We report the first temperature dependent, non-destructive, wafer resistivity mapping and activation energy mapping measurements on high resistivity and semi-insulating 6H-SiC wafers. SiC wafers are defined as semi-insulating if their room temperature resistivity is greater than 1 x 10(5) Omega-cm [1]. The resistivity of samples investigated in the range from 10(7) Omega-cm to greater than 10(9) Omega-cm, at room temperature using a proprietary resistivity measurement system. A strong correlation is observed between non-destructive resistivity measurements and Hall effect measurements on corresponding regions. The spatial distributions of resistivity and activation energies obtained from temperature dependent measurements as well as the nature of the high resistivity behavior are discussed.