Methods are described using resistivity ahead of a drill bit measurements obtained while drilling a subterranean well using a drilling mud. Resistivity data ahead of the bit is gathered during drilling and prior to penetrating a region of interest of a target subterranean formation using the drill bit and the drilling mud. The drill string progresses at target dip and azimuth angles toward the region on interest. The resistivity data is used to determine the top of the region of interest while the drill bit advances toward but does not penetrate the region. A core bit is then installed and a whole core of the region of interest obtained. Resistivity ahead of a drill bit measurements obtained while drilling a subterranean well may also be compared with conventional resistivity measurements obtained from one or more offset wells.