Arduino dewpoint calculation

dewpoint.ino

// reference: http://wahiduddin.net/calc/density_algorithms.htm
double computeDewPoint2(double celsius, double humidity)
{
        double RATIO = 373.15 / (273.15 + celsius);  // RATIO was originally named A0, possibly confusing in Arduino context
        double SUM = -7.90298 * (RATIO - 1);
        SUM += 5.02808 * log10(RATIO);
        SUM += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
        SUM += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
        SUM += log10(1013.246);
        double VP = pow(10, SUM - 3) * humidity;
        double T = log(VP/0.61078);   // temp var
        return (241.88 * T) / (17.558 - T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
        double a = 17.271;
        double b = 237.7;
        double temp = (a * celsius) / (b + celsius) + log(humidity*0.01);
        double Td = (b * temp) / (a - temp);
        return Td;
}