Calculate local gravity for a given latitude and elevation

LocalGravity.swift

func localGravity(latitude: Double, elevation: Double) -> Double {
    let a: Double = 0.0053024
    let b: Double = 0.0000058
    let l = latitude * .pi / 180
    
    let sinl: Double = sin(l)
    let sinl2: Double = sinl * sinl
    let sin2l: Double = sin(l * 2)
    let sin2l2: Double = sin2l * sin2l
    let t: Double = 1 / 1000000
    let ab = (1 + a * sinl2 - b * sin2l2)
    let g = (9.780327 * ab - 3.086 * t * elevation)
    
    return g / 10
}