55 lines
1.5 KiB
Go
55 lines
1.5 KiB
Go
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package weather
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import "math"
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// Attempts to complete missing fields that may not
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// be set by a specific provider, such as DewPoint and WindChill
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//
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// If enrich is called repeated with the same station ID, measurements
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// will be recorded to produce averages. This will be more stable
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// and support scaling if Redis is available
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// TODO: Implement average tracker
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func (u *WeatherUpdate) Enrich() {
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if u.WindChillF == 0 {
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u.WindChillF = CalculateWindChill(u.TempF, u.WindSpeedMPH)
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}
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if u.DewPointF == 0 {
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u.DewPointF = CalculateDewPoint(u.TempF, float32(u.Humidity))
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}
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if u.BaromAbsoluteIn == 0 {
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u.BaromAbsoluteIn = u.BaromRelativeIn
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}
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}
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func CalculateDewPoint(tempF, humidity float32) float32 {
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// Convert temperature from Fahrenheit to Celsius
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tempC := (tempF - 32) * 5 / 9
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// Calculate the dew point using the Magnus-Tetens approximation
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a := float32(17.27)
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b := float32(237.7)
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alpha := (a*tempC)/(b+tempC) + float32(math.Log(float64(humidity)/100))
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dewPointC := (b * alpha) / (a - alpha)
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// Convert dew point back to Fahrenheit
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dewPointF := (dewPointC * 9 / 5) + 32
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return dewPointF
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}
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func CalculateWindChill(tempF float32, windSpeedMPH float32) float32 {
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if windSpeedMPH <= 3 {
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// Wind chill calculation doesn't apply for very low wind speeds
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return tempF
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}
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// Formula for calculating wind chill
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return float32(
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35.74 + 0.6215*float64(tempF) -
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35.75*math.Pow(float64(windSpeedMPH), 0.16) +
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0.4275*float64(tempF)*
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math.Pow(float64(windSpeedMPH), 0.16))
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}
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