@@ -0,0 +117,4 @@
+// verts[0] before testing, so a polygon spanning the antimeridian is
+// handled correctly as long as the polygon itself spans no more than 180°
+// in longitude.
+func pointInPolygon(lat, lng float64, verts []PolygonVertex) bool {

@@ -0,0 +11,4 @@
+//
+// Useful for combining a vertical-rate model with a horizontal wind model
+// into a single propagator. Equivalent to Tawhiri's LinearModel.
+func Sum(models ...Model) Model {

@@ -0,0 +42,4 @@
+//	v = -k / sqrt(rho(alt)),  k = seaLevelRate * 1.1045,
+//
+// using the NASA atmosphere model for rho. Equivalent to Tawhiri's drag_descent.
+func ParachuteDescent(seaLevelRate float64) Model {

@@ -0,0 +52,4 @@
+// nasaDensity returns air density (kg/m^3) for an altitude in metres,
+// using the NASA simple atmosphere model.
+// See https://www.grc.nasa.gov/WWW/K-12/airplane/atmosmet.html.
+func nasaDensity(alt float64) float64 {

@@ -0,0 +102,4 @@
+//
+// If events is non-nil, an "above_model" event is emitted whenever the
+// wind field reports altitude above the highest pressure level.
+func WindTransport(field weather.WindField, events *EventSink) Model {

@@ -0,0 +262,4 @@
+	out := make([]RateSegment, 0, len(in))
+	for _, s := range in {
+		var until float64
+		switch s.Reference {

@@ -0,0 +4,4 @@
+
+// pymod returns a % b with Python semantics: the result has the sign of b,
+// so for b > 0 the result is always in [0, b).
+func pymod(a, b float64) float64 {

@@ -0,0 +17,4 @@
+//
+// Time is not stored in State — it is tracked separately by the integrator
+// and passed to Model.
+func stateAdd(y State, k float64, dy State) State {

@@ -0,0 +27,4 @@
+
+// stateLerp computes the linear interpolation of two states by parameter l
+// in [0, 1]. Longitude uses lngLerp so that wrap-around is handled.
+func stateLerp(a, b State, l float64) State {

@@ -0,0 +37,4 @@
+
+// lngLerp interpolates between two longitudes in [0, 360), choosing the
+// shorter great-circle arc.
+func lngLerp(a, b, l float64) float64 {