The World-Wide Sensor Web is generating tremendous amount of real-time sensor data streams, and will enable scientists to observe phenomena that are previously unobservable. As the concept of sensor web is to connect all the sensors and their data to achieve shared goals, improving the openness and accessibility of sensor data is important. Open Geospatial Consortium Sensor Observation Service (SOS) defines standard web service protocols for sharing sensor data online in an interoperable manner. However, the SOS has a relatively weak ecosystem, which makes it difficult to build and consume; and it only supports predefined queries. On the other hand, the OASIS Open Data Protocol (OData) has a strong ecosystem and flexible query functions. But the soft-typing approach of OData requires it to have a commonly agreed data model to be interoperable. As we find that the two standards can benefit from each other, we propose a sensor data mediator solution and define an SOS entity data model for OData (SOS-OData) to bridge these two standards. Our prototype demonstrates that the proposed system can convert between existing SOS services and SOS-OData services. As a result, we can not only consume SOS data with the flexible OData protocol, but can also easily build an SOS-compliant service with the strong OData ecosystem. We argue that the bridge between these two standards would lead us to the vision of open data for sensor web.