1. A method for navigating a mobile system, the method implemented on one or more computer systems, comprising: matching landmarks for a first query image associated with a mobile device by: retrieving features from a global database for the first query image, wherein the global database comprises a plurality of landmarks and each landmark corresponds to a collection of 3-D features and corresponding 2-D features from which the 3-D features are computed; ranking landmarks of the plurality of landmarks by visual similarity to features of the first query image; selecting, from the global database, candidate landmarks that potentially match the features of the first query image; for each of the candidate landmarks selected from the global database: retrieving features in a local database for each of the candidate landmarks selected from the global database for the first query image, wherein the local database comprises a collection of 3-D features and corresponding 2-D features from which the 3-D features are computed for a specific landmark from the plurality of landmarks in the global database; performing robust pose estimation; performing bundle adjustment; determining an observation pose and covariance; and selecting one of the candidate landmarks as a matching landmark for the first query image; and responsive to selecting the matching landmark for the first query image, retrieving features from the global database for a next query image, selecting next candidate landmarks therefrom, and retrieving features in a local database for the next query image.