Accuracy is a budget, not a virtue
Counting projects treat accuracy as a single ladder where higher is always better and more expensive is always safer. That framing wastes money at the top and creates risk at the bottom, because different decisions tolerate error very differently. A trend line survives noise that would invalidate an occupancy limit. Before specifying a number, work out which tier your use case actually sits in, because the tier decides the technology, the device count, and most of the cost.
How accurate does a people counter need to be?
It depends on the decision the count feeds, and the honest answer spans four tiers. Trend and comparison work (is this month up on last, which store is busier) tolerates the most error, provided the error is consistent, because consistent bias cancels in comparisons. Operational decisions (staffing to hourly demand) need per-interval reliability rather than a good daily total. Financial and contractual numbers (conversion reporting, tenant reports, rent negotiations, funding claims) need defensible absolute accuracy with a documented test behind it. Safety and compliance numbers (occupancy limits, evacuation planning) need the tightest tolerance plus directional correctness, because the count controls an action.
The four tiers, and what each demands
Tier 1, trend and comparison. What matters is stability, not absolute truth: the same door counted the same way week after week. A consistent 4% undercount is nearly harmless here and a wandering 4% error is not, which is why drift detection matters more than headline accuracy. The drift question is a service question, covered in maintenance and SLA.
Tier 2, operational. Staffing and queue decisions consume hourly or sub-hourly numbers, so per-interval accuracy is the metric that counts, not the daily total that flatters most datasheets. A system that nets out to a beautiful daily figure while scrambling the hour-by-hour shape is useless for demand-based scheduling and short-horizon forecasting.
Tier 3, financial and contractual. When counts appear in conversion reporting, tenant statements, or a rent conversation, someone will eventually challenge them, so the requirement is absolute accuracy with a paper trail: a documented on-site test, a known method, and a repeat cadence. The metric definitions matter enormously here and are set out in people counting specifications, with the test itself in accuracy test methodology.
Tier 4, safety and compliance. An occupancy limit turns a count into an action, so both magnitude and direction must be right in real time, and the failure mode has to be safe (a system that silently stops counting must be detectable immediately). This tier justifies redundancy that would be extravagant in tier 1.
Specify the tier, then the number
The practical sequence: name the decisions the data will drive, assign each to a tier, take the highest tier that matters, then write the accuracy requirement in that tier's terms (consistency, per-interval, absolute, or real-time directional). This is the step that stops a specification from demanding tier 4 rigor for tier 1 reporting, which is the most common way counting budgets get inflated, and the reverse mistake, which is how tenant disputes start. Both faces of the problem are in the accuracy factors and, for the definitive treatment of the accuracy question itself, how accurate people counters are.
Where Ariadne fits
Ariadne's camera-free measurement serves all four tiers, and the honest way to establish which tier a deployment achieves at your site is a documented test on your own doors rather than a figure from us. For accurate visitor counting specifically, including what the "accurate" claim should mean before you buy, start at the accurate visitor counting guide.
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