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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →A Wi-Fi heat map is a color-coded view of a chosen wireless signal or quality measure across an area, usually shown over a floor plan. The colors only have meaning when you know the metric, its units, and the thresholds in the legend. A map may show measured survey results or a software model’s prediction; those are not the same thing.
What a Wi-Fi heat map shows
A heat map visualizes radio-frequency (RF) coverage across a space. The most common layer represents received signal strength (RSSI), but survey reports may also map signal-to-noise ratio (SNR) or noise floor. Cisco defines a heat map as a visual representation of wireless RF signal coverage in an area in its Catalyst Center floor-map guide.
The display is a view of a selected metric, not a direct verdict on whether every device or application will work well. Cisco explains that coverage depends on whether wireless clients can connect with adequate signal strength and quality to overcome interference; the required level varies by client and application. A strong-signal area can still have poor quality if noise or interference is high.
How to read the colors and thresholds
Start with the legend, not the colors. Green, yellow, or red has no universal Wi-Fi meaning: one tool might color a region green because it passes a configured RSSI threshold, while another layer uses a different metric or threshold. Check the metric name, units, frequency band, and threshold associated with each color.
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For example, Cisco’s site-survey guidance gives -67 dBm signal strength and 25 dB SNR as minimum recommendations for a voice-coverage use case. Those figures are not universal Wi-Fi requirements; the appropriate targets depend on the devices and applications the network must support. See Cisco’s WLAN site-survey guidance.
Also check which frequency band the map covers. Cisco Meraki notes that 2.4 GHz generally travels farther and penetrates obstacles better than 5 GHz. A map of 2.4 GHz alone may therefore fail to reveal weak 5 GHz coverage. Survey the bands and SSIDs that users will actually rely on, as discussed in Meraki’s channel-planning guidance.
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Predictive maps versus measured surveys
“Wi-Fi heat map” can describe different kinds of outputs. A predictive map estimates coverage from a floor plan and modeled network details; a measured survey records observations in the space. Cisco distinguishes software-based predictive surveys from field surveys in its site-survey guidance.
| Map or survey type | What it represents | Best use | Important limitation |
|---|---|---|---|
| Predictive | A software estimate based on the floor plan, modeled obstacles, access-point placement, antennas, and RF assumptions. | Initial planning, especially before installation. | It is a prediction, not an on-site measurement. Cisco warns that predictive results approximate actual RF intensity; modeled maps may not fully capture building-material attenuation or reflections. |
| Passive | A survey client listens to access-point transmissions without associating to an AP. | Observing beacon signal propagation and coverage. | It does not show uplink behavior, PHY-rate boundaries, or retransmissions. |
| Active | A survey client associates with an AP and exchanges traffic. | Validating client-like link behavior, including data-rate changes and retransmissions. | Results depend on the survey client and test setup, so they may not represent every device or operating condition. |
Cisco describes passive and active survey behavior in its Wireless Site Survey FAQ. For predictive maps specifically, Cisco’s Prime Infrastructure site-map documentation says the displayed RF intensity is approximate. Its Catalyst Center floor-map guide likewise describes 2D maps as approximations and explains that modeled floor components affect the prediction.
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How accurate is a Wi-Fi heat map?
Accuracy depends on how the map was made and how closely its inputs or survey conditions match the real network. A predictive map can guide placement, but the floor plan, wall materials, obstacle assumptions, AP locations, antenna orientation, and RF model all influence its estimate. Even a detailed 2D map cannot represent every real-world effect; Cisco notes that attenuation and reflections can change actual coverage.
A measured map is grounded in observations, but it is still specific to its survey method, equipment, and conditions. Passive measurements show what the survey client hears; active measurements add traffic exchange but reflect the behavior of that client and setup. A survey performed with different APs or client adapters from the planned deployment may be less representative. Cisco’s survey guidance recommends considering equipment, placement, interference, and rogue devices when interpreting results.
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What to check when comparing heat maps
Two maps are meaningfully comparable only when their underlying conditions and definitions are clear. Check these details before deciding that coverage improved or worsened:
- Survey method: predictive, passive, or active.
- Metric and threshold: RSSI, SNR, noise floor, or another layer, with its units and color limits.
- Band and SSID: confirm the same frequencies and network names are represented.
- Equipment: compare AP model, antenna, transmit power, and survey client.
- Floor-plan assumptions: check wall and obstacle inputs, AP locations, and antenna orientation, especially for predictive maps.
- Conditions: note whether the survey reflects representative operating conditions and interference.
Cisco recommends reports that identify coverage, SNR, and noise-floor maps with target thresholds and legends, alongside relevant information about interference and equipment placement. That context helps distinguish an actual coverage issue from a misleading or incomplete visualization.
Quick Recap
A practical way to use a Wi-Fi heat map
- Define the use case. Identify the applications and client devices the network must support, then choose suitable coverage and quality metrics and thresholds.
- Plan with a prediction when the space is unbuilt. Use the floor plan and modeled AP details to estimate coverage, and label the output as predictive.
- Validate after installation. Measure important areas with passive or active surveys using representative clients and operational network conditions.
- Review quality as well as signal. Consider SNR, noise, interference, and coverage overlap where relevant instead of relying on signal strength alone.
- Check every needed band and SSID. Do not assume a map for one band describes coverage on another.
- Investigate weak areas before changing the network. Use measurements and network context to identify the cause; a colored problem area does not by itself prove that low signal is the problem.
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