Utilizing the Hopfield model for the altitude variation of the refractive index, we have found a convenient approach to the necessary integrals. The approach leads to simple analytic forms. The forms clearly illustrate that the dry term correction is directly proportional to surface pressure and quite insensitive to surface temperature. For elevation angles above 5¿ the range correction is proportional to P⋅ (Te+269.04)/(Te+273.16), where Te is the surface temperature in degrees Celsius and P is the surface pressure. The resulting equations and their derivations and limitations are described.