As useful as it would appear it is only in the update to Debrief 2001 that Debrief has been able to show properly sensor data.
A rudimentary way of showing bearing lines has been present for a number of years, but Debrief has not performed any useful processing on this data.
The following terms are used:
| Sensor | The sensor which recorded the data. Sensor data is grouped according to its sensor. This characteristic may be exploited by giving a unique sensor name to each track being recorded on a sensor - allowing tracks to be independently switched on and off. | |
| Sensor Contact | This is an individual contact recorded on a sensor, a single bearing line reaching from the sensor location (origin) along the contact bearing to the contact range. |
The sticky issue of whether to represent sensor data in absolute coordinates (where each line has it's own origin) or whether to represent the data in relative coordinates (where the sensor origin is assumed to be the current ownship position) is managed through the ability to enter NULL fields for the sensor location.
Support for relative coordinates is provided for two reasons:
Some sensor data sources may genuinely not contain positional data - allowing relative coordinates will ease the workload in these instances.
In the submarine plot-lock process it is quite common to experiment with a number of track-shifts until the hull-mounted sensor bearing fans tie up with the other vessel. By keeping the sensor data separate to the vessel data, the existing sensor data-file can be dropped into Debrief with the updated vessel track-file, allowing the user to perform a visual qualitative check on the shift applied.
Sensor data is loaded into Debrief in REP files, just like any other Debrief data. The line format is:
;SENSOR: YYMMDD HHMMSS.SSS AAAAAA @@ DD MM SS.SS H DDD MM SS.SS H BBB.B RRRR yy..yy xx..xx
;; date, ownship name, symbology, sensor lat/long (or the single word NULL), bearing (degs), range(yds), sensor name, label (to end of line)
As you can see, unlike other Debrief line formats, this format allows for NULL fields. Where the sensor latitude and longitude values are replaced by the single word NULL, Debrief plots this sensor contact using a relative origin.
When (as described above) Debrief plots data using a relative origin, it follows the following procedure:
The first time the sensor contact line is plotted, it examines its parent track to find the vessel position nearest to (or greater than) the sensor contact DTG.
The sensor contact then calculates the position of its far end relative to this origin
When first loaded, sensor data is not made visible, since with any reasonable volume of sensor data the plot quickly becomes illegible. Sensor data is switched on and off individually by accessing the sensor, via it's Track, from the Layer Manager.
It is once in snail trail mode that sensor data is most easily analysed. When in snail mode the Snail display mode performs the following processing:
For each Track being plotted, the display mode looks to see if it contains any Sensor data.
It then examines each list of Sensor data to see if it's visible If it is visible, it plots the current sensor contact (nearest to the Tote time), followed by the sensor contacts as disappearing contacts running back through the length indicated in the TrailLength parameter in the properties window.