The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Systems that automatically route drivers between geographic locations generally utilize indications of distance, street names, building numbers, to generate navigation directions based on the route. For example, these systems can provide to a driver such instructions as “proceed for one-fourth of a mile, then turn right onto Maple Street.” However, it is difficult for drivers to accurately judge distance, nor is it always easy for drivers to see street signs. Moreover, there are geographic areas where street and road signage is poor.
To provide guidance to a driver that is more similar to what another person may say to the driver, it is possible to augment navigation directions with references to prominent objects along the route, such as visually salient buildings or billboards. These prominent object can be referred to as “visual landmarks.” Thus, a system can generate such navigation directions as “in one fourth of a mile, you will see a McDonald's restaurant on your right; make the next right turn onto Maple Street.” To this end, an operator can enter descriptions and indications of locations (e.g., street addresses, coordinates) for visual landmarks, so that the system can automatically select suitable visual landmarks when generating navigation directions.
However, not every landmark is visible at all times. For example, some billboards may be brightly illuminated at night but may be generally unnoticeable during the day. On the other hand, an intricate façade of a building may be easy to notice during the day but may be poorly illuminated and accordingly unnoticeable at night.