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internal/pkg/grib/extractor.go

@@ -4,30 +4,100 @@ import "math"
 
 func lerp(a, b, t float64) float64 { return a + t*(b-a) }
 
-// Interpolate 16‑point (time, p, lat, lon)
+// ghInterp returns interpolated geopotential height at given time/pressure/lat/lon
+func (d *dataset) ghInterp(ti, pi int, y0, y1, x0, x1 int, wy, wx float64) float64 {
+	g00 := d.cube.val(0, ti, pi, y0, x0)
+	g10 := d.cube.val(0, ti, pi, y0, x1)
+	g01 := d.cube.val(0, ti, pi, y1, x0)
+	g11 := d.cube.val(0, ti, pi, y1, x1)
+	return (1-wy)*((1-wx)*float64(g00)+wx*float64(g10)) + wy*((1-wx)*float64(g01)+wx*float64(g11))
+}
+
+// searchAltLevel uses geopotential height to find pressure level bracket for target altitude.
+func (d *dataset) searchAltLevel(alt float64, ti, y0, y1, x0, x1 int, wy, wx float64) (int, float64) {
+	levels := d.ds.Levels
+	nLevels := len(levels)
+
+	lo, hi := 0, nLevels-1
+	for lo < hi-1 {
+		mid := (lo + hi) / 2
+		ghMid := d.ghInterp(ti, mid, y0, y1, x0, x1, wy, wx)
+		if ghMid < alt {
+			lo = mid
+		} else {
+			hi = mid
+		}
+	}
+
+	ghLo := d.ghInterp(ti, lo, y0, y1, x0, x1, wy, wx)
+	ghHi := d.ghInterp(ti, hi, y0, y1, x0, x1, wy, wx)
+
+	wp := 0.0
+	if ghHi != ghLo {
+		wp = (alt - ghLo) / (ghHi - ghLo)
+	}
+	if wp < 0 {
+		wp = 0
+	}
+	if wp > 1 {
+		wp = 1
+	}
+
+	return lo, wp
+}
+
+// uv выполняет интерполяцию ветра по 4 измерениям (time, pressure, lat, lon).
 func (d *dataset) uv(lat, lon, alt float64, tHours float64) (float64, float64) {
 	if lon < 0 {
 		lon += 360
 	}
-	iy := (lat + 90) * 2
+
+	inv := d.ds.InvResolution()
+
+	// GRIB scan north→south: index 0 = 90°N
+	iy := (90 - lat) * inv
 	y0 := int(math.Floor(iy))
+	if y0 < 0 {
+		y0 = 0
+	}
+	if y0 >= d.cube.lat-1 {
+		y0 = d.cube.lat - 2
+	}
 	y1 := y0 + 1
 	wy := iy - float64(y0)
-	ix := lon * 2
+
+	ix := lon * inv
 	x0 := int(math.Floor(ix)) % d.cube.lon
 	x1 := (x0 + 1) % d.cube.lon
 	wx := ix - float64(x0)
-	// For 3-hourly data (step = 3 hours)
-	// Convert tHours to 3-hour index (e.g., 1.5 hours -> index 0.5, interpolate between 0 and 1)
-	it0 := int(math.Floor(tHours / 3.0))
-	wt := (tHours - float64(it0*3)) / 3.0 // Interpolation weight within 3-hour window
+
+	// Время: tHours делим на шаг, чтобы получить индекс в кубе
+	tIdx := tHours / float64(d.ds.TimeStep)
+	it0 := int(math.Floor(tIdx))
+	if it0 < 0 {
+		it0 = 0
+	}
+	if it0 >= d.cube.t-1 {
+		it0 = d.cube.t - 2
+	}
+	wt := tIdx - float64(it0)
+
+	// ISA: высота → давление → индекс уровня
+	levels := d.ds.Levels
 	p := pressureFromAlt(alt)
 	ip0 := 0
-	for ip0+1 < len(pressureLevels) && pressureLevels[ip0+1] > p {
+	for ip0+1 < len(levels) && levels[ip0+1] > p {
 		ip0++
 	}
 	ip1 := ip0 + 1
-	wp := (pressureLevels[ip0] - p) / (pressureLevels[ip0] - pressureLevels[ip1])
+	if ip1 >= len(levels) {
+		ip1 = len(levels) - 1
+	}
+	wp := 0.0
+	if levels[ip0] != levels[ip1] {
+		wp = (levels[ip0] - p) / (levels[ip0] - levels[ip1])
+	}
+
 	fetch := func(ti, pi int) (float64, float64) {
 		u00 := d.cube.val(1, ti, pi, y0, x0)
 		u10 := d.cube.val(1, ti, pi, y0, x1)
@@ -41,6 +111,7 @@ func (d *dataset) uv(lat, lon, alt float64, tHours float64) (float64, float64) {
 		vxy := (1-wy)*((1-wx)*float64(v00)+wx*float64(v10)) + wy*((1-wx)*float64(v01)+wx*float64(v11))
 		return uxy, vxy
 	}
+
 	u0p0, v0p0 := fetch(it0, ip0)
 	u0p1, v0p1 := fetch(it0, ip1)
 	u1p0, v1p0 := fetch(it0+1, ip0)