v1: Live ADS-B radar with detail panel, units, legend, proximity LED alert

src/radar_math.cpp

@@ -0,0 +1,49 @@
+#include "radar_math.h"
+#include <math.h>
+
+namespace RadarMath {
+
+namespace {
+    constexpr double EARTH_RADIUS_KM = 6371.0088;
+    constexpr double DEG2RAD = M_PI / 180.0;
+    constexpr double RAD2DEG = 180.0 / M_PI;
+}
+
+PolarCoord toPolar(double lat0, double lon0, double lat1, double lon1) {
+    double phi1 = lat0 * DEG2RAD;
+    double phi2 = lat1 * DEG2RAD;
+    double dPhi = (lat1 - lat0) * DEG2RAD;
+    double dLambda = (lon1 - lon0) * DEG2RAD;
+
+    // Haversine
+    double a = sin(dPhi / 2) * sin(dPhi / 2) +
+               cos(phi1) * cos(phi2) * sin(dLambda / 2) * sin(dLambda / 2);
+    double c = 2 * atan2(sqrt(a), sqrt(1 - a));
+    double distanceKm = EARTH_RADIUS_KM * c;
+
+    // Initial bearing
+    double y = sin(dLambda) * cos(phi2);
+    double x = cos(phi1) * sin(phi2) - sin(phi1) * cos(phi2) * cos(dLambda);
+    double bearing = atan2(y, x) * RAD2DEG;
+    bearing = fmod(bearing + 360.0, 360.0);
+
+    return PolarCoord{ static_cast<float>(distanceKm), static_cast<float>(bearing) };
+}
+
+ScreenPoint toScreen(const PolarCoord& polar, int16_t centerX, int16_t centerY,
+                     int16_t radiusPx, float rangeKm) {
+    float clampedKm = polar.distanceKm > rangeKm ? rangeKm : polar.distanceKm;
+    float r = (clampedKm / rangeKm) * radiusPx;
+
+    // bearing 0 = North = "up" on screen = negative Y direction.
+    double rad = polar.bearingDeg * DEG2RAD;
+    float dx = r * sin(rad);
+    float dy = -r * cos(rad);
+
+    return ScreenPoint{
+        static_cast<int16_t>(centerX + dx),
+        static_cast<int16_t>(centerY + dy)
+    };
+}
+
+} // namespace RadarMath