You can opt for watches if you are looking for a wearable. Garmin is one of the most reliable brands that relies on GPS technology rather than solely Bluetooth tech. with its limited range. People like to use these because they can fasten them to something to keep them in place. You can also use tags to stick to someone’s belongings to track people, however, please remember to choose a tag/device that uses GPS technology not Bluetooth technology if you aim to track outside the vicinity of your home. Bay Alarm and Garmin are popular brands that get quality reviews from users. Buddy Tag and Tile are also reliable, however, they are Bluetooth trackers which means they are limited to a 80 to 120 feet range though.
It is sometimes incorrectly said that the user location is at the intersection of three spheres. While simpler to visualize, this is only the case if the receiver has a clock synchronized with the satellite clocks (., the receiver measures true ranges to the satellites rather than range differences). There are significant performance benefits to the user carrying a clock synchronized with the satellites. Foremost is that only three satellites are needed to compute a position solution. If this were part of the GPS system concept so that all users needed to carry a synchronized clock, then a smaller number of satellites could be deployed. However, the cost and complexity of the user equipment would increase significantly.