s2-geometry.js/src/s2geometry.js

/// S2 Geometry functions
// the regional scoreboard is based on a level 6 S2 Cell
// - https://docs.google.com/presentation/d/1Hl4KapfAENAOf4gv-pSngKwvS_jwNVHRPZTTDzXXn6Q/view?pli=1#slide=id.i22
// at the time of writing there's no actual API for the intel map to retrieve scoreboard data,
// but it's still useful to plot the score cells on the intel map


// the S2 geometry is based on projecting the earth sphere onto a cube, with some scaling of face coordinates to
// keep things close to approximate equal area for adjacent cells
// to convert a lat,lng into a cell id:
// - convert lat,lng to x,y,z
// - convert x,y,z into face,u,v
// - u,v scaled to s,t with quadratic formula
// - s,t converted to integer i,j offsets
// - i,j converted to a position along a Hubbert space-filling curve
// - combine face,position to get the cell id

//NOTE: compared to the google S2 geometry library, we vary from their code in the following ways
// - cell IDs: they combine face and the hilbert curve position into a single 64 bit number. this gives efficient space
//             and speed. javascript doesn't have appropriate data types, and speed is not cricical, so we use
//             as [face,[bitpair,bitpair,...]] instead
// - i,j: they always use 30 bits, adjusting as needed. we use 0 to (1<<level)-1 instead
//        (so GetSizeIJ for a cell is always 1)

(function() {
'use strict';

window.S2 = {};

var LatLngToXYZ = function(latLng) {
  var d2r = L.LatLng.DEG_TO_RAD;

  var phi = latLng.lat*d2r;
  var theta = latLng.lng*d2r;

  var cosphi = Math.cos(phi);

  return [Math.cos(theta)*cosphi, Math.sin(theta)*cosphi, Math.sin(phi)];
};

var XYZToLatLng = function(xyz) {
  var r2d = L.LatLng.RAD_TO_DEG;

  var lat = Math.atan2(xyz[2], Math.sqrt(xyz[0]*xyz[0]+xyz[1]*xyz[1]));
  var lng = Math.atan2(xyz[1], xyz[0]);

  return L.LatLng(lat*r2d, lng*r2d);
};

var largestAbsComponent = function(xyz) {
  var temp = [Math.abs(xyz[0]), Math.abs(xyz[1]), Math.abs(xyz[2])];

  if (temp[0] > temp[1]) {
    if (temp[0] > temp[2]) {
      return 0;
    } else {
      return 2;
    }
  } else {
    if (temp[1] > temp[2]) {
      return 1;
    } else {
      return 2;
    }
  }

};

var faceXYZToUV = function(face,xyz) {
  var u,v;

  switch (face) {
    case 0: u =  xyz[1]/xyz[0]; v =  xyz[2]/xyz[0]; break;
    case 1: u = -xyz[0]/xyz[1]; v =  xyz[2]/xyz[1]; break;
    case 2: u = -xyz[0]/xyz[2]; v = -xyz[1]/xyz[2]; break;
    case 3: u =  xyz[2]/xyz[0]; v =  xyz[1]/xyz[0]; break;
    case 4: u =  xyz[2]/xyz[1]; v = -xyz[0]/xyz[1]; break;
    case 5: u = -xyz[1]/xyz[2]; v = -xyz[0]/xyz[2]; break;
    default: throw {error: 'Invalid face'}; break;
  }

  return [u,v];
}




var XYZToFaceUV = function(xyz) {
  var face = largestAbsComponent(xyz);

  if (xyz[face] < 0) {
    face += 3;
  }

  uv = faceXYZToUV (face,xyz);

  return [face, uv];
};

var FaceUVToXYZ = function(face,uv) {
  var u = uv[0];
  var v = uv[1];

  switch (face) {
    case 0: return [ 1, u, v];
    case 1: return [-u, 1, v];
    case 2: return [-u,-v, 1];
    case 3: return [-1,-v,-u];
    case 4: return [ v,-1,-u];
    case 5: return [ v, u,-1];
    default: throw {error: 'Invalid face'};
  }
};


var STToUV = function(st) {
  var singleSTtoUV = function(st) {
    if (st >= 0.5) {
      return (1/3.0) * (4*st*st - 1);
    } else {
      return (1/3.0) * (1 - (4*(1-st)*(1-st)));
    }
  }

  return [singleSTtoUV(st[0]), singleSTtoUV(st[1])];
};



var UVToST = function(uv) {
  var singleUVtoST = function(uv) {
    if (uv >= 0) {
      return 0.5 * Math.sqrt (1 + 3*uv);
    } else {
      return 1 - 0.5 * Math.sqrt (1 - 3*uv);
    }
  }

  return [singleUVtoST(uv[0]), singleUVtoST(uv[1])];
};


var STToIJ = function(st,order) {
  var maxSize = (1<<order);

  var singleSTtoIJ = function(st) {
    var ij = Math.floor(st * maxSize);
    return Math.max(0, Math.min(maxSize-1, ij));
  };

  return [singleSTtoIJ(st[0]), singleSTtoIJ(st[1])];
};


var IJToST = function(ij,order,offsets) {
  var maxSize = (1<<order);

