feat(decart): interp

internal/numerics/vec.go

@@ -26,16 +26,6 @@ func PyMod(a, b float64) float64 {
 	return r
 }
 
-// GeoAdd returns y + k*dy with longitude wrapped to [0, 360). Latitude and
-// altitude accumulate linearly. This is the integrator's state-update step.
-func GeoAdd(y GeoVec, k float64, dy GeoVec) GeoVec {
-	return GeoVec{
-		Lat:      y.Lat + k*dy.Lat,
-		Lng:      PyMod(y.Lng+k*dy.Lng, 360),
-		Altitude: y.Altitude + k*dy.Altitude,
-	}
-}
-
 // GeoLerp linearly interpolates two geographic states by parameter l in
 // [0, 1]. Longitude takes the shorter great-circle arc.
 func GeoLerp(a, b GeoVec, l float64) GeoVec {
@@ -65,25 +55,6 @@ func Lerp(a, b, l float64) float64 {
 	return (1-l)*a + l*b
 }
 
-// AddGeo returns the component-wise sum a+b without longitude wrapping. Use it
-// to combine derivative (rate) vectors — rates accumulate linearly, unlike
-// positions, which wrap via GeoAdd.
-func AddGeo(a, b GeoVec) GeoVec {
-	return GeoVec{Lat: a.Lat + b.Lat, Lng: a.Lng + b.Lng, Altitude: a.Altitude + b.Altitude}
-}
-
 // EarthRadius is the spherical Earth radius (metres) used for horizontal
 // motion, matching the reference Tawhiri implementation.
 const EarthRadius = 6371009.0
-
-// WindToGeoRate converts eastward (u) and northward (v) wind in m/s at the
-// given latitude (deg) and altitude (m) into the geographic rate in deg/s on a
-// spherical Earth. The returned dLng diverges near the poles as cos(lat) → 0.
-func WindToGeoRate(u, v, lat, alt float64) (dLat, dLng float64) {
-	const degPerRad = 180.0 / math.Pi
-	const piOver180 = math.Pi / 180.0
-	r := EarthRadius + alt
-	dLat = degPerRad * v / r
-	dLng = degPerRad * u / (r * math.Cos(lat*piOver180))
-	return dLat, dLng
-}