mirror of
https://github.com/mauriceboe/TREK.git
synced 2026-10-22 06:56:35 +00:00
Maurice
beea4c762b
The binary heap and the flat-frame distance helpers are not about water; the piste router needs the same two. They move to src/lib/geo, where any domain may import them without reaching into paddle-routing. Nothing changes in what they do.
72 lines
2.0 KiB
TypeScript
72 lines
2.0 KiB
TypeScript
/** Metres per degree of latitude, the figure the routing code reckons with throughout. */
|
|
const M_PER_DEG = 111_195;
|
|
|
|
export function metresBetween(aLat: number, aLng: number, bLat: number, bLng: number): number {
|
|
const cos = Math.cos((((aLat + bLat) / 2) * Math.PI) / 180);
|
|
return Math.hypot((bLat - aLat) * M_PER_DEG, (bLng - aLng) * M_PER_DEG * cos);
|
|
}
|
|
|
|
/**
|
|
* A flat frame in metres around one spot, good for the few kilometres a lake
|
|
* or a stretch of river spans: x east, y north.
|
|
*/
|
|
export class LocalFrame {
|
|
readonly cos: number;
|
|
|
|
constructor(
|
|
readonly lat0: number,
|
|
readonly lng0: number,
|
|
) {
|
|
this.cos = Math.cos((lat0 * Math.PI) / 180);
|
|
}
|
|
|
|
x(lng: number): number {
|
|
return (lng - this.lng0) * M_PER_DEG * this.cos;
|
|
}
|
|
|
|
y(lat: number): number {
|
|
return (lat - this.lat0) * M_PER_DEG;
|
|
}
|
|
|
|
lat(y: number): number {
|
|
return this.lat0 + y / M_PER_DEG;
|
|
}
|
|
|
|
lng(x: number): number {
|
|
return this.lng0 + x / (M_PER_DEG * this.cos);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Where a point falls on a segment: the share along it (clamped to the
|
|
* segment) and the distance to it, in metres.
|
|
*/
|
|
export function projectOnSegment(
|
|
lat: number,
|
|
lng: number,
|
|
aLat: number,
|
|
aLng: number,
|
|
bLat: number,
|
|
bLng: number,
|
|
): { t: number; distance: number } {
|
|
const cos = Math.cos((lat * Math.PI) / 180);
|
|
const ax = (aLng - lng) * cos;
|
|
const ay = aLat - lat;
|
|
const dx = (bLng - aLng) * cos;
|
|
const dy = bLat - aLat;
|
|
const length2 = dx * dx + dy * dy;
|
|
const t = length2 === 0 ? 0 : Math.max(0, Math.min(1, -(ax * dx + ay * dy) / length2));
|
|
return { t, distance: Math.hypot(ax + t * dx, ay + t * dy) * M_PER_DEG };
|
|
}
|
|
|
|
/** The length of a [lat, lng] line in metres. */
|
|
export function lineLength(points: ReadonlyArray<readonly [number, number]>): number {
|
|
let total = 0;
|
|
for (let i = 1; i < points.length; i++) {
|
|
const a = points[i - 1] as readonly [number, number];
|
|
const b = points[i] as readonly [number, number];
|
|
total += metresBetween(a[0], a[1], b[0], b[1]);
|
|
}
|
|
return total;
|
|
}
|