Glossary
Every metric the analysers print, with its formula and scope, plus the standards and terms the documentation uses.
Terms
- Event: one recording inside a session: one blast or one trigger.
- Session: one deployment of one unit, holding the events it captured and its recording settings.
- PPV, peak particle velocity: the largest velocity excursion on one axis, in mm/s. Most limits are written against it.
- PVS, peak vector sum: the largest instantaneous combined motion across all three axes, √(x² + y² + z²) evaluated sample by sample. Always at least as large as any single axis.
- PPA and PPD: peak particle acceleration (g) and peak displacement (mm), the same motion read before and after integration.
- Dominant frequency: the frequency at which an event concentrated its energy, read from the zero crossings around the peak or from the spectrum. Limits scale with it.
- Airblast overpressure: the peak air pressure from the blast, in dB relative to 20 µPa, read from the unit's microphone.
- VoD, velocity of detonation: how fast the detonation front travelled along a charge, in m/s, read as the slope of cable consumed against time.
- Continuous VoD: the instantaneous slope of the cable trace at every sample.
- Segmented VoD: the cumulative VoD from a zone's start to each of ten equally spaced points along it.
- Hole: one charged column, marked where the front entered it.
- Zone: the stretch of cable inside a hole that a VoD is fitted over. Stemming between decks is not a zone.
- Deck: one charge separated from the next by stemming.
- Cut: the cable-loss discontinuity between two consecutive charged zones, between holes or between decks of one hole.
- Cable calibration: the factor a VoD unit applies to turn what it senses into cable length. Formerly labelled "velocity factor".
- Trigger: the motion level at which a ViB unit starts recording an event.
- Peak hold: the largest motion a ViB unit saw in each window between triggers, recorded as the session histogram.
Vibration metrics
| Metric | What it is | Formula | Scope | Note |
|---|---|---|---|---|
| Peak Vector Sum | The largest instantaneous combined ground motion across all three axes — the single-number severity of this event. | max of √(x² + y² + z²), evaluated sample by sample | Full processed trace for the headline value; the current selection for the in-range card | The stored event PVS comes from the processing pipeline and can differ slightly from a selection recomputed in the browser. Compliance verdicts use the largest single-axis peak, not the vector sum — PVS is always ≥ any single axis. |
| Axis peak | The largest excursion on one axis over the current window, in the active view’s unit. | Signed extreme of the axis samples over the selection, or the full trace when nothing is selected | Follows the active dimension — g for acceleration, mm/s for velocity (PPV), mm for displacement | PPA, PPV and PPD are the same motion read through integration; regulatory limits are usually written against PPV (mm/s). |
| Zone peak (PVS) | The peak vector sum inside this zone’s window, captured when the zone was created or resized. | max of √(x² + y² + z²) across the zone’s sample range | This zone only | Stored at commit time — resizing the zone or re-running analysis recomputes it. It is not the event-level PVS. |
| Δ (ms) | How far this hole fired from its design — positive means it fired late. | Actual firing time minus planned initiation time | Rows matched in this timing import; the global overlay offset shifts all actual times together | |
| Dominant frequency | The tallest spectral peak per axis — where this event concentrated its energy. Most standards scale allowable PPV with frequency. | Frequency bin with the largest FFT magnitude for the axis | Acceleration spectrum of the full processed trace | |
| First-motion azimuth | The direction the ground first moved, read against the recorder's own axes: degrees from +X towards +Y, in the X–Y plane. A recorder can sit at any angle and nobody aims it at the shot, so this is a fact about the unit and the motion together, not yet a bearing to the blast. | Principal axis of the 3×3 second-moment matrix over the first quarter-cycle after onset; azimuth = atan2(Y, X) | Onset window of the plotted quantity, after the pre-trigger DC offset is removed | |
| Rectilinearity | How much of the first motion lies along one line: 1 is a straight line (a clean P arrival), 0.5 a circle in a plane. Readings under 0.7 are labelled weak and the direction should not be trusted. | 1 − (λ₂ + λ₃) / (2 λ₁) from the eigenvalues of the second-moment matrix (Jurkevics 1988) | The same onset window as the azimuth |
VoD metrics
| Metric | What it is | Formula | Scope | Note |
|---|---|---|---|---|
| Average VoD | Summary VoD for the whole hole. | One deck → that deck's VoD. Multiple decks → average of each deck's VoD. | All explosive decks in this hole. | Zone cards in the review column show each deck's VoD separately. |
| Avg VoD (zone mean) | Summary VoD for the hole based on its measured decks. | Average of each explosive deck's VoD. | Explosive decks only — stemming excluded; each deck weighted equally. | Matches Average VoD in the focus readout for the same hole. |
| Zone VoD | Pipeline VoD for one explosive deck. | OLS linear regression slope of consumed cable vs time across the zone span. | Single explosive zone only — not a hole-wide or selection-wide average. | |
| Gap / cut timing | Dead time between initiation events on the chart timeline. | Elapsed time from the end of the preceding explosive zone to the start of the next. | May include stemming traversal; shown between holes or between decks. | |
| Length | Cable distance covered in the current chart selection or zone context. | End cable position minus start cable position for the selected sample range. | Matches the highlighted chart range or anchored zone bounds. | |
| Duration | Elapsed recording time for the current chart selection or zone context. | End sample time minus start sample time for the selected range. | Includes any stall or gap samples inside the selected span. |
Standards
- AS 2187.2-2006 Appendix J (Australia): human-comfort levels for 95 % of blasts and for any blast, with structural assessment adopting BS 7385-2; airblast at 115 dB and 120 dB.
- USBM RI 8507 / OSMRE (United States): the blasting level criteria as the limit, the secondary criteria as a dashed reference; airblast at 133 dB (reference) and 140 dB (limit).
- BS 7385-2 and DIN 4150-3 are encoded for parity but not offered in the product.