Function predictGeo

shared/src/aim.ts:195–217

(k: Kinematics, dtSec: number)

 * deadReckon conventions, but in geodetic coordinates and with altitude.
 */
export function predictGeo(k: Kinematics, dtSec: number): GeoPoint {
  let east = 0;
  let north = 0;
  if (k.trackDeg != null && k.gsKt != null && k.gsKt > 0 && dtSec !== 0) {
    const v = k.gsKt * KT_TO_MS;
    const tr = k.trackDeg * DEG;
    const w = (k.turnRateDps ?? 0) * DEG; // rad/s
    if (Math.abs(w) > 1e-4) {
      // Constant-rate turn: integrate the arc.
      east = (v / w) * (Math.cos(tr) - Math.cos(tr + w * dtSec));
      north = (v / w) * (Math.sin(tr + w * dtSec) - Math.sin(tr));
    } else {
      east = v * Math.sin(tr) * dtSec;
      north = v * Math.cos(tr) * dtSec;
    }
  }
  const altM = k.altM + ((k.vRateFpm ?? 0) * FT_TO_M / 60) * dtSec;
  return {
    lat: k.lat + north / 110540,
    lon: k.lon + east / (111320 * Math.cos(k.lat * DEG)),
    altM,
  };
}

/**
 * Turn-rate estimate (deg/s) from a short track history, with angle