# Detecting a persons position in a small room on a XY-plane (2d)

Hi guys!

Iam new to proximity applications with Arduino. I need to figure out a persons position in a rather small room (2,5m *1,5m).

Can you give me some advice on which sensors I could use? So the goal is to approximate where the person stands in that room with a presition of +-5cm. Dependent of the position arduino is going to trigger different actions. I also would like to calculate the direction and the speed of the person... (How quick can he be.. its only a small room)

I though about using 4 ultra-sonic sensors in all for corners of the room to calculate the position. Is that a realistic option? A problem that I could think of with that method is interference of the sensors? And also the question what happens if more people are in the room...

Thanks so much for your Ideas!

Cheers Niko!

Sounds like a prison cell.

This project is probably not doable with an Arduino, but let’s think through just a few of the difficulties.

First, you need to define what you mean by a person’s position. Do you mean the center of mass? What about different standing/sitting/prone positions? Does it matter if the arms or legs are extended? Then, according to your definition, how many measurements are required to determine a person’s position? How does movement figure in? If a leg is extended, according to your definition, has that person moved? Then, you raise the issue of more than one person!

@jremington:

Ah thanks man, yes my description was actually pretty sh**y, soory. Its going to be a lot easier. The gesture / position of arms/ legs etc. is not important. If you immagine a the floor as an XY-plane then I want to be able to determine the position of a upright standing person (idealy arms close to the body and legs side by side). So it.s really more about the position of someone in a 2d plane.

I though about using 4 ultra sonics in each corner at a known angle so i could "scan" the whole room and calculate the xy position out of the for returning voltages (distances). My problem here is that i fear that the 4 ultra sonics will interfer with each other. Or are they all running at slightly different frequencies? I never used them so I dont really know how they work.

Cheers Niko

Ultrasonic rangers would have a hard time in a space like that. They would interfere with each other, so would have to be operated sequentially. Reflections from walls would be a problem. Even if working properly, they return the distance to nearest object, which could be a hand.

How about a video camera? Can't do that on an Arduino though except maybe a Yun.

Ultrasonic rangers would have a hard time in a space like that. They would interfere with each other, so would have to be operated sequentially

That should be workable. How fast is the person moving??

The person is meant to walk around at "normal" speeds grand maximum 3km/h... I have leds mounted all over the walls and I want to switch on the rows of LEDs closest to the person. So if the person moves for and back wards the "light" is supposed to follow the person. It will be quite a big project. Iam in contact with china in the moment to acquire the LED`s and power supplys.

Microcontroller will probably be a Arduino Due though there is a pretty fancy shield for the Teensy 3.1 that would make the connection of the LED to the shield / controller pretty easy.

Doing the Ulra sonics sequentially doesnt sound to bad. I guess that the ultrasonic returns the distance to the closest objet as the wave return quicker to the receiver... so hands could be a problem. Though in the case of 4 sensors used I could calculate sort of an average so the back two sensors would measure for instance the distance to the back of the person and the front two sensors would get the hand (in case of holding the hand in front of your body) so I could middel out the two distances.

Mh.. how is that supposed to work with a camera? wouldn.t you have to do a fair bit of coding to analyse the picture in realtime?

Is there maybe any other type of sensor whicht could work? The Leds are placed within 10 cm of distance so the proximity measures should have at least the same resolution.