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DQ analysis (actual distance)

QD analysis answers "how far apart should the PES and ES be?" DQ analysis answers "how much NEW can I site based on how far apart they are?". DQ is where the abstract required distance becomes a concrete compliance verdict for a real-world layout.

Learning objectives

By the end of this lesson you should be able to:

  • Distinguish QD (returns required distance) from DQ (returns allowable NEW)
  • Read the per-hazard DQ allowables and identify the governing constraint
  • Explain how DQ walks the same criteria flow as QD but with the input/output direction inverted
  • Distinguish DQ (capacity) from violation determination (QD-driven)

QD and DQ are reciprocal​

QD takes NEW as a known input and returns a required distance. DQ inverts the inputs: it takes the actual distance as known and returns the maximum allowable NEW. Both walk the same criteria flow — the engine is just answering a different question at the end.

AnalysisGiven inputReturnsUnits
QDNEWRequired distanceft
DQActual distanceAllowable NEWlbs

DQ is not the same as violation determination​

DQ and violation determination are related but distinct:

  • Violation determination uses QD: the engine compares the actual distance to the QD-required distance for the entered NEW, and flags the pair as violating when actual < required. This is what drives the violation indicators on the map and in the project results panel.
  • DQ analysis answers a different question: "given this actual distance, how much NEW could legally be sited here?" The DQ value is a capacity — the largest NEW the criteria would allow at this spacing.

A compliant pair has DQ allowable ≥ entered NEW (you have headroom). A violating pair has DQ allowable < entered NEW (the gap between the entered NEW and the allowable is the deficit). The QD comparison flags the violation; the DQ value quantifies how much NEW has to come off to clear it.

Per-hazard DQ values​

Like QD, DQ returns per-hazard allowable values alongside the governing one:

  • DQ — the bottom-line allowable NEW (the smallest of the per-hazard values)
  • blast_dq — NEW allowable under blast criteria
  • frag_dq — NEW allowable under fragmentation criteria
  • For divisions with supporting weights (1.2.1, 1.2.3), per-weight allowables: neq_dq, mce_dq, par_dq

The smallest per-hazard allowable governs — same logic as QD, inverted to the quantity domain.

Worked example: 1,000 lb 1.1 at 1,500 ft​

To see DQ in action, take the same pair from the QD worked example — 1,000 lb 1.1 at AGSU PES → IHB ES under DCMA — but set the actual distance to 1,500 ft.

The QD side says 1,250 ft is required at 1,000 lb, so the pair is compliant at 1,500 ft. The DQ side answers a different question: how much NEW could be sited at 1,500 ft?

The 1.1 DQ analysis path:

DQ Analysis, actual distance: 1500ft PES:AGSU to ES:IBD
Table AP2.T1. HD 1.1 IBD and PTRD
Note 4
Table AP2.T1. Note 4 Blast Criteria:
30,000 lbs < NEWQD ≤ 100,000 lbs: d = 40*NEWQD^(1/3)
1,243 ft < d ≤ 1,857 ft: NEWQD = d^3/64,000
K/Q Factor
DQ = (1500 / 40) ^ 3 == 52734.375
For exposures requiring HFD:
d ≥ 1,250 ft, weights are controlled by blast.

The engine inverts the K-factor. Where QD computed d = 40 × NEW^(1/3), DQ computes NEW = (d/40)³. At 1,500 ft that's (1500/40)³ = 37.5³ = 52,734 lb allowable.

Note the last two lines: at d ≥ 1,250 ft the HFD constraint is already satisfied (because 1,250 ft is the upper bound HFD produces for 1.1), so frag is no longer the active constraint at this distance. Blast governs the DQ allowable.

The DQ criteria path reflects that shift:

Table AP2.T1.
Table AP2.T1., Note 4
Table AP2.T1., Note 4 - Blast
C5.8.1.7.

governingCriteria is C5.8.1.7. — different from the QD result's governing criterion (C5.8.1.7.2.) for the same pair. Same criteria flow walked, different governing branch surfaced, because the input that drives the walk has changed.

Per-hazard DQ allowables for the same pair​

ResultValueMeaning
DQ (Required)52,734 lbThe smallest per-hazard allowable governs
blast_dq52,734 lbActive blast formula at this distance
frag_dq500,000 lbFrag is satisfied; allowable rises to the project's Max NEQ

The pair is well clear of frag — any NEW would satisfy the HFD rule at 1,500 ft. Blast governs the practical allowable. With 1,000 lb entered, the pair has more than 50× headroom on this constraint — useful capacity information that the QD-only view does not surface.

Why DQ matters in Siter​

In Siter, actual distances come from feature geometry on the map, not user-entered values. That makes DQ directly useful for capacity questions:

  • "What is the maximum NEW we could site at this PES given the closest ES?"
  • "If we reduce NEW from current to the DQ allowable, the QD arc shrinks below the actual distance and the violation clears"
  • "How much headroom do we have before this pair would start violating?"

Violations themselves still come from the QD side — the map's violation indicators reflect actual-vs-required distance comparisons. DQ tells you the capacity story alongside that compliance story.

Try it​

Set up a 1,000 lb 1.1 PES → IHB ES pair under DCMA with actual distance 1,500 ft (matching the worked example above). Run analysis and confirm:

  1. The QD result returns 1,250 ft required, with frag governing (C5.8.1.7.2.)
  2. The DQ result returns ~52,734 lb allowable, with blast governing
  3. The pair is compliant (actual ≥ required, and entered NEW < DQ allowable)

Now change the actual distance and re-run without changing NEW. Watch the DQ allowable shift in lockstep — closer = less allowable; farther = more allowable. Try setting actual distance below 1,243 ft and observe how the DQ formula changes (the engine drops out of the K=40 blast band and re-routes through the frag-controlled branch, the same way QD did at 1,000 lb).