  Smart cities are growing significantly due to the growth of smart connected
vehicles and Internet of Things (IoT) where a wide range of devices are
connected to share data. Online mapping is one of the fundamental services
offered in smart cities which enables the vehicle owners to find shortest or
fastest direction toward a destination thus reduces travel cost and air
pollution. However, existing online mapping services rely on centralized
servers, e.g., Google, which collect data from users to offer service. This
method is unlikely to scale with growth in the smart city participants and
introduces privacy concerns and data wall where data of the users is managed by
big companies. To address these challenges, in this paper we introduce DMap, a
blockchain-based platform where the users can share data in an anonymous
distributed manner with service providers. To the best of our knowledge, DMap
is the first distributed blockchain-based solution for online mapping. To
improve the scalability of the blockchain, we propose to use edge-computing
along with blockchain. To protect against malicious vehicles that may inject
false data, we define a reputation system where the collected data of the
vehicles is verified by monitoring the neighbor data. We introduce data
marketplace where users can trade their data to address data wall challenge.
