Knowing where you are is a fundamental need for humans, one that advanced greatly over the course of the twentieth century, when it was transformed from taking sights using a sextant to the satellite-based Global Positioning System, GPS. Growth of the internet, its early commercialisation, and the introduction of mobile devices combined in the early twenty-first century with the first location-based services. Navizon, one of the pioneers, was founded in 2005 to develop services able to determine location of mobile devices without a GPS receiver, or as an enhancement to GPS.

When the first iPhone was launched in 2007, it came without GPS, but the second model, the iPhone 3G of the following year, featured assisted GPS, using additional location data to improve the accuracy of that from its GPS receiver. By 2011, the iPhone 4S came with assisted GPS, GLONASS and a digital compass, and iBeacon support was added in 2014 with the iPhone 6.

By comparison, Macs have never incorporated a GPS receiver, nor cellular modems, yet their location can still be determined fairly accurately, as Google and other services are fond of reminding us. Apple introduced its first Find My iPhone service in June 2009, based on a MobileMe subscription, and that became free and extended to Mac OS X Lion when iCloud replaced MobileMe in 2011.

IP address

Earliest work on the location of computers connected to the internet was based on their internet IP address, that assigned to the router to which they connect. Those are allocated in blocks, and for service providers with limited geographical coverage can be used to narrow location down to small catchment areas. On their own, though, in some cases they can’t even determine country.

Several commercial services have developed private databases that can resolve most internet IP addresses to towns and smaller districts, although in some cases errors can be large. They’re also susceptible to false information with the use of a VPN or proxy service, as demonstrated by the Private Relay service included in Apple’s iCloud+.

Wi-Fi signals

Apple introduced AirPort Wi-Fi internet connection in 1999, and its use rapidly became popular during the first decade of this century. Wireless access points were soon installed in many public locations, and Macs and Apple’s devices have been able to identify those nearby by their Service Set Identifier (SSID) and MAC address.

Provided the location of several nearby Wi-Fi access points is known, and their signal strengths can be measured as their RSSI (received signal strength indicator), it’s not difficult to estimate a fairly precise location of a computer equipped with a Wi-Fi interface. Median precision for this technique can be as low as 2-4 metres (6.5-13 feet), and more advanced methods can achieve even better. Unlike GPS, which requires a clear view of each satellite used for a ‘fix’, Wi-Fi signals can be just as effective indoors.

Several major databases have been compiled, some containing data for more than two billion Wi-Fi networks. Most are proprietary and operated as commercial services.

Wi-Fi is now the mainstay of Location Services for Macs, and one of the benefits of enabling a Mac’s Wi-Fi even though it may also have wired Ethernet connections. It’s also the reason that Location Services aren’t available to macOS virtual machines running on Apple silicon Macs, as they don’t support suitable access to the host Wi-Fi, even though they can use that for their network connection.

iBeacons and others

At the same time that Wi-Fi was being introduced, Bluetooth wireless connections were rapidly becoming universal. The first Bluetooth device, a hands-free headset, was revealed in 1999, and Apple added support to Mac OS X 10.2 three years later. In 2019, macOS Catalina introduced iBeacons, Bluetooth Low Energy transmitters that can be used by Macs and Apple’s devices to measure their proximity. These can determine precise locality within buildings where Wi-Fi isn’t suitable.

Although I’m not aware of any documentation, now that devices like iPhones with their more extensive location hardware are commonly used together with Macs, it’s feasible that Macs could supplement their own location methods with data supplied by a connected device. Third-party GPS receivers and cellular modems can also be connected to Macs, but they don’t appear to enjoy support from macOS, and can’t contribute to a Mac’s location information.