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feat(weather): add dawn and dusk conditions based on solar sensor

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Detect twilight by checking when the solar radiation sensor reads low but
positive values (< 30 W/m²) while the sun is geometrically near the horizon
(sinusoidal fraction < 0.2 or outside model daylight hours). Morning/afternoon
local time distinguishes dawn from dusk without hard-coding sunrise/sunset times.
This commit is contained in:
Adriano Caloiaro 2026-04-11 12:28:30 -06:00
parent 47f7dad290
commit ef7c36af37
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2 changed files with 18 additions and 0 deletions
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@ -0,0 +1 @@
vendor/

17
weather/condition.go
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@ -11,6 +11,10 @@ type Condition struct {
// peakSolarRadiation is the approximate clear-sky maximum at sea level (W/m²).
const peakSolarRadiation = 950.0
// twilightSolar is the solar radiation threshold (W/m²) below which the sun is considered
// low in the sky, producing dawn or dusk conditions.
const twilightSolar = 30.0
// sunFraction returns the fraction of peak solar radiation expected at the given
// local time of day, using a simple sinusoidal model (sunrise ~6, sunset ~18).
// Returns 0 outside of daylight hours.
@ -52,8 +56,20 @@ func Infer(d Data, lat, lon float64) *Condition {
// Estimate local time from longitude (rough UTC offset).
utcMinutes := d.LastUpdated.Hour()*60 + d.LastUpdated.Minute()
localMinutes := utcMinutes + int(math.Round(lon/15))*60
localMinutes = ((localMinutes % 1440) + 1440) % 1440
fraction := sunFraction(localMinutes)
isDaytime := fraction > 0
isMorning := localMinutes < 720
// Dawn/dusk: sensor detects low but positive solar radiation while the sun is
// geometrically near the horizon (fraction < 0.2 or before/after model daylight).
// isMorning distinguishes the two without hard-coding sunrise/sunset hours.
if solar > 0 && solar < twilightSolar && (!isDaytime || fraction < 0.2) {
if isMorning {
return &Condition{"Dawn", "🌅"}
}
return &Condition{"Dusk", "🌇"}
}
if !isDaytime || solar < 10 {
if !isDaytime {
@ -81,3 +97,4 @@ func Infer(d Data, lat, lon float64) *Condition {
}
return &Condition{"Overcast", "☁️"}
}