mirror of
https://github.com/bilawalsidhu/gods-eye-view.git
synced 2026-11-05 10:53:59 +00:00
69 lines
2.0 KiB
JavaScript
69 lines
2.0 KiB
JavaScript
/**
|
|
* Resample a GRIB wind grid into a compact equirectangular grid.
|
|
*
|
|
* Source grids are north-to-south (`la1` at the top, `dj` increasing toward the
|
|
* south) and start at `lo1`. Longitude wraps across the seam; latitude clamps.
|
|
*
|
|
* @param {{u: ArrayLike<number>, v: ArrayLike<number>, ni: number, nj: number,
|
|
* lo1: number, la1: number, di: number, dj: number, dx?: number, dy?: number}} input
|
|
* @returns {{nx: number, ny: number, lo1: number, la1: number, dx: number,
|
|
* dy: number, u: Float32Array, v: Float32Array}}
|
|
*/
|
|
export function resampleWindGrid({
|
|
u,
|
|
v,
|
|
ni,
|
|
nj,
|
|
lo1,
|
|
la1,
|
|
di,
|
|
dj,
|
|
dx = 1,
|
|
dy = 1,
|
|
}) {
|
|
if (
|
|
!Number.isInteger(ni) ||
|
|
!Number.isInteger(nj) ||
|
|
ni < 1 ||
|
|
nj < 1 ||
|
|
ni * nj > 2_000_000 ||
|
|
u?.length !== ni * nj ||
|
|
v?.length !== ni * nj ||
|
|
![lo1, la1, di, dj, dx, dy].every(Number.isFinite) ||
|
|
di <= 0 ||
|
|
dj <= 0 ||
|
|
dx < 0.25 ||
|
|
dy < 0.25 ||
|
|
dx > 180 ||
|
|
dy > 180
|
|
)
|
|
throw new Error('Invalid wind grid geometry');
|
|
const nx = Math.round(360 / dx);
|
|
const ny = Math.round(180 / dy) + 1;
|
|
const outU = new Float32Array(nx * ny);
|
|
const outV = new Float32Array(nx * ny);
|
|
const sample = (source, lon, lat) => {
|
|
const x = ((lon - lo1) / di + ni) % ni;
|
|
const y = Math.max(0, Math.min(nj - 1, (la1 - lat) / dj));
|
|
const x0 = Math.floor(x);
|
|
const x1 = (x0 + 1) % ni;
|
|
const y0 = Math.floor(y);
|
|
const y1 = Math.min(nj - 1, y0 + 1);
|
|
const fx = x - x0;
|
|
const fy = y - y0;
|
|
const top = source[y0 * ni + x0] * (1 - fx) + source[y0 * ni + x1] * fx;
|
|
const bottom = source[y1 * ni + x0] * (1 - fx) + source[y1 * ni + x1] * fx;
|
|
return top * (1 - fy) + bottom * fy;
|
|
};
|
|
for (let y = 0; y < ny; y += 1) {
|
|
for (let x = 0; x < nx; x += 1) {
|
|
const index = y * nx + x;
|
|
const lon = x * dx;
|
|
const lat = 90 - y * dy;
|
|
outU[index] = sample(u, lon, lat);
|
|
outV[index] = sample(v, lon, lat);
|
|
}
|
|
}
|
|
return { nx, ny, lo1: 0, la1: 90, dx, dy, u: outU, v: outV };
|
|
}
|