RC Car "Follow Me" with GPS
I already have the RC car working and the remote I hold working. Both equipped with GPS. Before I get started on my research on how to do this, I figured I'd reach out to see if it's already been done (likely) and if you guys could point me in the right direction?
Thank you!
If you wish it to follow you to an accuracy within about 15 metres of where you are, that may be doable. 
That is acceptable.
may even go upto 100metres depending on the location and number of available satellites.
If you describe the actual project, where the RC cars are, their size, speed etc, you might get better answers.
I thought there are already products/prototypes that will not track you via GPS but through the transmitter you are holding (as if they are able to tell the location the signal come from)
since you are likely talking about having the car beside you (within 3 meters)
Is that beacon technology? I've looked into this and found that it was a dead end because I could only find bluetooth beacon technology which is short range. I need long range. The RC might be several hundred feet away and I want to have it come to me within maybe 50-100 feet.
Oh. In that case just use both!
That's not too difficult, right?
I mean, it could be "annoying" and "time consuming" to figure out both protocols, but you can always "be lazy" and only do, for example, the GPS-based one.
I don't know. I think .. ah yes. It was DJI.
DJI drones (at least some of it) have a special mode called "follow me", where the user can put the drone anywhere in the sky (relative to their own position), click/activate this button/mode, and the drone will try to keep the relative coordinates it has with the user.
It even senses the user's heading (rotation) and will fly around in a circle/arc to match the view.
How does it work? Well, I think at least the drone have precision GPS positioning (as well as baro and other things) since it can hover and keep altitude in the wind (by itself). Then it needs to know the absolute location of the controller (which can be done by sensing the controller via beacon technology and then requesting heading/direction info from the controller over 2.4GHz wireless)
Hm. WiFi runs on 2.4GHz too. Why can't we have a 2Km WiFi signal?
Or it could be that the controller also has precision GPS positioning (and a compass), which to me sound massive overkill. It probably don't.
Wow. That's a very clever system that DJI pulled off. Not surprising given that their flight controller literally is able to fly on its own. It even remembers the path it went. Their own drones even have distance sensors pointing in 6 directions so when it flies itself (return to launch site/"home", for example), it will not just head into a tree and allows much higher precision indoors. Since you don't have a drone that can crash any second, its much easier on the 2.4GHz transmitter channel, so much so that it allows sending irrelevant info like controller heading.
The DJI "follow me" uses GPS tracking.
How come does your GPS only have 15m accuracy? How does DJI's drone (and in fact, even CC3D drones) hover in place like it is on the land?
I don't know. We used the m8n link, which is a UBX-M8030. You can interface the module with a regular microcontroller (like all drone controllers are), or get the standalone chip and build your own thing around it.
We used an older version with Pixhawk 3.2. It really does well.
It uses UART for GPS and I2C for the compass.
Who said that?
The M8N SE100 have accuracy down to 50cm (dual band), and a low-end Ublox claims "<2m"
Drone GPS is only so accurate because they do not have the privilege to use military channels, which have accuracy down to centimeter
Man, I want one of those now just to mess around. Although, have my coord at all times doesnt seem to be very useful. Better off with a $300 3-axis gyro + accelerometer combo.
Choose the radio link with care. If the ground the RC cars are on has any type of vegitation than some radios, such as NRF24s might struggle to cover the distance.
But I have no idea how far 'several hundred feet' is.
If he is using any aftermarket 2.4GHz RC grade transmitter/receiver (that can do 2Km if it have line of sight), in an "urban" mixed environment with buildings, cars and other obstructions it can do at least a few hundred meters. A thousand feet, let's say.
Plus, if you are indeed 500 feet away (152 meters), you might not be able to see the car at all. In that case establishing a good 2.4GHz link is useless and GPS will be able to guide you.
Sure, there are radios that can do what the OP wants.
As its an Arduino forum I sort of assumed to answer the question in relation to typical Arduino used radios. The NRF24 is the often suggeted one, but might not be good enough for the distance.
I am not sure what the commercial units (e.g. my T8FB) uses. Chances are they custom-built them because you would consider the various different protocols they use (and how the fact that all the different brands don't recognize the signals from other brands)
It is entirely possible to create a similar performant device/solution. All of those are microcontrollers (with a bit of additional circuit), after all. It's a matter of time spent smashing the keyboard up as you implement the many different things that a commercially available unit does. Or use a total of 20 libraries from 50 different people and suffer from the lack of performance/size/interoperability of them.
I cannot identify the chip Radiolink used on the T8FB because they didn't use one. They used epoxy or some sort and just "gooped" a drop on to the controller silicon (that are electrically connected to the board with tiny wires), but even if there is a chip its likely either a Radio-focused microcontroller or a Radiolink special.
It's not necessary to re-invent the wheel. Unless it doesn't exist.
There are many radios I guess like the RFM69 (modules from HopeRF) ,CC1101,CC1120, HC-12 etc which can do upto 100 metres easily, not sure about the bit-rate he wants. Even Lora modules can be used as they can very easily send beacons to kilometres range. To avoid interference in the 2.4GHz band, the best and easiest way is to not use that band and use other bands like 433,868,915MHz (subjetc to local laws) etc.
In Land, there are many obstructions, so GNSS is necessary to navigate properly to destination. Maybe something like Google Maps direction integration (if that is possible, Idk) can help...
Hey guys I'm using this radio. I was not aware that some radios can track position as well? Is this some sort of beacon technology?
Whatever makes you think they can? 
Neither was I.
Most radios are just that radios, to track position you need to add stuff such as a GPS.
There is a LoRa module that can measure the distance between transmitter and receiver.
Good choice.
It cannot track position. With some clever tricks (that might involve two of these receivers angled at different positions) maybe you can get a notion of where the signal come from, but you are much better off just using two GPS modules.
The lower the frequency, the easier it is to travel through ... stuff just as adafruit mentioned. The exact frequency you can use depend on your local regulation.
One Idea just caught my mind, can we use Echolocation (of Radiowaves) to get the approx distance of the receiver? I assume RF waves travels at speed of light and we can use the same method as we use in calculating distance in HC-SR04...
Yes; been possible for a while (Ranging == DistanceMeasuring) ;