WiFi mapping: what a WiFi map actually tells you

WiFi mapping means recording what your WiFi radio hears, where it heard it, and how strongly - then drawing the result on a map. A WiFi mapper does the recording for you. Instead of standing in a room guessing whether the signal is "fine here", you end up with measured points you can look at, compare and argue from.

What goes into a WiFi map

Every time WifiMapper scans, your phone reports every WiFi network within range. For each one, WifiMapper stores:

• SSID - the network name you would see in your WiFi list.
• BSSID - the access point's own hardware address. This is what separates two radios broadcasting the same network name, so a mesh system maps as several access points rather than one.
• Signal strength - in dBm, from the phone's own radio, at that exact spot.
• Channel frequency - which tells you the band: 2.4 GHz, 5 GHz or 6 GHz.
• Security protocol - WPA2, WPA3, open, and so on.
• GPS position and time - the "where" and "when" that turn a scan into a map point.

Reading a WiFi signal strength map

On the WifiMapper map, every place you took a scan from is a blue dot. Choose an SSID and its samples turn red, sized by how strong the signal was - the stronger the reading, the bigger the dot. Three things fall out of that immediately:

• Where the access point is. Signal falls off with distance, so the tightest cluster of the biggest dots is very close to the radio itself. You do not need the router's location on a plan; the WiFi map finds it.
• How far the network really reaches. The outer edge of the red dots is the honest answer, as measured by a real client device rather than predicted by a coverage simulator.
• Where coverage drops out. A blue dot with no matching red dot means you scanned from there and that network did not answer. That is a WiFi dead spot, located on the ground.

WiFi mapping vs a WiFi heat map

A traditional WiFi heat map interpolates: it takes a handful of readings, smears colour between them, and shows a confident-looking wash that may be guessing over most of the floor. WifiMapper plots the measurements themselves. Nothing is coloured in where nothing was measured, which makes it far harder to talk yourself into coverage you do not have. Walk more, and the map simply gets denser.

What people map WiFi for

• Site surveys before a quote. Walk the building, see what is already there, and find the interference and the gaps before promising a design.
• Chasing a dead spot. Map the corridor, the warehouse aisle or the back bedroom where calls drop, and show exactly where the signal gives out.
• Placing a mesh node or repeater. Map first, and put the node where the signal is still good rather than where the power socket happens to be.
• Finding an unknown access point. An SSID you do not recognise is broadcasting from somewhere. Map it, follow the big dots, and you are standing next to it.
• Channel planning. Map the neighbours' networks and their frequencies before you pick a channel for your own.
• Proving it got better. Map before the change, map after, and compare.