Sorry, 99% of the elderly and children locators on the market may be a waste of money.

Have you ever seen a T-shirt like this?

In Xuancheng, Anhui Province in 2022, a granddaughter customized a T-shirt for an elderly person.

Behind this T-shirt lies the most simple concern of a family: fear of their loved ones getting lost and not being able to find their way home.

This kind of concern is not an isolated case. According to the data from the "White Paper on Missing Persons in China" in 2020, up to 1 million people go missing across the country every year, with an average of about 1,370 elderly people getting lost every day.

Getting lost is terrifying. It's even more terrifying when the elderly or children get lost - they can't clearly describe their location and can't find their way home.

This widespread anxiety has given rise to a huge market. You'll see that various children's smartwatches emphasize their positioning functions and the ability to track movement trajectories. On Taobao, elderly person locators can easily sell thousands or even hundreds of thousands of units.

Search results for elderly person locators on Taobao

Facing these devices with different appearances, functions, and prices, a core question confronts every family: What kind of locator is the most effective?

To answer this question, we first need to understand the technological secrets hidden in these products.

Locators on the market mainly rely on the combination of the following technologies.

Guidance from Space - Navigation Satellite Positioning

This is the most common and familiar way. Whether it's car navigation or mobile phone clock - in, it can't do without it. Navigation satellites, including China's Beidou and the US's GPS, are actually doing a very simple thing: they continuously broadcast their current precise time to the ground from space.

Beidou - 3 navigation satellites in geosynchronous orbit | Wikipedia

After your positioning device receives signals from at least 4 satellites, by calculating the tiny differences in the arrival times of these signals, it can deduce its own longitude, latitude, and altitude.

Advantages: It has a wide coverage area and is the basis for all outdoor positioning.

Disadvantages: The signal is "a bit fragile". In the civilian field, its best accuracy can only reach the meter - level. Once in a city with high - rise buildings, the satellite signals are blocked and reflected by buildings, and the accuracy will further drop to more than 10 meters. This is why our navigation sometimes "drifts" in the city. Moreover, it can hardly be used indoors.

Inaccurate positioning may also be the fault of the city | Giphy

"Lighthouses" in the City - Base Station and WLAN Positioning

When satellites "can't see" us, the locator will activate a backup plan: look for signals around us, such as mobile phone base stations and Wi - Fi hotspots.

The closer you are to the router, the stronger the signal | Giphy

The service provider's database records the geographical locations of countless base stations and public Wi - Fi routers. Each base station is like a lighthouse. The closer you are to it, the stronger the signal.

As long as your device can detect these signals, it can roughly estimate which "lighthouse" you are closer to and which one you are farther from according to the signal strength, and thus determine the approximate area where you are located.

By the way, this has nothing to do with whether you know the Wi - Fi password. As long as the signal can be detected.

Base station positioning, abbreviated as LBS | uffizio

Advantages: It perfectly compensates for the shortcoming that satellite positioning cannot cover indoor areas. As long as there is a mobile phone signal, base station positioning (LBS) can be useful, and its application scope is extremely wide.

Disadvantages: The accuracy is not high. In urban areas with dense base stations and Wi - Fi, the accuracy is about 5 to 15 meters. If you go to the suburbs where there is only one base station nearby, the positioning error may expand to hundreds or even thousands of meters.

The positioning beacons on wild animals use dual positioning of base stations and satellites to track trajectories | University College Dublin

The Power of the Masses - Bluetooth Device Network

To achieve high - precision indoor positioning, another common choice is Bluetooth. The premise is that you need to install beacons - small devices that continuously emit Bluetooth signals, and then send out the precise coordinates of the beacons.

In museums or shops, Bluetooth beacons can help people quickly find what they want to see, with an accuracy of 2 to 5 meters.

But we can't expect the whole world to be covered with beacons. So, a clever idea was born: Make every mobile phone a mobile beacon.

Apple's AirTag | Apple

This is the basic principle of device networks such as Apple's "Find My" and Huawei's "NearLink". When an AirTag or Huawei Tag is marked as "lost" by its owner, it will continuously emit an encrypted Bluetooth signal. Any stranger whose Apple or Huawei device passes by will, as if "helping out casually", capture this signal and anonymously upload its location information to the network, allowing the owner to see it.

