1. A system for determining a location of a landmark for use in navigation of an autonomous vehicle, the system comprising: at least one processor programmed to: receive a measured position of the landmark; determine a refined position of the landmark based on the measured position of the landmark and at least one previously acquired position for the landmark, wherein the measured position and the at least one previously acquired position are determined based on acquisition, from a camera associated with a host vehicle, of at least one environmental image associated with the host vehicle, analysis of the at least one environmental image to identify the landmark in the environment of the host vehicle, reception of global positioning system (GPS) data representing a location of the host vehicle, analysis of the at least one environmental image to determine a relative position of the identified landmark with respect to the host vehicle, and determination of a globally localized position of the landmark based on at least the GPS data and the determined relative position; selectively preclude transmission of the refined position of the landmark or the measured position of the landmark to a server, the server storing a sparse data model including landmark position information, based on at least one value indicative of a determined confidence level; and selectively preclude transmission of a distance between two measured landmark positions to the server based on the at least one value indicative of the determined confidence level.