In this paper, we present a signal acquisition and verification methodology to code a performance evaluation study of several non-conventional spectral estimation techniques for spectrum sensing, with the objective of detecting weak GNSS signals transmitted in high noise conditions. Traditionally, the Fast Fourier Transform has been used as a mechanism for performing correlation operations in the spectral domain for Global Navigation Satellite System (GNSS) signal acquisition. However, non-conventional techniques have been implemented to increase the robustness of the detector in low signal-to-noise ratio (SNR) environments. We implemented a Global Positioning System (GPS) signal receiver in GNU Radio to compare non-conventional spectral estimation techniques such as Burg, Yule-Walker, and Correlogram, for the purpose of detecting real GNSS signals under higher noise conditions.