An infrared imager measures the radiant energy of an object and converts the data from the infrared region of the electromagnetic spectrum to the visible region of the electromagnetic spectrum. The result is a thermographic image of the object, from which temperature information can be gathered. Only the surface of an object can be imaged, and therefore only the surface temperature can be measured by the radiometer. This characteristic of infrared imaging can pose a problem when the temperature beneath a surface is pursued. Even in cases where a subsurface heat source makes a distinct thermal pattern on the surface that is imaged, the measured surface temperature is not necessarily the same as the actual source temperature. The surface temperature combined with thermodynamic principles and related material properties provides enough information to calculate the subsurface temperature, and so a thermographer has the ability to image a surface to determine the temperature beneath it. A practical application in this area is imaging the ground to locate and calculate the temperature of buried steam lines used in large heating distribution systems found in cities and college campuses. Presented here are formulas for calculating the heat loss and temperature of a buried steam line.