1bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey/* 2bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * Copyright (C) 2010 The Android Open Source Project 3bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * 4bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * Licensed under the Apache License, Version 2.0 (the "License"); 5bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * you may not use this file except in compliance with the License. 6bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * You may obtain a copy of the License at 7bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * 8bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * http://www.apache.org/licenses/LICENSE-2.0 9bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * 10bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * Unless required by applicable law or agreed to in writing, software 11bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * distributed under the License is distributed on an "AS IS" BASIS, 12bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * See the License for the specific language governing permissions and 14bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * limitations under the License. 15bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey */ 16bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 17bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzheypackage com.android.server; 18bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 19bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzheyimport android.text.format.DateUtils; 20bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzheyimport android.util.FloatMath; 21bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 22bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey/** @hide */ 23bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzheypublic class TwilightCalculator { 24bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 25bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey /** Value of {@link #mState} if it is currently day */ 26bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public static final int DAY = 0; 27bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 28bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey /** Value of {@link #mState} if it is currently night */ 29bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public static final int NIGHT = 1; 30bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 31bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float DEGREES_TO_RADIANS = (float) (Math.PI / 180.0f); 32bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 33bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // element for calculating solar transit. 34bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float J0 = 0.0009f; 35bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 36bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // correction for civil twilight 37bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float ALTIDUTE_CORRECTION_CIVIL_TWILIGHT = -0.104719755f; 38bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 39bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // coefficients for calculating Equation of Center. 40bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float C1 = 0.0334196f; 41bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float C2 = 0.000349066f; 42bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float C3 = 0.000005236f; 43bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 44bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final float OBLIQUITY = 0.40927971f; 45bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 46bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // Java time on Jan 1, 2000 12:00 UTC. 47bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey private static final long UTC_2000 = 946728000000L; 48bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 496fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey /** 506fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey * Time of sunset (civil twilight) in milliseconds or -1 in the case the day 516fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey * or night never ends. 526fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey */ 53bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public long mSunset; 54bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 556fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey /** 566fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey * Time of sunrise (civil twilight) in milliseconds or -1 in the case the 576fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey * day or night never ends. 586fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey */ 59bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public long mSunrise; 60bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 61bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey /** Current state */ 62bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public int mState; 63bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 64bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey /** 65bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * calculates the civil twilight bases on time and geo-coordinates. 66bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * 67bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * @param time time in milliseconds. 68bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * @param latiude latitude in degrees. 69bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * @param longitude latitude in degrees. 70bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey */ 71bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey public void calculateTwilight(long time, double latiude, double longitude) { 72bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final float daysSince2000 = (float) (time - UTC_2000) / DateUtils.DAY_IN_MILLIS; 73bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 74bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // mean anomaly 75bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final float meanAnomaly = 6.240059968f + daysSince2000 * 0.01720197f; 76bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 77bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // true anomaly 78bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final float trueAnomaly = meanAnomaly + C1 * FloatMath.sin(meanAnomaly) + C2 79bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey * FloatMath.sin(2 * meanAnomaly) + C3 * FloatMath.sin(3 * meanAnomaly); 80bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 81bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // ecliptic longitude 82bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final float solarLng = trueAnomaly + 1.796593063f + (float) Math.PI; 83bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 84bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // solar transit in days since 2000 85bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final double arcLongitude = -longitude / 360; 86bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey float n = Math.round(daysSince2000 - J0 - arcLongitude); 87bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey double solarTransitJ2000 = n + J0 + arcLongitude + 0.0053f * FloatMath.sin(meanAnomaly) 88bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey + -0.0069f * FloatMath.sin(2 * solarLng); 89bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 90bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey // declination of sun 91bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey double solarDec = Math.asin(FloatMath.sin(solarLng) * FloatMath.sin(OBLIQUITY)); 92bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 93bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey final double latRad = latiude * DEGREES_TO_RADIANS; 946fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey 956fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey double cosHourAngle = (FloatMath.sin(ALTIDUTE_CORRECTION_CIVIL_TWILIGHT) - Math.sin(latRad) 966fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey * Math.sin(solarDec)) / (Math.cos(latRad) * Math.cos(solarDec)); 976fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey // The day or night never ends for the given date and location, if this value is out of 986fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey // range. 996fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey if (cosHourAngle >= 1) { 1006fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mState = NIGHT; 1016fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mSunset = -1; 1026fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mSunrise = -1; 1036fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey return; 1046fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey } else if (cosHourAngle <= -1) { 1056fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mState = DAY; 1066fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mSunset = -1; 1076fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey mSunrise = -1; 1086fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey return; 1096fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey } 1106fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey 1116fd5e0ac51021d55beb2c1f6f184469311301711Bernd Holzhey float hourAngle = (float) (Math.acos(cosHourAngle) / (2 * Math.PI)); 112bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 113bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey mSunset = Math.round((solarTransitJ2000 + hourAngle) * DateUtils.DAY_IN_MILLIS) + UTC_2000; 114bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey mSunrise = Math.round((solarTransitJ2000 - hourAngle) * DateUtils.DAY_IN_MILLIS) + UTC_2000; 115bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 116bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey if (mSunrise < time && mSunset > time) { 117bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey mState = DAY; 118bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey } else { 119bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey mState = NIGHT; 120bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey } 121bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey } 122bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey 123bfca3a0056a42bde672c8ade83f13f139149f756Bernd Holzhey} 124