A computer-implemented method for making measurements ahead of a drill bit, comprising: controlling activation of a tool disposed downhole, the tool having an arrangement of transmitter antennas (110-1; 110-2;... 110-(N-1); 110-N) and receiver antennas (110-1; 110-2;... 110-(N-1); 110-N) spaced apart operable in selected transmitter-receiver pairs; acquiring a deep signal from a deep measurement using a transmitter-receiver pair and one or more shallow signals from one or more shallow measurements using one or more other transmitter-receiver pairs; processing the one or more shallow signals, generating a modeled signal relative to regions adjacent sides and back of the tool; and forming a look-ahead signal substantially without contributions from the regions adjacent the tool by processing the deep signal with respect to the modeled signal; wherein processing the one or more shallow signals and forming the look-ahead signal includes one of: a) equalizing the one or more shallow signals in terms of geometrical factors to the deep signal such that difference between the deep signal and the equalized one or more shallow signals provides the look-ahead signal; or b) performing an inversion based on the one or more shallow signals and the deep signal such that the modeled signal is derived as an anticipated deep signal from the inversion, and subtracting the modeled signal from the deep signal to generate the look-ahead signal; or c) performing an inversion based on the one or more shallow signals without input from the deep signal, applying a signal resulting from the inversion to a forward modeling of a deep configuration to provide the modeled signal, and subtracting the modeled signal from the deep signal to generate the look-ahead signal, the method further including conducting another inversion using the look-ahead signal and parameters of layers around the tool to generate resistivities and positions of deep layers ahead of a drill bit corresponding to the tool, analyzing the look-ahead signal downhole during a drilling operation and making a geosteering decision downhole based on the analysis and generating resistivities and positions of deep layers as the drill bit moves ahead and stopping the drilling operation based on a determination that resistivity changes as the drill bit moves ahead exceeds a threshold for resistivity change. controlling activation of a tool disposed downhole, the tool having an arrangement of transmitter antennas (110-1; 110-2;... 110-(N-1); 110-N) and receiver antennas (110-1; 110-2;... 110-(N-1); 110-N) spaced apart operable in selected transmitter-receiver pairs; acquiring a deep signal from a deep measurement using a transmitter-receiver pair and one or more shallow signals from one or more shallow measurements using one or more other transmitter-receiver pairs; processing the one or more shallow signals, generating a modeled signal relative to regions adjacent sides and back of the tool; and forming a look-ahead signal substantially without contributions from the regions adjacent the tool by processing the deep signal with respect to the modeled signal; wherein processing the one or more shallow signals and forming the look-ahead signal includes one of: a) equalizing the one or more shallow signals in terms of geometrical factors to the deep signal such that difference between the deep signal and the equalized one or more shallow signals provides the look-ahead signal; or b) performing an inversion based on the one or more shallow signals and the deep signal such that the modeled signal is derived as an anticipated deep signal from the inversion, and subtracting the modeled signal from the deep signal to generate the look-ahead signal; or c) performing an inversion based on the one or more shallow signals without input from the deep signal, applying a signal resulting from the inversion to a forward modeling of a deep configuration to provide the modeled signal, and subtracting the modeled signal from the deep signal to generate the look-ahead signal, the method further including conducting another inversion using the look-ahead signal and parameters of layers around the tool to generate resistivities and positions of deep layers ahead of a drill bit corresponding to the tool, analyzing the look-ahead signal downhole during a drilling operation and making a geosteering decision downhole based on the analysis and generating resistivities and positions of deep layers as the drill bit moves ahead and stopping the drilling operation based on a determination that resistivity changes as the drill bit moves ahead exceeds a threshold for resistivity change. a) equalizing the one or more shallow signals in terms of geometrical factors to the deep signal such that difference between the deep signal and the equalized one or more shallow signals provides the look-ahead signal; or b) performing an inversion based on the one or more shallow signals and the deep signal such that the modeled signal is derived as an anticipated deep signal from the inversion, and subtracting the modeled signal from the deep signal to generate the look-ahead signal; or c) performing an inversion based on the one or more shallow signals without input from the deep signal, applying a signal resulting from the inversion to a forward modeling of a deep configuration to provide the modeled signal, and subtracting the modeled signal from the deep signal to generate the look-ahead signal,