//subtract the meridian from the longitude and use the remainder to calculate the range number
var rng = (byte)(Math.Floor((longitude - meridianLongitude) / townshipWidthInDegrees) + 1);
meridian = mrd;
range = rng;
township = twp;
return(true);
}
private static LatLongCoordinate?LatLongCoordinate(float[] townshipFloats, int offset)
{
var lat = townshipFloats[offset];
var lon = townshipFloats[offset + 1];
LatLongCoordinate?coordinate;
if (lat == 0 && lon == 0)
{
coordinate = null;
}
else
{
coordinate = new LatLongCoordinate(lat, lon);
}
return(coordinate);
}
/// <summary>
/// Converts the <see cref="LatLongCoordinate"/> instance to a BC NTS location.
/// </summary>
/// <param name="coordinate">The coordinate.</param>
/// <returns></returns>
public static BcNtsGridSystem FromLatLongCoordinates(LatLongCoordinate coordinate)
{
var longitude = Math.Abs(coordinate.Longitude);
var latitude = Math.Abs(coordinate.Latitude);
byte pq = 0;
foreach (var keyValuePair in LatPq)
{
var q = keyValuePair.Key;
if (latitude >= LatPq[q] && latitude < LatPq[q] + 4 &&
longitude >= LngPq[q] && longitude < LngPq[q] + 8)
{
pq = q;
break;
}
}
if (pq == 0)
{
throw new CoordinateConversionException("The geographic location is not in a BC primary quadrant.");
}
var lat = latitude - LatPq[pq];
var lng = longitude - LngPq[pq];
var lq = '\0';
foreach (var key in LatLq.Keys)
{
if (lat >= LatLq[key] && lat < LatLq[key] + 1 &&
lng >= LngLq[key] && lng < LngLq[key] + 2)
{
lq = key;
break;
}
}
if (lq == '\0')
{
throw new CoordinateConversionException("lq is invalid.");
}
lat -= LatLq[lq];
lng -= LngLq[lq];
byte six = 0;
foreach (var n in LatSix.Keys)
{
if (lat >= LatSix[n] && lat < LatSix[n] + 0.25 &&
lng >= LngSix[n] && lng < LngSix[n] + 0.5)
{
six = n;
break;
}
}
if (six == 0)
{
throw new CoordinateConversionException("six is invalid");
}
lat -= LatSix[six];
lng -= LngSix[six];
var zn = '\0';
foreach (var n in LatZn.Keys)
{
if (lat >= LatZn[n] && lat < LatZn[n] + BlockHeight &&
lng >= LngZn[n] && lng < LngZn[n] + BlockWidth)
{
zn = n;
break;
}
}
if (zn == '\0')
{
throw new CoordinateConversionException("Zone is invalid");
}
lat -= LatZn[zn];
lng -= LngZn[zn];
//every unit is 1/120 high by 1/80 wide
var y = (byte)Math.Floor(120 * lat);
var x = (byte)Math.Floor(lng / 0.0125);
var unit = (byte)(x + 1 + y * 10);
lat -= y / 120.0;
lng -= x * 0.0125;
var qtr = '\0';
foreach (var n in LatQtr.Keys)
{
if (lat >= LatQtr[n] && lat < LatQtr[n] + QuarterUnitHeight &&
lng >= LngQtr[n] && lng < LngQtr[n] + QuarterUnitWidth)
{
qtr = n;
break;
}
}
if (qtr == '\0')
{
throw new CoordinateConversionException("Quarter is invalid.");
}
return(new BcNtsGridSystem(qtr, unit, zn, pq, lq, six));
}
