Find Your Wi-Fi Dead Spots by Walking the Building

The usual way to find a Wi-Fi dead spot is to stand somewhere, watch a video buffer, and move two feet to the left. Everyone has done the walk. Nobody writes down where they were standing.

Proper survey software solves this and costs thousands of dollars, which makes sense if you survey buildings for a living and makes no sense at all if you have one property and four access points.

HollowMap is our answer to the small version of that problem. It is free, and the working model is simple: you walk the site holding a device, and every few steps it records where you are and what the signal was like there.

Set the server down in the right place

This is the step people get wrong, and it quietly ruins the numbers.

Run the HollowMap desktop app on a machine that is wired to your core switch or router. Not on the laptop you are carrying.

The reason is the speed test. It measures the link between the walking device and the server. If the server is itself on Wi-Fi, every measurement crosses two wireless hops, and you are no longer measuring coverage, you are measuring the worse of two radios. Wire the host and the number means something.

Connect whatever is in your pocket

Click Connect device, scan the QR code with a phone or tablet, and the collector opens in the browser. There is nothing to install, because it is a web app. A native Android collector is in progress, but the browser is enough to survey a building today.

Then tap record and walk. Cover the places people actually use, not a neat grid. The corner office, the back of the warehouse, the patio, the stairwell everyone complains about.

Optionally hand it your controller

In Settings you can point HollowMap at a UniFi or Omada controller, or tell it None.

With a controller connected, each sample gets enriched with which access point the client was associated to and what signal that AP saw. This is the difference between knowing a spot is bad and knowing which radio is failing to cover it, which is what you need before you move hardware.

With None, you still get a real coverage map, just GPS and throughput without the AP attribution. Plenty useful for a house.

Reading the result

Back on the desktop, the map shows your samples with switchable color modes for signal, speed, and humidity. Signal and speed disagree more often than you would expect, and the disagreement is the interesting part.

Strong signal with poor throughput usually means contention or interference rather than distance. You are in range of an AP that is busy, or on a channel someone else is also using. Moving an AP closer will not fix it.

Weak signal with poor throughput is the honest dead spot. That is a coverage problem, and it responds to moving or adding hardware.

Strong everywhere except one wall is almost always construction. Old plaster with wire lath, foil-backed insulation, a fire door, a tiled bathroom. The map will show you a hard edge that does not match your floor plan, and the edge is the wall.

Then move something and walk it again

The survey is only worth what you do with it. Reposition an AP, adjust a channel, or add one where the map is empty, then record a second pass and compare.

Walking twice is what turns a coverage map into a fix. It is also the part everybody skips.

HollowMap is free for Windows. If you own a building with a Wi-Fi complaint in it, an hour of walking will tell you more than another afternoon of guessing.