This feature allows you to record NMEA/AIS data for later playback.
Operation is simple. Turn on recording of NMEA data and that causes all NMEA/AIS data to be recorded to a file whenever an NMEA connection is present. The file is named according to the date/time it was started. Every 2 hours, the current recording is automatically closed and a new recording begun.
For playback, you can select a recording. This causes controls to appear on the Navigation tab that you can use to start/stop playing. You can adjust the slider to move to any point in the recording. During playback, all the displayed sensor data and AIS targets correspond to the data at the time it was played.
Note that when playing back the data, the chart display can be different than when originally recorded. For example, you can pan/zoom as you see fit, change various chart settings, etc.
The recordings are stored as files with an .nmea file extension. The file name includes the vessel name (if available via AIS AIVDO sentences) and the date/time at which the recording started. You can view them by selecting the Playback menu. If you want to save a recording by using various options to export.
The format of the recording file is essentially exactly the same as it was received from the NMEA/AIS stream so you may be able to use 3rd party tools to process the data. Note that certain proprietary sentences using the vendor code $PSIQ are inserted into the data to annotate with timing information and improve the efficiency of playback. The annotations can be ignored.
AIS data is only recorded from a primary NMEA/AIS feed. Data received from AIS Sharing or a Network AIS Feed is not recorded.
To start recording, simply turn Enable to ON. This setting is saved so whenever you use SEAiq with NMEA/AIS it will be recording data for you. This way you do not need to remember to start recording when you run SEAiq.
The Status field displays how long the current recording has been running and how many NMEA/AIS sentences it includes.
The current recording data cannot be viewed for playback. If you disable recording and then re-enable it, that will cause a new file to be opened for recording and the current one to be made available for playback.
Whenever a recording is started, all the current AIS targets will be automatically included in the recording so that playback can begin with all AIS included and you do not have to wait for AIS messages from each of them.
Recording for the current file will continue in the background even when you are playing back another recording.
You can stop playback by pressing the X button on the Navigate tab.
Conversion options include:
The error is defined as the maximum distance a polygon vertice will be shown from "actual" line. For instance, removal of a vertex from a polygon will result in new edges of the polygon; all vertices that were originally incident along that edge will be tested to see how far they are from the new edge.
The default is 1m. Lowering this value can have cause dramatic increase on the number of object when convering from a recording. This in turn can affect performance, in particular when 0m (no filtering) is set. Increasing the value can have a dramatic reducting in the number of objects.