Glossary

The terms Debrief uses in its interface, tools and documentation. The language section of the style guide says when to use them.

Adapted from DOMAIN_GLOSSARY.md in debrief/debrief-future, itself adapted from legacy Debrief's glossary, and corrected to the SRD. The changes are listed at the end.

Data

Plot. The unit of analysis: one exercise serial or deployment period, its tracks, annotations, sensor observations and narrative, with the history of every change made to it. Stored as GeoJSON in a STAC catalogue (SUB-05).

Plot file. The one file that holds a plot: its content, its island and its whole history. Send it to a colleague and the history goes with it, undo included; they add it to a catalogue with Add a plot file…. Other GeoJSON tools can read it (SUB-07, SUB-19).

Catalogue. A folder of plots, sources and supporting files, described in STAC. Each catalogue holds data of one protection level (SEC-02).

Source. A file imported into Debrief, such as a REP file or a legacy plot. Debrief never changes a source; a revision arrives as a new source (SUB-10). A catalogue keeps its sources, but they don't travel with a plot file: the plot's first step holds what was imported, and its history names each source.

Supporting file. Video, imagery, acoustic files and other content that is not geographic data, kept beside a plot (SUB-06).

History (in guides, provenance). The record of every operation that produced a plot: imports, tool runs, edits and deletions, with who or what made them (SUB-18 to SUB-24). Kept in the plot file, all of it, always.

Step. One change in a plot's history: what made it, who, when, and what it changed. A step is in the plot, undone (can be redone) or replaced by a later change (kept on record) (SUB-19, SUB-21).

Checksum (in guides). A short fingerprint of some data that changes if the data does. Each step of a plot's history carries one covering the step and the step before, and the current step records the checksum of the plot's content, so a history altered outside Debrief is noticed. The island is outside every checksum (SUB-19).

Time window. The period of the plot being looked at, one for the whole plot. Sensor data is shown only within it (CAP-28, CAP-29). Saved with the plot, but not part of its history: changing it is never undone.

Saved window. The time window as saved in the plot. A tool that moves current time outside it shows a wider or moved window instead, without saving it; the time controller says so, with Keep to save the window shown and Revert to show the saved window again (CAP-28).

Context tracks. Each track's whole line outside the time window, drawn thin and quieter so the whole picture stays in view. A plot draws them visible (at least 3:1 against the map), faint or hidden (CAP-29).

Island (in guides). View state saved inside the plot file, so it travels with the plot, but outside its history: never recorded, never undone. The time window is the first. Everything else in a plot, a track's colour and what is hidden included, is part of its history (SUB-22).

Feature. Anything in a plot: a track, an annotation, or a set of sensor observations. Used where a statement covers all three, as in "Plot features" in the outline; otherwise name the kind.

Fix. A single timestamped position of a platform, with course, speed and depth where known. Depth is positive down.

Track. The movement of one platform over time: its fixes in order.

Annotation. A line, area, circle, ellipse, label, marker, note or period of interest drawn on or attached to a plot, or chart furniture such as the north arrow (CAP-03). An annotation with only a time, such as a note or a period, has no position (CAP-04). How it looks (colour, line, fill, label) is part of the plot: changing it is a step in its history. Write annotation, not shape, in the interface.

Circle, ellipse (annotations). Every position at one range from a centre; or an ellipse about a centre, its longer axis along a true bearing. Ranges are measured along geodesics. Kept in the plot file with their exact centre and size, and a polygon approximating them so other GeoJSON tools see the area (CAP-03).

Chart furniture. What a chart carries besides its data: the scale bar, always drawn, and the north arrow, which a plot shows or not.

Timeline. The view listing a plot's time-only annotations, such as narrative notes and periods of interest, in time order. Choosing an entry moves current time to it (CAP-05). The SRD calls it the temporal view.

Named set. A saved selection of features, reusable as a selection or as a tool's input (TL-11).

