By default, NetSpot shows the entire range of measurable signal for the signal and noise visualizations, but you can choose a higher minimum and/or a lower maximum. For example, if you want to ensure that you have at least a certain SNR (which essentially means that the network can operate at or above your desired minimum speed), you could set that SNR as the minimum; anything below that minimum simply won't appear on NetSpot's map. Figuring out such a threshold, however, is beyond the scope of this review. NetSpot could improve on this feature by adding bandwidth tests that would allow some educated guesses about the typical range of Wi-Fi speeds at a given spot.
The map also identifies the rough position of each base station. I was stunned by how well it performed this task in my home. I have three base stations, one on our main floor, and the other two at opposite ends of the basement; while walking the main floor, NetSpot placed the basement and upstairs AirPort routers within a foot of their actual positions by triangulating signal-strength measurements. If an estimated placement is incorrect, NetSpot offers a slider for adjusting the signal threshold at which an access point is thought to be detected. However, pushing the value higher may cause some access points to disappear--to avoid that, drop a pin during your survey phase as physically close to each base station as possible. (Unfortunately, you can't manually designate, on the map, the precise location of a base station.) Click any base station on the map to get detailed information about it and its offerings.
NetSpot's map initially displays only signal information for base stations on the network to which your Mac is currently connected (assuming you're connected to one), as well for the base stations of nearby open networks. But the utility gathers information for every other router it finds, as well, and you can choose precisely what's displayed. NetSpot is able to track separately the 2.4GHz and 5GHz networks created by simultaneous dual-band routers, such as 2009 and later AirPort Extreme and Time Capsule models.
The Detected Wi-Fi Networks list on the left side of the main window lets you choose whether or not each router's readings are integrated into your map. A Configure pop-up menu below that list allows you to choose routers by channel, which can be helpful in choosing an unused Wi-Fi spectrum if you're in a crowded network environment, such as in an urban apartment or condo.
If you have multiple networks of your own, or have access to multiple nearby networks--some people live above a Starbucks--you can see how these networks fare individually or together. You can also click any point on the map and get a list of all the selected base stations and their corresponding visualization data (such as the SNR or quantity of base stations at that point), interpolated from the points at which you took scans.