A coverage heatmap becomes useful only when its metric, scale, and assumptions are visible. Color alone cannot tell you whether a design is adequate.
Read the legend before the floorplan
Confirm the metric name and units. Signal strength is commonly expressed in dBm; SNR and SINR are ratios in dB; overlap is a count. A red cell in one palette may mean strong signal, while red hatching in another may mean a threshold failure. Never transfer meaning between legends.
For dBm, values closer to zero are stronger. −45 dBm is stronger than −75 dBm. Use the dBm and milliwatt converter to see why a small-looking dB difference can represent a large power ratio.
Signal strength answers one question
Signal strength estimates the channel power available at the receiver. It does not by itself describe noise, interference, throughput, airtime, client capability, or application performance. A threshold should reflect the actual design requirement and device population, not a copied universal number.
SNR adds receiver noise
Signal-to-noise ratio compares the serving signal with the configured noise floor. Bandwidth and receiver assumptions affect noise. A map with generous signal strength can still have poor SNR if the assumed noise is high.
SINR adds modeled interference
Signal-to-interference-plus-noise ratio also includes the modeled energy from other transmitters using the same channel. It is only as complete as the scenario: an AP, radio, or external interferer that is absent from the model cannot contribute.
Overlap is neither automatically good nor bad
Overlapping coverage can support mobility and redundancy. Excessive co-channel overlap can increase contention. Review the winning transmitter, channel plan, target device behavior, and capacity objective together. A count without channel context is incomplete.
Dead zones are threshold results
A dead-zone layer identifies cells below a configured target inside defined coverage areas. If the polygon includes a stairwell that does not require service, or excludes a room that does, the percentage can be mathematically correct and operationally misleading.
Keep the plan readable
Walls, openings, and equipment markers should remain identifiable beneath the heatmap. Adjust overlay opacity when necessary, but do not use opacity to hide an unfavorable result. Check the same location across bands with consistent geometry and receiver settings.
Look for uncertainty, not just color
Pay attention to abrupt changes at material boundaries, edge regions, model extrapolation warnings, unverified material assignments, unusual antenna patterns, and areas sensitive to small AP movements. These are good candidates for a site survey or a conservative design margin.
Review checklist
- Metric and units are visible.
- Legend range and threshold are stated.
- Band, bandwidth, and receiver height are correct.
- Coverage-area boundaries match the requirement.
- Walls and AP locations remain legible.
- Model warnings and extrapolation are disclosed.
- Field validation is planned for consequential decisions.
See Calculate and read RF coverage for the SiteRF workflow.