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🔥 Heat maps: how they work & how to read them

This page explains how Merlin Cloud generates heat maps, what the colours mean, and how to use time/zone filters.

Leo avatar
Written by Leo
Updated over 5 months ago

How we generate heatmaps

  • Source: Positions detected within the camera’s view (or inside a selected zone).

  • Aggregation: We count visits per pixel grid (x, y) across your chosen date range.

  • Smoothing: Density is widened via morphological dilation and then Gaussian blur—you see clusters, not exact footprints.

  • Scaling: Each heatmap normalises its own scale (0–255) for the selected time range. Intensity is relative within that view, not comparable across different days by colour alone.

Colour legend

  • Blue → low activity

  • Green/Yellow → medium activity

  • Red → high activity

Because scaling is per-heatmap, keep the same date window when visually comparing areas or before/after changes.

Time & zone filters

  • Date range: The UI defaults to 30 days but any date range is supported.

  • Zones: Selecting a zone restricts the heatmap to that polygon; all widgets update to zone-specific data.

What a heatmap can (and can’t) tell you

Great for

  • Locating hotspots/coldspots and aisle dwell patterns

  • Seeing the impact of fixtures or entrance placement

  • Guiding merchandising & flow experiments

Not for

  • Person-level tracking or exact positions

  • Cross-period colour comparisons without the same time filter

  • Inferring staff vs shopper (unless you use enterprise options elsewhere)

Reading tips

  • Look for persistent red paths → high flow corridors.

  • Red near a kiosk without matching kiosk events may signal attraction but low engagement.

  • If a refit reduces red in an obstruction area, you likely improved throughput.

Privacy & storage (heatmap context)

  • No facial recognition. Full-body blur.

  • For heatmaps we store computed overlays + coordinates + metrics, not raw video frames. (Frame retention policies live in Privacy, data handling & retention.)

Limitations & quality

  • Accuracy drops with crowding, occlusion, harsh lighting, mirrors/reflective surfaces.

  • Mount cameras high, angled down, and verify results by a quick walk test.

  • If the camera goes offline, heatmaps won’t backfill for that gap (enterprise backfill optional).

Quick how-to

  1. Open a CameraHeatmap.

  2. Set date range (keep consistent for comparisons).

  3. (Optional) Choose a Zone to focus the view.

  4. Use insights to adjust layout or run a test; revisit with the same window to compare.

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