AirMagnet Surveyor reviewed

| Wireless Driver & Software

Doing the Survey

Allrighty then! With all the preliminaries out of the way, we can now start the survey. Surveyor uses a simple, but effective way for the user to communicate the path taken during the survey. You simply estimate where you are on the Site Map, move your mouse pointer and click to mark the spot. Figure 8 shows what this ends up looking like after a survey walk.

Figure 8: Site Map plus Survey Path
(click on the image for a larger view)

Each of the slightly larger red square dots indicates a clicked (entered) location point while each smaller blue square dot represents a location where Surveyor calculated that a signal data sample was taken.

Though this seemed simple enough to start, it wasn’t long before I starting wondering how often I was supposed to indicate my position. The printed User Guide was no help, saying only “Click on the map accurately where you are as you walk”. It turns out that the key to knowing how often and where to click lies in understanding how Surveyor marries the Site Map location clicks and signal data samples.

Because Surveyor has no innate way of knowing where each data sample was made, it relies on the user to accurately click his / her location on the Site Map as the survey progresses. Surveyor then uses that information, along with a time stamp for each data sample, to estimate where each sample was actually taken and attach calculated X and Y coordinates to each sample.

Since the calculation is done using a straight line interpolation, it’s important that you click just before each change in direction and estimate your location as accurately as possible. An example will show how important it is to watch where you click!

Let’s say I start a survey by clicking my start location on the Site Map and I’m using the default data logging rate of 3 seconds between samples. Right after I click, I drop my favorite pen and spend about 10 seconds finding and picking it up. Pen retrieved, I now move 20 feet down the hallway and click to indicate my location. If I stopped the survey at this point, Surveyor would show a survey path something like Figure 9.

Figure 9: Misleading Survey Path

Note that Surveyor has taken the three data points that were actually taken at the same location while I was hunting for my pen and distributed them evenly along a 20 foot path. This is obviously incorrect – the correct diagram would show three data samples clustered near the starting point – but accurate according to the location information I gave Surveyor.

What I should have done is either click again on the survey start point before I began to move, paused the survey (using Surveyor’s Pause feature) right after I dropped my pen, or just restarted the survey after clearing out the incorrect data. If you end up in a blind alley, or just decide that you don’t want data you gathered along a particular survey leg, you can also use Surveyor’s Retract function to erase the most recent path.

Surveyor lets you perform two survey types. A “passive” survey gathers signal, noise channel and SSID data from all in-range APs – much like AirMagnet’s Laptop and Handheld products. You can also perform “active” surveys that log signal info from a specific AP that you choose to associate with or multiple APs in a specified SSID. The setup for both survey types is pretty much the same with the “active” survey only requiring you to choose an SSID or AP to associate with.