Wireless location finding has emerged as a popular issue. As one of its branches, sensor networks perform as a fundamental tool to monitor inaccessible environment. However, the limitation on system bandwidth and energy resources motivates the use of data compression at each sensor. The estimation of time-difference-of-arrival (TDOA) is a key step in emitter location finding using sensor network. This paper demonstrates three compression approaches in deriving the TDOA estimation: fisher-information based method, wavelet transform method and a non-conventional monotone increase method. Simulation results are discussed in this paper. It is shown that the wavelet transform method outperforms the other two approaches, while more simulation on the combination of wavelet and fisher-information approach is still under investigation.