Video/GIS registration in urban environments is necessary for establishing correspondences between real objects and geometric information in Geographic Information System (GIS) applications such as outdoor Augmented Reality (AR) and building texture acquisition. In this work, we present a registration system using a GPS prior and a skyline matching method to estimate the camera pose from images. A skyline rectification method through vertical vanishing point detection is also developed to enable arbitrary camera orientation, with non nul tilt. The proposed approach is robust, fully automatic and computationally inexpensive which makes it a possible solution for mobile device applications. The performance of our approach is demonstrated in several experimental evaluations. The possible refinement of camera location through a systematic method is also investigated.