The direct transmission method is generally only used while measuring soils. It requires the operator to hammer an access hole with the drill rod. The gauge is placed on the surface with the source rod opening situated over the drilled hole. The operator depresses the trigger mechanism on the gauge handle and extends the source rod down into ground to the desired depth.

Because destructive testing, such as the drilled hole used with direct transmission, is not acceptable on an asphalt mat, the backscatter method is typically used on asphalt measurements. The operator depresses the trigger mechanism on the gauge handle to release the source rod but only lowers it to the first depth setting. This places the bottom of the source at the surface of the asphalt mat. The radiation can measure density to a depth of 3-4 inches.