Chapter 3. Analysing Data
- Table of Contents
- 3.1. Assigning tracks as primary and secondary
- 3.2. Automatic stepping
- 3.3. Using display modes
- 3.4. Measuring range and bearing
- 3.5. Viewing tracks in 3-dimensions
- 3.6. Track & Time toolbox
Analysis is the core function of Debrief. In this section of tutorial (at last) you are going to gain some familiarity with how Debrief can be used to analyse maritime exercises.
3.1. Assigning tracks as primary and secondary
3.1.1. Tote area
We'll have a brief explanation of the Tote at this point, using the image below.
The Tote area is used to show the current and relative status between two or more platform tracks. The information on the Tote is dynamic, showing vessel information at the time indicated in the Stepper Control (120500.00 in this case). The user is able to step through the tracks either manually (using the forward and backward buttons) or automatically (by switching on the timer button).
 | The primary and secondary tracks may not contain values exactly at the time in the time stepper control. For both the tote display and the plot-highlights, Debrief uses the data values recorded on or immediately after the indicated stepper time. |
One track currently loaded is assigned as the Primary track (the blue track in this instance), and then one or more tracks are assigned as Secondary tracks. The primary track always displays current course, speed and depth, as illustrated above. The secondary tracks displays this information, together with relative information such as Range and Bearing to the Primary track.
| It may be useful to remember that the Primary Track is usually assigned to the Target, thereby allowing a constant display of target bearing and range. |
There can be any number of secondary tracks. Debrief displays calculated results of the relationship between each one and the Primary Track. To see the relationship between secondary tracks, one of them must be set to the Primary track.
The following calculated data is presented, where the current point on each track is used for the calculation:
| Range | The range between the current point on the secondary track and the current point on the primary track using the earth model as described in the Glossary, displayed in the units stored in the Debrief Properties section of the Maintainer's Guide | |
| Bearing | The bearing between the points. | |
| Rel Bearing | The relative bearing between the heading of the participant in the secondary track, and the bearing to the primary track. The R and G characters at the start of the result are short for Red and Green, which indicate that the contact is to the Port or Starboard of the secondary track. | |
| Speed | The current speed of the indicated track (no actual calculation is performed here; the value from the data-file is displayed directly). | |
| Course | The current course of the indicated track (no actual calculation is performed here; the value from the data-file is displayed directly). | |
| Depth | The current depth of the indicated track (no actual calculation is performed here; the value from the data-file is displayed directly). | |
| Brg Rate | The instantaneous bearing rate of the primary track as observed from the secondary track. This value is explained in the Glossary. | |
| Time | Where track data is not recorded at regular steps, and tracks do not have data at the same time steps, there is a likelihood that the value displayed on the tote will not have been recorded at the current tote time. The time field shows the actual time at which the data value was recorded for that track. |
| When more than two tracks are loaded, the value n/a is shown in Tote calculations for the primary track which rely on other track data (range, bearing, rel bearing, brg rate). This is because it is unclear which inter-track relationship is being calculated. Where only two tracks are loaded (one primary and one secondary), the tote is able to show relative calculated data for both. |
3.1.2. Assigning Tracks
Back to the tutorial, setup Debrief to have Debrief running with the two tracks (boat1.rep and boat2.rep) visible. If there are any properties windows open on the Tote, close them at this point to save space, to have a view like that below.
If you right click on one of the tracks, you will see that on the popup menu provided, one of the commands is . Select this command, and the track will appear on the Tote. Now right-click on the other track, and select . The Tote should now look like the screenshot at the start of this demonstration (although the tracks may be the other way around).
You should probably have noticed the button at the foot of the Tote. This button automatically assigns tracks to the Tote. It takes a look at all of the data currently loaded and identifies which items may be placed on the Tote, then it makes one of these items the primary track, and the others as secondaries.
 | If you have more than two tracks, it can be quicker to assign the primary track manually and then press to assign the remaining tracks as secondary. |
3.1.3. Stepping forward
Now click on the Forward Button (that's the single right arrow). You should see the white highlight on each track move forward. If you can't see the highlight because part of the track is not visible, select the button. Now repeatedly click on the forward button, and you will see both the highlight move, and the information in the Tote update. The highlight and Tote are moving forward in one minute steps (one minute is the default). Also try clicking on the backward button, and the large step forward and backwards buttons (which contain double-arrows). The large step buttons by default move you in 10 minute steps. The buttons with an arrow and a line move you to the start or end of the time period. If the button is obscured (as in the screen-shot above) expand the Tote by dragging the separator bar to it's right. Note that the Tote can be completely hidden by clicking on the tiny left-arrow at the top of this bar.
With the introduction of Java 1.4 came wheel-mouse support. To move forward and backward in time through the serial just roll the wheel-mouse either way whilst either the Tote or the Chart has focus.
| Has focus means that this item was the last item clicked, and it is where Debrief is going to apply the next keyboard or mouse action. |
3.1.4. Notes
| It is not just tracks that can be added to the Tote, experiment with right-clicking on features on the plot and see if they have the "Set Primary Track" or "Set Secondary Track" commands available (although read the note below about these). In this way you can make a timed data point (represented by a Circle with a very small radius) the primary track, then add a number of vessel tracks as secondary tracks, and then as you move through the data you can constantly see the vessel range and bearings from this data point. This is particularly useful for seeing vessel ranges and bearings from a sensor such as a sonar buoy. Remember to set the DTG data for the data point to time(s) near those of the track - or else in your example Debrief will assume the "sonar buoy" is not yet active. |
 | A Circle currently only has a single "Centre" DTG value - so it will only be highlighted for 3 minutes either side of this point. Better results are obtained by using a Label (which has a picture of a luggage label on it), since Labels have start and finish DTGs. |
| The limits on the time period are the outer time limits of the visible data in the primary and secondary tracks currently displayed on the Tote, so following a filter operation (introduced later) the start/end times will be changed to reflect the time limits specified. |
| The keyboard can also be used for moving backwards and forwards, although Debrief has to know that it's the Stepper that you want the keys to control. So, after clicking on one of the forward/backward buttons you can then switch to keyboard control of the Tote as follows:
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