Received Signal Strength (RSS) geo-location is investigated under a Correlated Log Normal (CLN) model. Several parameters in the model may be unknown and the authors study their impact on both position estimation algorithms and the Cramer-Rao bound. Nuisance parameters in the CLN model include the path-loss exponent, the shadow fading standard deviation, and the shadow fading correlation. To estimate the user position, they compare the Steepest Descent and the Levenberg-Marquardt (LM) algorithms. Objective functions with and without weighting by the covariance matrix are considered. They prove from the CRLB that knowledge of the fading deviation and correlation is not needed by an optimal estimator.