gridtracker/package.nw/lib/arc.js

353 wiersze
8.7 KiB
JavaScript

"use strict";
var D2R = Math.PI / 180;
var R2D = 180 / Math.PI;
var Coord = function (lon, lat)
{
this.lon = lon;
this.lat = lat;
this.x = D2R * lon;
this.y = D2R * lat;
};
Coord.prototype.view = function ()
{
return String(this.lon).slice(0, 4) + "," + String(this.lat).slice(0, 4);
};
Coord.prototype.antipode = function ()
{
var anti_lat = -1 * this.lat;
var anti_lon = this.lon < 0 ? 180 + this.lon : (180 - this.lon) * -1;
return new Coord(anti_lon, anti_lat);
};
var LineString = function ()
{
this.coords = [];
this.length = 0;
};
LineString.prototype.move_to = function (coord)
{
this.length++;
this.coords.push(coord);
};
var Arc = function (properties)
{
this.properties = properties || {};
this.geometries = [];
};
Arc.prototype.json = function ()
{
if (this.geometries.length <= 0)
{
return {
geometry: { type: "LineString", coordinates: null },
type: "Feature",
properties: this.properties
};
}
else if (this.geometries.length == 1)
{
return {
geometry: { type: "LineString", coordinates: this.geometries[0].coords },
type: "Feature",
properties: this.properties
};
}
else
{
var multiline = [];
for (var i = 0; i < this.geometries.length; i++)
{
multiline.push(this.geometries[i].coords);
}
return {
geometry: { type: "MultiLineString", coordinates: multiline },
type: "Feature",
properties: this.properties
};
}
};
// TODO - output proper multilinestring
Arc.prototype.wkt = function ()
{
var wkt_string = "";
var wkt = "LINESTRING(";
var collect = function (c)
{
wkt += c[0] + " " + c[1] + ",";
};
for (var i = 0; i < this.geometries.length; i++)
{
if (this.geometries[i].coords.length === 0)
{
return "LINESTRING(empty)";
}
else
{
var coords = this.geometries[i].coords;
coords.forEach(collect);
wkt_string += wkt.substring(0, wkt.length - 1) + ")";
}
}
return wkt_string;
};
/*
* http://en.wikipedia.org/wiki/Great-circle_distance
*
*/
var GreatCircle = function (start, end, properties)
{
if (!start || start.x === undefined || start.y === undefined)
{
throw new Error(
"GreatCircle constructor expects two args: start and end objects with x and y properties"
);
}
if (!end || end.x === undefined || end.y === undefined)
{
throw new Error(
"GreatCircle constructor expects two args: start and end objects with x and y properties"
);
}
this.start = new Coord(start.x, start.y);
this.end = new Coord(end.x, end.y);
this.properties = properties || {};
var w = this.start.x - this.end.x;
var h = this.start.y - this.end.y;
var z =
Math.pow(Math.sin(h / 2.0), 2) +
Math.cos(this.start.y) *
Math.cos(this.end.y) *
Math.pow(Math.sin(w / 2.0), 2);
this.g = 2.0 * Math.asin(Math.sqrt(z));
if (this.g == Math.PI)
{
throw new Error(
"it appears " +
start.view() +
" and " +
end.view() +
" are 'antipodal', e.g diametrically opposite, thus there is no single route but rather infinite"
);
}
else if (isNaN(this.g))
{
throw new Error(
"could not calculate great circle between " + start + " and " + end
);
}
};
/*
* http://williams.best.vwh.net/avform.htm#Intermediate
*/
GreatCircle.prototype.interpolate = function (f)
{
var A = Math.sin((1 - f) * this.g) / Math.sin(this.g);
var B = Math.sin(f * this.g) / Math.sin(this.g);
var x =
A * Math.cos(this.start.y) * Math.cos(this.start.x) +
B * Math.cos(this.end.y) * Math.cos(this.end.x);
var y =
A * Math.cos(this.start.y) * Math.sin(this.start.x) +
B * Math.cos(this.end.y) * Math.sin(this.end.x);
var z = A * Math.sin(this.start.y) + B * Math.sin(this.end.y);
var lat = R2D * Math.atan2(z, Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)));
var lon = R2D * Math.atan2(y, x);
return [lon, lat];
};
/*
* Generate points along the great circle
*/
GreatCircle.prototype.Arc = function (npoints, options)
{
var first_pass = [];
if (!npoints || npoints <= 2)
{
