package grib

import "math"

// 47 pressure levels matching tawhiri configuration
var pressureLevels = []float64{
	1000, 975, 950, 925, 900, 875, 850, 825, 800, 775,
	750, 725, 700, 675, 650, 625, 600, 575, 550, 525,
	500, 475, 450, 425, 400, 375, 350, 325, 300, 275,
	250, 225, 200, 175, 150, 125, 100, 70, 50, 30,
	20, 10, 7, 5, 3, 2, 1,
}

func pressureFromAlt(alt float64) float64 { // ICAO ISA
	return 1013.25 * math.Pow(1-alt/44307.69396, 5.255877)
}