NearLink Find can also locate in this way | Huawei

Advantages: It creatively constructs a huge lost - item search network and solves the core problem of the small range of Bluetooth positioning.

Disadvantages: Its effectiveness completely depends on the density of devices of the same brand in the surrounding area. In sparsely populated areas, the effect will be greatly reduced. Moreover, its accuracy is still limited and can only help you narrow down the range, unable to achieve precise pointing.

The inductive unlocking of many electric bicycles is also achieved with Bluetooth beacons | Lenz Technology

The Ultimate Weapon - UWB Precise Positioning

By comprehensively using satellites, base stations, Wi - Fi, and Bluetooth, we can usually locate our lost family members in a community, a building, or a shopping mall. But the real challenge is just beginning.

Many people have had this frustrating experience: the mobile phone map shows that the target is right at this point, but you walk around for several circles and still can't find the person. For anxious family members, the "last fifty meters" is often more torturous than not knowing the location at all.

This is when UWB technology comes into play. It is currently the best solution to the "last fifty meters" problem in the civilian field.

You may have first heard of it because of Apple's AirTag. Its full name is "Ultra - Wideband". As the name suggests, the electromagnetic wave frequency band it emits is very, very wide, but the emission time each time is very short. In theory, it can emit once every 2 nanoseconds. Since the power at each frequency can even be lower than electromagnetic noise, it is very difficult to be monitored, so it has high security.

The orange line represents the UWB range, which is very wide | Murata

Each positioning device that emits electromagnetic waves is like a flashlight flashing crazily. The faster the light flashes, the higher the measurement accuracy.

How fast can the electromagnetic waves of the UWB mobile phones, watches, and keychains we can buy flash?

Taking the AirTag as an example, it can flash once every 8 nanoseconds at the fastest, which is equivalent to flashing 125 million times per second. Of course, this is only a theoretical value. Generally, its working frequency will be lower to save power.

The faster it flashes, the higher the positioning accuracy | Giphy

It is precisely with this ultra - high - frequency pulse signal and the ultra - wide frequency band with strong anti - interference ability that UWB can achieve centimeter - level positioning accuracy.

If the device has two antennas, it can even calculate the precise direction of the target through the order of signal arrival. At this time, there will no longer be a blurry light spot on your mobile phone, but a clear arrow telling you "Walk 6 meters to the front - right".

UWB positioning can also indicate a specific direction | Apple

The advantages and disadvantages of UWB technology are also very prominent:

Advantages: It has extremely high accuracy, reaching the centimeter - level, and can indicate a clear direction. This makes it extremely effective when looking for items that are close - range and blocked (such as keys under the sofa cushion), or when solving the "last fifty meters" problem in complex environments such as crowded areas or densely - built buildings. At the same time, devices equipped with UWB (such as positioning tags) are usually small in size and have long battery life.

Disadvantages: UWB itself is a short - range positioning technology and cannot independently complete long - distance tracking.

So, what should we buy?

After understanding the underlying technical principles, when we look back at the diverse products on the market, our thinking becomes much clearer.

Smartwatches/bracelets: These products mainly rely on navigation satellites, base stations, and WLAN for positioning. Their greatest advantage is that they are convenient to wear and can have two - way calls. In the early stage of a family member getting lost, a phone call can often solve most problems. However, these devices consume power quickly, and the battery life ranges from one day to one month. Once the power runs out and the device shuts down, the location information is completely lost.

Anti - loss positioning keychains: Represented by Apple's AirTag, Samsung's SmartTag +, etc. Their strength lies in using Bluetooth to form a network with devices of the same brand for tracking. More importantly, many of these models are equipped with UWB technology, which can solve the "last fifty meters" problem and achieve centimeter - level accuracy in searching. At the same time, they are small in size, and a single battery can last for a year. The disadvantage is that they cannot make calls and can only perform one - way tracking.

Other devices: There are also positioning shoes, positioning schoolbags, etc. on the market. Although these products are concealed, they often have problems such as not being washable, difficult to charge or replace the battery. As for mobile phones, they have the most complete functions, but for the elderly who are not used to carrying them or may forget to charge them,