These measurements are relatively inexpensive, although they require a more sophisticated surface system than is needed for directional measurements. Log plotting requires a depth-tracking system and additional surface computer hardware. Applications have been made in both reconnaissance mode, where qualitative readings are used to locate a casing or coring point, and evaluation mode. The main differences between MWD and wireline gamma ray curves are caused by spectral biasing of the formation gamma rays and logging speeds. When this method is used, the wellbore (which is generally inclined) is divided into multiple segments (often 4, 8, or 16). Incoming gamma counts are placed into one of the bins.