Merge pull request #242 from vsimakhin/fix/night-time-polar-circle

fix night time calculation inside polar circle

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## [Unreleased]
+
+- Fix: Incorrect night time calculation when flying inside the polar circle
+
 ## [2.38.0] - 25.06.2024
 
 - Fix: Bug with columns for the extended PDF format, both A4 and A5.

README.md

@@ -15,6 +15,10 @@ You also can easily export all flight records into EASA style pdf format, print
 
 # Changelog
 
+## [Unreleased]
+
+- Fix: Incorrect night time calculation when flying inside the polar circle
+
 ## [2.38.0] - 25.06.2024
 
 - Fix: Bug with columns for the extended PDF format, both A4 and A5.
@@ -39,12 +43,6 @@ You also can easily export all flight records into EASA style pdf format, print
 - Fix: Add dynamic resizing for the charts on Stats pages
 - Fix: Instructor's hours for the Total Stats table were mixed up for the last 90 days and the last 12 months
 
-## [2.35.1] - 20.05.2024
-
-- Fix: Correct using styles and classes for the sidebar when switching between the pages
-- Update: Code cleanup, removing code for synchronization with mobile client (will not continue working on it)
-- Update: Update golang version (1.21.10) and go packages.
-
 The full changelog is [here](https://github.com/vsimakhin/web-logbook/blob/main/CHANGELOG.md)
 
 # Usage

internal/nighttime/nighttime.go

@@ -77,25 +77,40 @@ func (route *Route) FlightSpeed() float64 {
 	return route.RouteDistance() / route.FlightTime().Hours()
 }
 
-// SunriseSunset returns sunrise and sunset times
-func (place *Place) SunriseSunset() (time.Time, time.Time) {
-	sunrise, sunset := sunrise.SunriseSunset(place.Lat, place.Lon, place.Time.UTC().Year(), place.Time.UTC().Month(), place.Time.UTC().Day())
+// SunriseSunset returns sunrise and sunset times or time.Time{} if there is no night
+func (place *Place) SunriseSunset() (time.Time, time.Time, float64) {
+	sunElevation := sunrise.Elevation(place.Lat, place.Lon, place.Time)
+	sunRise, sunSet := sunrise.SunriseSunset(place.Lat, place.Lon, place.Time.UTC().Year(), place.Time.UTC().Month(), place.Time.UTC().Day())
+
+	noNight := time.Time{}
+	if sunRise == noNight || sunSet == noNight {
+		return noNight, noNight, sunElevation
+	}
+
+	aviationSunRise := sunRise.Add(time.Duration(-30) * time.Minute)
+	aviationSunSet := sunSet.Add(time.Duration(30) * time.Minute)
 
-	return sunrise.UTC().Add(time.Duration(-30) * time.Minute), sunset.UTC().Add(time.Duration(30) * time.Minute)
+	return aviationSunRise, aviationSunSet, sunElevation
 }
 
 // Sunrise returns aviation sunrise time
 func (place *Place) Sunrise() time.Time {
-	s, _ := place.SunriseSunset()
+	s, _, _ := place.SunriseSunset()
 	return s
 }
 
 // Sunset returns aviation sunset time (+30 minutes from apparent sunset)
 func (place *Place) Sunset() time.Time {
-	_, s := place.SunriseSunset()
+	_, s, _ := place.SunriseSunset()
 	return s
 }
 
+// Elevation returns sun elevation at the place
+func (place *Place) Elevation() float64 {
+	_, _, e := place.SunriseSunset()
+	return e
+}
+
 func (route *Route) NightTime() time.Duration {
 	speed := route.FlightSpeed()
 	speedPerMinute := speed / 60
@@ -107,29 +122,39 @@ func (route *Route) NightTime() time.Duration {
 }
 
 func nightSegment(start Place, end Place, maxDistance float64, speedPerMinute float64) time.Duration {
-	d := time.Duration(0)
 
 	distance := distance(start, end)
+
 	if distance > maxDistance {
 		// too long, let's split it again
 		mid := midpoint(start, end)
 		// calculate time at the mid point
 		flightTime := distance / 2 / speedPerMinute
 		mid.Time = start.Time.Add(time.Duration(flightTime) * time.Minute)
 
-		d = nightSegment(start, mid, maxDistance, speedPerMinute) + nightSegment(mid, end, maxDistance, speedPerMinute)
-	} else {
-		// get sunrise and sunset for the end point
-		// it could be calculated for the middle point again to be more precise,
-		// but it will add few more calculations and the error is not so high
-		sr, ss := end.SunriseSunset()
-
-		if end.Time.After(sr) && end.Time.Before(ss) {
-			d = time.Duration(0)
-		} else {
-			d = time.Duration(distance / speedPerMinute * float64(time.Minute))
+		return nightSegment(start, mid, maxDistance, speedPerMinute) + nightSegment(mid, end, maxDistance, speedPerMinute)
+	}
+
+	// get sunrise and sunset for the end point
+	// it could be calculated for the middle point again to be more precise,
+	// but it will add few more calculations and the error is not so high
+	sr, ss, elevation := end.SunriseSunset()
+
+	nightTime := time.Duration(distance / speedPerMinute * float64(time.Minute))
+
+	if sr.Year() == 1 && ss.Year() == 1 {
+		if elevation > 0 {
+			// Polar day, no night time
+			return 0
 		}
+		// Polar night, all time is night
+		return nightTime
+	}
+
+	// day time
+	if end.Time.After(sr) && end.Time.Before(ss) {
+		return 0
 	}
 
-	return d
+	return nightTime
 }