Merge pull request #44 from MichelDequick/develop

TinyGPSPlus based LST calculator

Author: ClutchplateDude

Software/Arduino code/Sidereal.cpp

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+#include "Sidereal.hpp"
+
+// Constants for sidereal calculation       
+// Source: http://www.stargazing.net/kepler/altaz.html
+#define C1              100.46
+#define C2              0.985647
+#define C3              15.0
+#define C4              -0.5125
+#define J2000           2000
+
+static DayTime Sidereal::calculateByGPS(TinyGPSPlus* gps){
+    DayTime timeUTC = DayTime(gps->time.hour(), gps->time.minute(), gps->time.second());
+    int deltaJd = calculateDeltaJd(gps->date.year(), gps->date.month(), gps->date.day());
+    double deltaJ = deltaJd + ((timeUTC.getTotalHours()) / 24.0);
+    return DayTime((float)(calculateTheta(deltaJ, gps->location.lng(), timeUTC.getTotalHours()) / 15.0));
+}
+
+static const double Sidereal::calculateTheta(double deltaJ, double longitude, float timeUTC){
+    double theta = C1;
+    theta += C2 * deltaJ;
+    theta += C3 * timeUTC;
+    theta += C4;
+    theta += longitude;
+    return fmod(theta, 360.0);
+}
+
+static const int Sidereal::calculateDeltaJd(int year, int month, int day){
+    const int daysInMonth[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+
+    // Calculating days without leapdays
+    long int deltaJd = (year - J2000) * 365 + day; 
+    for (int i=0; i < month - 1; i++){
+        deltaJd += daysInMonth[i];
+    }
+
+    // Add leapdays
+    if (month <= 2){
+        // Not counting current year if we have not passed february yet
+        year--;
+    }
+    deltaJd += year / 4 - year / 100 + year / 400;
+    deltaJd -= J2000 / 4 - J2000 / 100 + J2000 / 400;
+    return deltaJd; 
+}

Software/Arduino code/Sidereal.hpp

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+#pragma once
+
+#include <math.h>
+#include <TinyGPS++.h>
+
+#include "DayTime.hpp"
+
+
+class Sidereal
+{
+ public:
+    static DayTime calculateByGPS(TinyGPSPlus* gps);
+
+ private:
+    static const double calculateTheta(double deltaJ, double longitude, float timeUTC);
+    static const int calculateDeltaJd(int year, int month, int day);
+};