first_pass.push([this.start.lon, this.start.lat]);
first_pass.push([this.end.lon, this.end.lat]);
}
else
{
var delta = 1.0 / (npoints - 1);
for (var i = 0; i < npoints; ++i)
{
var step = delta * i;
var pair = this.interpolate(step);
first_pass.push(pair);
}
}
/* partial port of dateline handling from:
gdal/ogr/ogrgeometryfactory.cpp
TODO - does not handle all wrapping scenarios yet
*/
var bHasBigDiff = false;
var dfMaxSmallDiffLong = 0;
// from http://www.gdal.org/ogr2ogr.html
// -datelineoffset:
// (starting with GDAL 1.10) offset from dateline in degrees (default long. = +/- 10deg, geometries within 170deg to -170deg will be splited)
var dfDateLineOffset = options && options.offset ? options.offset : 10;
var dfLeftBorderX = 180 - dfDateLineOffset;
var dfRightBorderX = -180 + dfDateLineOffset;
var dfDiffSpace = 360 - dfDateLineOffset;
// https://github.com/OSGeo/gdal/blob/7bfb9c452a59aac958bff0c8386b891edf8154ca/gdal/ogr/ogrgeometryfactory.cpp#L2342
for (var j = 1; j < first_pass.length; ++j)
{
var dfPrevX = first_pass[j - 1][0];
var dfX = first_pass[j][0];
var dfDiffLong = Math.abs(dfX - dfPrevX);
if (
dfDiffLong > dfDiffSpace &&
((dfX > dfLeftBorderX && dfPrevX < dfRightBorderX) ||
(dfPrevX > dfLeftBorderX && dfX < dfRightBorderX))
)
{
bHasBigDiff = true;
}
else if (dfDiffLong > dfMaxSmallDiffLong)
{
dfMaxSmallDiffLong = dfDiffLong;
}
}
var poMulti = [];
if (bHasBigDiff && dfMaxSmallDiffLong < dfDateLineOffset)
{
var poNewLS = [];
poMulti.push(poNewLS);
for (var k = 0; k < first_pass.length; ++k)
{
var dfX0 = parseFloat(first_pass[k][0]);
if (k > 0 && Math.abs(dfX0 - first_pass[k - 1][0]) > dfDiffSpace)
{
var dfX1 = parseFloat(first_pass[k - 1][0]);
var dfY1 = parseFloat(first_pass[k - 1][1]);
var dfX2 = parseFloat(first_pass[k][0]);
var dfY2 = parseFloat(first_pass[k][1]);
if (
dfX1 > -180 &&
dfX1 < dfRightBorderX &&
dfX2 == 180 &&
k + 1 < first_pass.length &&
first_pass[k - 1][0] > -180 &&
first_pass[k - 1][0] < dfRightBorderX
)
{
poNewLS.push([-180, first_pass[k][1]]);
k++;
poNewLS.push([first_pass[k][0], first_pass[k][1]]);
continue;
}
else if (
dfX1 > dfLeftBorderX &&
dfX1 < 180 &&
dfX2 == -180 &&
k + 1 < first_pass.length &&
first_pass[k - 1][0] > dfLeftBorderX &&
first_pass[k - 1][0] < 180
)
{
poNewLS.push([180, first_pass[k][1]]);
k++;
poNewLS.push([first_pass[k][0], first_pass[k][1]]);
continue;
}
if (dfX1 < dfRightBorderX && dfX2 > dfLeftBorderX)
{
// swap dfX1, dfX2
var tmpX = dfX1;
dfX1 = dfX2;
dfX2 = tmpX;
// swap dfY1, dfY2
var tmpY = dfY1;
dfY1 = dfY2;
dfY2 = tmpY;
}
if (dfX1 > dfLeftBorderX && dfX2 < dfRightBorderX)
{
dfX2 += 360;
}
if (dfX1 <= 180 && dfX2 >= 180 && dfX1 < dfX2)
{
var dfRatio = (180 - dfX1) / (dfX2 - dfX1);
var dfY = dfRatio * dfY2 + (1 - dfRatio) * dfY1;
poNewLS.push([
first_pass[k - 1][0] > dfLeftBorderX ? 180 : -180,
dfY
]);
poNewLS = [];
poNewLS.push([
first_pass[k - 1][0] > dfLeftBorderX ? -180 : 180,
dfY
]);
poMulti.push(poNewLS);
}
else
{
poNewLS = [];
poMulti.push(poNewLS);
}
poNewLS.push([dfX0, first_pass[k][1]]);
}
else
{
poNewLS.push([first_pass[k][0], first_pass[k][1]]);
}
}
}
else
{
// add normally
var poNewLS0 = [];
poMulti.push(poNewLS0);
for (var l = 0; l < first_pass.length; ++l)
{
poNewLS0.push([first_pass[l][0], first_pass[l][1]]);
}
}
var arc = new Arc(this.properties);
for (var m = 0; m < poMulti.length; ++m)
{
var line = new LineString();
arc.geometries.push(line);
var points = poMulti[m];
for (var j0 = 0; j0 < points.length; ++j0)
{
line.move_to(points[j0]);
}
}
return arc;
};
if (typeof module !== "undefined" && typeof module.exports !== "undefined")
{
// nodejs
module.exports.Coord = Coord;
module.exports.Arc = Arc;
module.exports.GreatCircle = GreatCircle;
}
else
{
// browser
var arc = {};
arc.Coord = Coord;
arc.Arc = Arc;
arc.GreatCircle = GreatCircle;
}