Sensor for Accurate Tracking

So, I am currently trying to figure out what sensors would work best for my Arduino project. hHowever, I am having trouble and am hoping someone on here might have the answer.

The question is...

Say i have a 100 m by 100 m square. I want to track one person in that square and have an autonomous device on the edge of that square use motors to follow their position.

I am not opposed to the person wearing something to aid in the tracking. I'd like the tracking to be very accurate (within cm), able to track in live time and able to track the person if they're moving quickly. Power consumption is not that big of an issue as it could plug in if necessary.

What I've looked at so far...

  • GPS - Doesn't seem to be accurate enough 5-10 ft off.
  • Bluetooth - Not sure how to track just using a bluetooth signal. Does reach up to 100 m depending on the sensors.
  • Range finder - Not enough distance (without paying a lot of money it seems like).
  • Ultrasonic - Not enough distance.
  • Lidar Lite - Could use this but it may get expensive if I need more than one to track the person.

Any suggestions would be very helpful!

Thanks!

Lidarlite on a servo head that you pan back & forth.
You know the angle it is turned, you have a distance, do the math.
A reading of more than 100m indicate no return.
"easy-to-use 40-meter laser-based optical ranging sensor"
Course, that could be a problem if "100m" means 100 meters.

Golf range finders have really long range, several hundred yards, accuracy to 0.1 of yard. You should look into that tech some more. I don't know of any with a serial output.

So basically you have a flat empty square, and two robots on two of the sides. One following the X coordinate of the person, the other following the Y coordinate, right?

Have the person wear a beacon (e.g. a modulated IR beacon - has to be omnidirectional and pretty bright), then put a radar-like sweeping device on each robot that basically rotates 180 degrees front to back, finds the direction of the beacon, then positions itself where the beacon is at 90 degrees.

You don't even have to know the actual coordinates, just need some way for the robot to move forward/backward and stay on track (use a line following ability, or rails for it to roll on, or whatever works for you).

For added fun, add a flashing red light to the beacon the person wears. It's not doing anything to help the robots but for sure it will look cool.

GPS is only accurate to 5-10 ft in absolute accuracy. But two GPS receivers near each other get about the same inaccuracies. So the differential between to receivers 100m apart will be much smaller than this. I should think it's possible to get to centimeter accuracy with no special effort.

When playing a lot with GPS devices a few years ago (I don't do much geocaching these days) it was quite normal to have a bunch of devices that all pointed to a different point in a 3-4 meter radius from one another. Maybe better than the individually reported errors, still nowhere near cm accuracy.

I appreciate the responses I'm still just not sure how to tackle this issue yet though...

You can certainly buy cm-accurate GPS units. Last I checked most prices were still in the several thousand USD range, plus you have to be near a reference station and pay for the service subscription.