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heat index with refinements from NWS for lower values #154

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heat index with refinements from NWS for lower values #154

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16 changes: 14 additions & 2 deletions DHT.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -175,9 +175,12 @@ float DHT::computeHeatIndex(bool isFahrenheit) {
}

/*!
* @brief Compute Heat Index
* Using both Rothfusz and Steadman's equations
* @brief Compute Heat Index (based on Robert G. Steadman tables)
* Using Rothfusz equations with refinements by the NWS
* (http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml)
* and NWS algorithm that respects lower values of temperature
* and humidity
* (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3801457/)
* @param temperature
* temperature in selected scale
* @param percentHumidity
Expand All @@ -193,6 +196,15 @@ float DHT::computeHeatIndex(float temperature, float percentHumidity,
if (!isFahrenheit)
temperature = convertCtoF(temperature);

if(temperature <= 40) {
return isFahrenheit ? temperature : convertFtoC(temperature);
}

float varA = -10.3 + 1.1 * temperature + 0.047 * percentHumidity;
if (varA < 79) {
return isFahrenheit ? varA : convertFtoC(varA);
}

hi = 0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) +
(percentHumidity * 0.094));

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