  return [
    (ij[0]+offsets[0])/maxSize,
    (ij[1]+offsets[1])/maxSize
  ];
}

// hilbert space-filling curve
// based on http://blog.notdot.net/2009/11/Damn-Cool-Algorithms-Spatial-indexing-with-Quadtrees-and-Hilbert-Curves
// note: rather then calculating the final integer hilbert position, we just return the list of quads
// this ensures no precision issues whth large orders (S3 cell IDs use up to 30), and is more
// convenient for pulling out the individual bits as needed later
var pointToHilbertQuadList = function(x,y,order) {
  var hilbertMap = {
    'a': [ [0,'d'], [1,'a'], [3,'b'], [2,'a'] ],
    'b': [ [2,'b'], [1,'b'], [3,'a'], [0,'c'] ],
    'c': [ [2,'c'], [3,'d'], [1,'c'], [0,'b'] ],
    'd': [ [0,'a'], [3,'c'], [1,'d'], [2,'d'] ]  
  };

  var currentSquare='a';
  var positions = [];

  for (var i=order-1; i>=0; i--) {

    var mask = 1<<i;

    var quad_x = x&mask ? 1 : 0;
    var quad_y = y&mask ? 1 : 0;

    var t = hilbertMap[currentSquare][quad_x*2+quad_y];

    positions.push(t[0]);

    currentSquare = t[1];
  }

  return positions;
};




// S2Cell class

S2.S2Cell = function(){};

//static method to construct
S2.S2Cell.FromLatLng = function(latLng,level) {

  var xyz = LatLngToXYZ(latLng);

  var faceuv = XYZToFaceUV(xyz);
  var st = UVToST(faceuv[1]);

  var ij = STToIJ(st,level);

  return S2.S2Cell.FromFaceIJ (faceuv[0], ij, level);

  return result;
};

S2.S2Cell.FromFaceIJ = function(face,ij,level) {
  var cell = new S2.S2Cell();
  cell.face = face;
  cell.ij = ij;
  cell.level = level;

  return cell;
};


S2.S2Cell.prototype.toString = function() {
  return 'F'+this.face+'ij['+this.ij[0]+','+this.ij[1]+']@'+this.level;
};

S2.S2Cell.prototype.getLatLng = function() {
  var st = IJToST(this.ij,this.level, [0.5,0.5]);
  var uv = STToUV(st);
  var xyz = FaceUVToXYZ(this.face, uv);

  return XYZToLatLng(xyz);  
};

S2.S2Cell.prototype.getCornerLatLngs = function() {
  var result = [];
  var offsets = [
    [ 0.0, 0.0 ],
    [ 0.0, 1.0 ],
    [ 1.0, 1.0 ],
    [ 1.0, 0.0 ]
  ];

  for (var i=0; i<4; i++) {
    var st = IJToST(this.ij, this.level, offsets[i]);
    var uv = STToUV(st);
    var xyz = FaceUVToXYZ(this.face, uv);

    result.push ( XYZToLatLng(xyz) );
  }
  return result;
};


S2.S2Cell.prototype.getFaceAndQuads = function() {
  var quads = pointToHilbertQuadList(this.ij[0], this.ij[1], this.level);

  return [this.face,quads];
};

S2.S2Cell.prototype.getNeighbors = function() {

  var fromFaceIJWrap = function(face,ij,level) {
    var maxSize = (1<<level);
    if (ij[0]>=0 && ij[1]>=0 && ij[0]<maxSize && ij[1]<maxSize) {
      // no wrapping out of bounds
      return S2.S2Cell.FromFaceIJ(face,ij,level);
    } else {
      // the new i,j are out of range.
      // with the assumption that they're only a little past the borders we can just take the points as
      // just beyond the cube face, project to XYZ, then re-create FaceUV from the XYZ vector

      var st = IJToST(ij,level,[0.5,0.5]);
      var uv = STToUV(st);
      var xyz = FaceUVToXYZ(face,uv);
      var faceuv = XYZToFaceUV(xyz);
      face = faceuv[0];
      uv = faceuv[1];
      st = UVToST(uv);
      ij = STToIJ(st,level);
      return S2.S2Cell.FromFaceIJ (face, ij, level);
    }
  };

  var face = this.face;
  var i = this.ij[0];
  var j = this.ij[1];
  var level = this.level;


  return [
    fromFaceIJWrap(face, [i-1,j], level),
    fromFaceIJWrap(face, [i,j-1], level),
    fromFaceIJWrap(face, [i+1,j], level),
    fromFaceIJWrap(face, [i,j+1], level)
  ];

};


})();

(function () {
'use strict';

  // Adapted from Leafletjs https://searchcode.com/codesearch/view/42525008/

  var L = { LatLng: {} };
  windows.L = L;

  L.LatLng.DEG_TO_RAD = Math.PI / 180;
  L.LatLng.RAD_TO_DEG = 180 / Math.PI;

  L.LatLng = function (/*Number*/ rawLat, /*Number*/ rawLng, /*Boolean*/ noWrap) {
    var lat = parseFloat(rawLat);
    var lng = parseFloat(rawLng);

    if (isNaN(lat) || isNaN(lng)) {
      throw new Error('Invalid LatLng object: (' + rawLat + ', ' + rawLng + ')');
    }

    if (noWrap !== true) {
      lat = Math.max(Math.min(lat, 90), -90);                 // clamp latitude into -90..90
      lng = (lng + 180) % 360 + ((lng < -180 || lng === 180) ? 180 : -180);   // wrap longtitude into -180..180
    }

    return { lat: lat, lng: lng };
  };
})();