Type codes and feature categories
A type code (also called a feature category — the two terms are interchangeable) is a short identifier that classifies a facility into the general kind of thing it represents: a 7-bar earth-covered magazine, an inhabited building, a public transportation route, and so on. The type code is the first thing the QD engine resolves when it begins an analysis. Once it knows the type code, it knows which subset of the criteria flow is even relevant — every later step (attributes, relationships, barricading, explosives) refines a path that started with the type code.
By the end of this lesson you should be able to:
- State the role a type code plays in the criteria path
- Recognize the categories of type codes available under DCMA criteria
- Predict how a type code change reshapes which attributes apply and which analysis codes are reachable
What a type code does
The type code answers the engine's first question: what kind of facility is this? That answer points the engine at a starting entry in the criteria flow before any other input is considered. Two facilities with identical attributes but different type codes start at different entries and can walk completely different criterion paths — even at the same explosive quantity and the same distance.
Examples from DCMA
A few representative type codes from the DCMA criteria set (DoD Manual 4145.26) — enough to get a feel for the catalog. Each criteria set (DCMA, DESR, NATO, ATF) ships its own list with overlapping but distinct entries.
| Code | Name | What it represents |
|---|---|---|
| ECM7 | ECM (7-Bar) | A 7-bar earth-covered magazine — the structural rating is part of the type code, distinct from ECM3 and ECMU |
| AGM | Above Ground Magazine | An above-ground magazine, open-air stack, or light structure |
| IHB | Inhabited Building | A building with people and no explosives — a classic ES |
| PTR | Public Transportation Route | A roadway, waterway, or other public route |
| ILD | ILD General | A distance-only code — applies the intraline distance criterion without modeling a specific ES facility |
| NQD | No-QD | A feature that does not require QD evaluation |
The full catalog is broader than this — storage variants (ECM3, ECMU, FRM), operating locations (EOL, IDS), other exposed sites (AUX, PLT, RAF), utilities (UTE, UTW, HZM), and additional distance-only codes (IBD, IMD, PTRD, FPD, IZD) all exist. Use the calculator's type code selector to browse the full set for whichever criteria you are working under.
Type codes gate which attributes apply
Attributes are scoped to the type code, so when you change the type code on a feature the calculator reloads the attribute set to match. Any attribute values that do not apply to the new type code are dropped, and any attributes the new type code requires that were not previously set fall back to default values. This is intentional — the criteria only ask the questions that matter for the current type, and the UI follows.
See Attributes for the next step in the engine's calculation flow.
Type code vs feature category
Throughout Siter and the calculator, type code and feature category refer to the same thing. The calculator and the engine's API tend to use type code (ECM7, IHB); the Siter UI tends to use feature category alongside the human-readable name (e.g., "ECM (7-Bar)"). When you see one term, treat it as a synonym for the other.
Try it
Open a calculator analysis and change the PES type code from AGM to ECM7 without changing anything else — same attributes, same explosives, same ES. The required distance, governing hazard, and analysis code should all shift, because the engine is now starting at a different entry in the criteria flow.
Related
- Attributes — what the engine asks about next, and how the attribute set depends on the type code
- Criteria path — the full chain from type code to analysis code
- Segments and sides — how a facility's geometry partitions into sides for analysis