# Middleware for Plug and Play Integration of Heterogeneous Sensor Resources into the Sensor Web
## 6 Use Cases
### INTMARSIS Project  
The INTMARSIS project aims to monitor underwater seismic activity in real-time, allowing a precise estimation of actual earthquake scales. To achieve this goal a stand-alone seismic system with real-time telemetry was designed and tested [49]. One further objective was to assess the usability of OGC compliant standardized acquisition chains in underwater seismic applications.  
The INTMARSIS system, shown in Figure 21, is composed of mainly two components, an ocean bottom seismometer (OBS) and a surface buoy. The communication between the OBS and the surface buoy is performed by a stainless steel mooring line using inductive modems (SeaBird Electronics UIMM). This inductive modem provides low-bandwidth half-duplex communication through mooring lines (up to 7000 m) where regular cables are not practical [50]. The INTMARSIS system, deployed near the Catalan coast, is shown in Figure 22.  
Figure 21: INTMARSIS System overview. At the seafloor the OBS (Ocean Bottom Seismometer) acquires seismic data, storing it locally. A subsampled set of data is sent through the mooring line using an inductive modem. The surface buoy receives the real-time subsampled seismic data, which is transmitted to the Land Station server using a GSM link.  
Figure 22: INTMARSIS buoy (**left**) and INTMARSIS Ocean Bottom Seismometer (**right**).  
The OBS acquires 3 channels (X, Y and Z axis), taking 125 Samples per second (SPS) with a precision of 24 bits. However, due to the low bandwidth provided by the inductive modems (1200 bps), the full data set is not transmitted in real-time, but stored locally. The OBS controller generates a subsampled data set at 25 SPS which is transmitted thorough the inductive modem.  
In Figure 23 the INTMARSIS acquisition chain is depicted. The subsampled data set, alongside with OBS's technical data, is sent to the buoy through the inductive link. The inductive communication and the processing of the acquired data as well as internal sensors is performed by the master controller, hosted by the surface buoy. This software component is modelled as three different Virtual Instruments (VIs): OBS technical data, buoy technical data and a peak detector.  
Technical data from both OBS and buoy include internal temperature and humidity gathered by low-cost sensors integrated at the electronics board. Although this data is not scientifically relevant it may prove useful to the operators to detect hardware malfunctions and water leaks. The master controller collects the internal data and aggregates it into two different UDP streams, one for the buoy technical data and another one for the OBS technical data.  
The peak detector processes the seismic data and returns the maximum absolute value during a period of time (10 s by default). Each of these VIs is interfaced by an instance of the SWE Bridge and its data sent to an SOS server at the shore station using a GSM modem. The SDF associated with each VI are available at [37].  
The raw seismic data is sent in near real-time to the land station, where it is processed and stored in miniSEED files (a standard format for seismic data). This data is made publicly available through a FTP server. Although the raw seismic data is not stored by the SOS server, the peak values time series provides an indicator of the seismic activity. As the volume of data is several orders of magnitude lower than the raw seismic data, it is much easier to archive and display this data in Sensor Web environments. With this approach it is possible to discover and access data from the seismometer using Sensor Web components, and only download the seismic events instead of the whole data set.