Wi-Fi heatmapping
The coverage plots everyone recognises — and an honest explanation of what they do and don't tell you. A heatmap is evidence, not a design.
What a heatmap actually shows
A Wi-Fi heatmap is a scaled plan of your building with measured radio data painted over it. Green usually means strong, red usually means weak, and that's roughly where most people's understanding stops — which is a problem, because the colours mean nothing at all until you know what's being plotted and what threshold the colour scale is set to.
The same survey data can produce a reassuring all-green plot or an alarming half-red one, depending entirely on where the scale is set. A heatmap drawn at −75 dBm will look excellent almost everywhere. The same building drawn at −65 dBm, which is what a handheld scanner or a voice handset actually needs to work reliably, can look very different. Neither plot is dishonest; only one of them is useful.
The plots that matter
Coverage is one plot. A survey worth paying for produces several, because a network can fail in several different ways and only one of them is weak signal.
| Plot | What it tells you | Why it matters |
|---|---|---|
| Signal strength (RSSI) | How loud the access point is where you're standing | The familiar one. Necessary, but on its own it is the least informative of the set. |
| Signal-to-noise ratio | How loud the signal is relative to everything else on the channel | The best single predictor of whether a connection is actually usable. Strong signal with a high noise floor still performs badly. |
| Channel overlap / co-channel | How much your own access points are competing with each other | The classic result of "we just added more access points". More radios on the same channels is less capacity, not more. |
| Capacity / channel utilisation | How busy the airtime is | Explains the site that has perfect signal everywhere and still crawls at nine in the morning. |
| Data rate | The speed devices can actually negotiate in each area | Where marginal coverage shows itself before users complain. |
| Roaming / AP coverage overlap | Whether a moving device can hand over cleanly | The one that matters most for scanners, trolleys, voice handsets and AGVs. |
A green heatmap that still fails
Three situations we see regularly, all of which produce a perfectly healthy-looking coverage plot:
- Capacity, not coverage. Signal is strong everywhere. The airtime is saturated because two hundred devices are sharing three access points. Adding more access points on the same channels makes it worse.
- Noise. Strong signal, but the noise floor is high — neighbouring networks, or a piece of plant throwing interference across the band. The signal-to-noise plot shows it immediately; the coverage plot never will.
- Roaming. Coverage is continuous, but the overlap between access points is wrong, so devices cling to a distant access point until the session drops. The user experiences it as "the Wi-Fi keeps dropping in the far aisle". The coverage plot says everything is fine.
This is why we don't sell heatmapping as a product on its own. The plots are an output of a survey, not a substitute for one — and a report that contains only a coverage heatmap is a report that hasn't done the analysis.
Common questions
Can we just buy a heatmap?
You can, and we'd rather explain why that's usually a false economy. A heatmap without the noise, capacity and roaming analysis behind it can tell you a network is fine when it isn't. If your budget is genuinely limited, ring us and describe the problem — a short conversation is often more useful than a cheap plot.
Can we see an example heatmap?
Yes. There's an anonymised example, walked through page by page, on the survey report page.
What signal level should we be designing to?
It depends on the devices. Laptops and phones tolerate weaker signal than handheld scanners, and voice handsets and AGVs are less tolerant again — they also need designed overlap so they can roam without dropping. A survey establishes the right target for your specific device mix rather than applying one number to the whole building, and the report states which threshold each plot is drawn at.
Do heatmaps show outdoor areas?
Yes — yards, car parks, quaysides and open ground are surveyed and plotted the same way. Outdoor propagation behaves differently and the design constraints are different (mounting, weatherproofing, power and containment to remote positions), so outdoor areas are scoped separately.
Will the heatmap show which access points to move?
The plots show where the problems are; the report says what to do about them. You get specific actions — move this access point, change this channel, reduce power here — with the measurements that justify each one.
Let's find out what your Wi-Fi is actually doing.
Book a survey and you get measured data, a design you can build to, and a number you can budget against — not an opinion.