MWD. A wireless system for making downhole measurements of [[azimuth]], [[inclination]], and tool facing from sensors mounted inside of a nonmagnetic [[drill collar]] located near the drill [[bit]]. Formation properties can be measured, such as: natural [[radioactivity]], [[resistivity]], and temperature. These measurements are sent to the surface by means of pressure pulses induced in the drilling [[mud]] by a mud-pulse transmitter, or stored downhole and brought to the surface when the bit and MWD collar are brought out of the hole.