The Environmental message is intended for a wide variety of environmental data, including: current flow, water level, water temperature, visibility, and air gap. The message has the ability to provide both real-time and forecast data. A message version number is includes in the SR0 parameter to indicate which version of the message is being used.
In order to maximize flexibility, this message can be used to transmit from 1 to 8 sensor reports (a 1 sensor report uses 1 slot while a message with 8 sensor reports requires 5 slots). These sensor reports can be data from one location or from multiple locations. In addition, the data does not need to be sent at the same update rate allowing data that changes more rapidly to be sent more often than slowly changing data. Static data such as sensor position can be sent even less frequently.
The framework for the Environmental message is shown in Table 1. Each Environmental message has 56 bits of standard header and from 1 to 8 sensor reports (112 bits each). Each sensor report has 27 bits of common data leaving 85 bits for sensor data. The framework for the sensor report is shown in Table 3. There are a variety of sensor types that can be transmitted using this message; 4 bits gives 16 possible values, these are listed in Table 4. Details for the 85 bits of information for each sensor report type are detailed in Tables 5 – 15. All possibilities for each data parameter are described. In each case Sensor Not available means that the specific reading is not ever possible from that sensor location. Data Not available means that the reading is possible, but is not available for the current report (sensor could be malfunctioning).
All directions are relative to True North, all positions are WGS-84 Datum.
Table 1. Each Environmental message has 56 bits of standard header and from 1 to 8 sensor reports (112 bits each). Each sensor report has 27 bits of common data leaving 85 bits for sensor data. The framework for the sensor report is shown in Table 3
Table 3. There are a variety of sensor types that can be transmitted using this message; 4 bits gives 16 possible values, these are listed in Table 4. Details for the 85 bits of information for each sensor report type are detailed in Tables 5 – 15. All possibilities for each data field are described. In each case Sensor Not available means that the specific reading is not ever possible from that sensor location. Data Not available means that the reading is possible, but is not available for the current report (sensor could be malfunctioning). All directions are relative to True North, all positions are WGS-84 Datum.
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