Metrics and deviations

Every figure in the analyser comes from one model, so the number in the focus readout, the bar in the well, the (i) reading on the chart and the row in the CSV all agree. The model takes a view (cable length, continuous or segmented) and a subject (a zone, a hole, a free selection or the whole shot) and returns the figures that view of that subject deserves.

The figures

• Zone VoD is the slope of a straight line fitted through the cable trace across the zone, by least squares. It is the authoritative velocity for a deck. R² says how straight the samples were; a clean detonation reads 0.999 or better.
• Average VoD for a hole is the mean of its zone VoDs, each deck weighted equally. It is never a single regression across the gaps between decks, because stemming would drag the slope down.
• Cable used and Length are end position minus start position over the subject; Duration is the sample span in time. Stalls and gaps inside the span are included.
• Gap or cut timing is the dead time from the end of one charged zone to the start of the next, between holes or between the decks of one hole.
• On the continuous view a section also reports its mean, median, min and max, the share of samples steady within 10 % of the median, the final cumulative VoD and the run-up over the first tenth.

Every value has an info icon with its formula, its scope, and why it can differ from a similar label elsewhere.

Deviations

Each zone is compared three ways and the results appear on its card and in the export:

• vs hole: this zone against the average of its hole's zones.
• vs blast: this zone against the average across the shot.
• vs plan: this zone against the planned VoD of the product loaded in its hole, when a blast plan is attached.

A zone more than 10 % from its hole or blast average is flagged. The blast overview in the full-screen well shows every zone's VoD by hole so the outliers are visible in one glance, and the coefficient of variation says how spread the readings are as a share of their mean.

Confidence

A zone's confidence dot is green, amber or red according to how much cable the fit was measured over, against the unit's specification. Quote a red or amber zone's velocity with that caveat.

Cable calibration

The unit does not measure metres directly. Cable calibration is the factor it applies to turn what it senses into cable length; it is set on the unit for the cable in use and recorded with the session. You can read it in the event information panel and in the session settings. A wrong calibration scales every VoD in the event by the same ratio, so if the figures are uniformly high or low, check it before anything else.

Version and re-analysis

The event information panel shows the analysis engine version that produced these figures. When a newer engine is available the analyser offers to update; see Reports and exports.