Pairwise key establishment is a fundamental service provided in secure sensor networks. However, due to resource constraints, establishing pairwise keys is not a trivial task. Recently, a random key pre-distribution scheme and its improvements have been proposed. The scheme proposed by Du et al. uses deployment knowledge to improve the performance and security of sensor networks. However, this scheme assumes group-based deployment in which groups of nodes are deployed from horizontal grid points. This assumption limits applications of the scheme. Therefore, in this paper, we propose an advanced key pre-distribution scheme in which different keys are logically mapped to two-dimensional positions, and the keys that are distributed to a node are determined by positions estimated using a node probability density function. The scheme can be applied to any deployment model provided the node probability density function has already been determined. Furthermore, simulation results show that our scheme achieves higher connectivity than Du et al.'s scheme.