TMA algorithms are used to produce an estimate of range by analysing a sequences of sensor contacts which only contain bearing (and optionally range). The output of the algorithm is typically a series of estimated target locations with optional estimates for course, speed and depth. Uncertainty in bearing and range may be indicated by representing the target location as an ellipsoidal Target Uncertainty Area (TUA).
TUA contact data is always related to one of the currently loaded tracks, and may be represented either as an absolute location (at the centre of the ellipse) or as a range and bearing from the nearest point on that loaded track. The strategy for use of absolute versus relative data is described earlier in Section 11.1.4, “Preparing Sensor Data”.
TUA data is loaded into Debrief in REP files, just like any other Debrief data. The line format is:
;TMA_POS: YYMMDD HHMMSS.SSS AAAAAA @@ DD MM SS.SS H DDD MM SS.SS H TT...TT OOO.O XXXX YYYY CCC SSS DDD xx.xx ;; date, time, ownship name, symbology, tma lat, tma long, track name, ellipse orientation (deg from north), maxima (yds), minima (yds), course, speed, depth (m), label string ;TMA_RB: YYMMDD HHMMSS.SSS AAAAAA @@ BBB.B RRR.R TT...TT OOO.O XXXX YYYY CCC SSS DDD xx.xx ;; date, time, ownship name, symbology, bearing (deg), range (yds), track name, ellipse orientation (deg from north), maxima (yds), minima (yds), course, speed, depth (m), label string
There are two annotation format to represent TUA solutions (TMA_POS and TMA_RB). TMA_POS is used to define a TMA solution at a particular location, and TMA_RB is used to define a TMA solution at a specific range and bearing from the current ownship location at that specific DTG. Where a solution ellipse is not known the orientation, maxima and minima values can be represented by a single NULL value.
An alternate route to loading TUA data is to use the 'Generate TUA Ellipse' wizard. Right-click on a Track or the Solutions layer inside a track, and select the respective menu item. The time for the ellipse is taken from the Time Controller, though you may type in any time. Follow the steps, and when the wizard closes you will have created your TUA ellipse. Clearly, if you have lots of TUAs to load, you're better off by loading the data into Debrief via a data-files as described above.
When (as described above) Debrief plots data using a range and bearing, it follows the following procedure:
The first time the TUA solution is plotted, it examines its parent track to find the vessel position nearest to (or greater than) the TUA solution DTG.
The TUA solution then calculates the position of its centre relative to this origin
When first loaded, TUA data is not
It is once in snail trail mode that TUA 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 TUA data.
It then examines each list of TUA data to see if it's visible. If it is visible, it plots the current TUA solution (nearest to the Tote time), followed by the TUA solution as disappearing solutions running back through the length indicated in the TrailLength parameter in the properties window.