Recording a Default Session
We have made recording data as simple as possible. You can either set up a session individually or you can just press the green button and use the current system defaults. If you have setup a Default Boat, Route and Interface you can start recording by simply pressing the big green record button on the Session List page.
Follow the steps laid out in this section to record a session.
- To Record a Default Session
- Set a Default Boat (if you haven’t set it already)
- Set a Default Route (if you haven’t set it already)
- Set a Default Interface (if you haven’t set it already)
- Set the Timeslot Size in Seconds (assuming you don’t want it to be 60 seconds)
- Press the New Default Session Button
- Once you have started the process the Session Data window will open to show the information recorded/being recorded.
The table below explains the use of the fields on this screen.
| Field | Description | Required? |
|---|---|---|
| Session Description | Description of the session | Yes – Default recording will make a standard description using the system date and time. |
| Boat Name | Name of the boat that we are recording data for | Yes – Select from the boat definitions already setup in Rockit. Default recording will use the Boat with the Make Default Boat flag set to Yes |
| Route Name | Route the boat will follow | Yes – Rockit will create a route record based on the navigation data received from NMEA. In that scenario the route will be defined based on the system date and time. |
| Session Time Slot Size | The size of each sample time slot in seconds | Yes – The default is 60 seconds which works fine for most offshore sailing. If you want to get into the detail of individual events, lower this to 10–15 seconds. |
| Session ID | Each session has a unique ID. This is an internal system key for the Session Record. | Yes – system generated. |
Recording a Session With Non Default Settings
Its almost as straightforward to record a bespoke session.
Follow these steps to start recording.
Press the New Session button on the Session List window to create a new Session record.
- Select a Boat from the Boat drop list.
- Select a Route from the Route drop list
- Set the timeslot size using the up and down arrows on the Session Timeslot Size field. The default is 60 seconds. We would not recommend going below 15 seconds. This is the size of the sample period. 15 seconds means that a summary record will be create every 15 seconds.
- Enter something for the session description.
- Press the Save Session Button to save the record.
- Now press the Open Recording Session Data button. That will open the Session Data screen ready to start recording. The Status will be Collector : Stopped
- Press the Green Start Collector button to start the collection process.
The Status will switch to Collector : Running and the data flowing in will start to appear on the Log tab.
What Happens When You Start Recording ?
A couple of things will happen in the following sequence. This is irrespective of whether you are recording a defaults only session or one you have defined individually.
- First once the Data Collection Session screen has opened information about the status of the collection session will start to scroll down the Data Log list on the Diagnostic Data Tab.
- The Rockit Server will attempt to connect to the data source that has been defined for this session. See the section on Setting up Interfaces to understand the parameters that are required to make each different type of connection.
- Assuming the Rockit Server is able to connect it will start to read and record the messages that come in from the interface.
- We have defined a sample period in our session setup as ‘X’ seconds. Rockit will now collect messages for that timespan, using the ZDA or 126992 sentences to time the process.
- Once Rockit gets to the end of the sample phase the data aggregation process will run and a summary record for the time slot will be generated.
- The polar data will be updated to reflect the boats performance.
- The screens will be updated to display the newly collected data.
- A new sample period will be defined and Rockit will collect some more data for the new period. The process will repeat until the data collection process is stopped.
A Note On Time
If this is an NMEA 0183 connection it will be looking for a ZDA sentence. If its NMEA2000 it will be looking for PGN 126992.
These are effectively time signal messages from the NMEA session.
At some point we will write a paper on why we use this to drive the timing of the collection process rather than the internal system Clock but for now please take it as read that you will need these messages to be coming into Rockit for any collection activity to take place.
The first sample period will start at the point Rockit receives that ZDA or 126992 sentence and data will be recorded as being collected at the time on the sentence (not the PC or Rockit Server clock time).
We have found that the data can actually be running behind the actual point in time. There is effectively a lag between the NMEA device generating a sentence and it reaching the Rockit server database. The messages are effectively buffered. If you stop the Rockit Server data collection process it will more than likely continue to run until the buffer is completely read. The same will occur if you turn your instruments off, there will still be some data in the buffer to be read.