Narrative. The log of events from each platform, imported from Word or PDF and combined on one time axis (CAP-19, CAP-20).

Serial. A period of an exercise, typically 4, 6, 12 or 24 hours.

Sensors and TMA

Sensor. A device on a platform that observes others: sonar, radar or visual.

Sensor observations (contacts, cuts). Measurements from a sensor, in Debrief usually bearings. Weeks of them may be held as one set (CON-02).

Bearing. The direction from one position to another, measured clockwise from true north. A relative bearing is measured from the platform's own heading. Debrief displays true bearings as three figures: 045.0°T.

Ambiguous bearing. A towed-array bearing that could be on either side of the array: two candidate bearings mirrored about the array's axis. The analyst resolves each to one side (CAP-22).

Bearing error. The uncertainty of a bearing, where the sensor data supplies it. Debrief can draw such a bearing as a wedge of that width (CAP-22).

TMA (target motion analysis). Estimating a target's course and speed from bearings, typically bearing-only from passive sonar. A solution is rooted in a selected period of bearings, and its positions match the bearing times (CAP-21).

Residual. The difference between a measured bearing and the bearing to the solution at the same time. Small, unpatterned residuals suggest a good solution.

Leg. A period of steady conditions. An ownship leg has steady course and speed; a bearing leg has a steady bearing rate. Changes of ownship leg give the geometry TMA needs.

SATC (semi-automatic track construction). Generating a TMA solution automatically from bearings. Lower priority than manual TMA (CAP-21).

Analysis

Tote. The table of relative geometry between one primary and several secondary platforms at current time: range, bearing and other measures (CAP-06).

Measure group. A named, reusable set of measures for a mode of analysis, defined by a study's lead analyst. The Tote is a view onto one (CAP-07).

CPA (closest point of approach). The time and range at which two platforms are nearest.

Current time. The instant, within a time range, that every view follows. Shared state, with selection and viewport (SUB-26).

Display window. The earlier name for the time window, when each layer was to have its own. There is now one time window for the whole plot (CAP-28, decision 12 Oct 2026).

Storyboard. A sequence of map views, each with a time and narrative comments, exported as offline HTML, a PowerPoint quad chart or video (CAP-13, CAP-14).

Tool. An analysis operation written in Python: Debrief builds its form and offers it when it applies (section 6 of the SRD).

Conventions

Time. Stored in UTC to the millisecond (SUB-01) and shown in Zulu time unless the analyst chooses a display zone.

Position. Latitude, positive north, and longitude, positive east, on WGS84. Debrief measures range and bearing along geodesics on the WGS84 ellipsoid, whatever the map's projection (SUB-03). Legacy Debrief used a flat-earth model, so its figures can differ by about 0.4% in range.

Units. Every stored quantity carries its unit. Analysts choose display units: knots, nautical miles, yards, metres, kilometres, degrees (SUB-02, SUB-04).

Direction	Degrees	Radians
North	0°	0
East	90°	π/2
South	180°	π
West	270°	3π/2

Changes from the earlier glossary

Earlier glossary	Now	Why
Times have microsecond precision	Millisecond precision; finer legacy times are truncated on import and the truncation recorded	SUB-01, EXT-14
Contacts carry frequency	Frequency is not imported; acoustic analysis stays in the acoustic replay application	CAP-22, EXT-03
Speeds include feet per second	Knots, metres per second, kilometres per hour	Schema unit enums
Track segments: core, TMA, planning, infill	Not yet in the v4 data model; TMA solutions are rooted in a bearing period	CAP-21
Depth in every location	Positions are latitude and longitude; a track may carry a depth series, positive down	Schema 0.0.4
World Location, World Speed, World Distance, World Vector	Position, quantities with units	Implementation names, not domain terms
Plot is a collection of tracks	Plot is the unit of analysis, a GeoJSON FeatureCollection in a STAC catalogue	SUB-05