Development of context-aware systems depends on the context definition and the context components. The entity location was always one of the main context components. For using location, a map service that provides possibilities of working with geographical information and showing results on the map is needed. The paper describes an implementation of a web mapping service for a mobile tourist guide, which is a context-aware service developed for supporting travelers before, during and after the trip. The mapping service provides possibilities of map showing, routing, geocoding, and has minimal license restrictions. The paper provides an analysis of existing web mapping systems such as Google, Microsoft, Yandex and describes implementation of free web mapping service for the mobile tourist guide based on OpenStreetMap, Leaflet, PostGIS, pgRouting, and Nominatim projects.