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What methods exist to track the position of points relative to each other. Particularly what methods allow the determination of the distance between up to ten points at once. The distance determination needs to be wireless and should be able to work thru someones arm. This all needs to able to be wired up to a raspberry pi two or arduino. The measurements must be able to take place in in a few milliseconds and repeat constantly. The resolution does not have to be very good about 2 millimeters would work. All of the 10 points can be powered by wires attaching it to the micro computer. Everything will be attached to the arm by tape.

I have looked into both magnetic and RFID solutions, but I don't know enough about either to know if they would work.

user
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  • What does ~0“-6” mean? – Andy aka Jan 09 '16 at 19:13
  • @user, welcome to StackExchange. The quality of the answer to your question will, to a large extent, depend on the quality of your question. Read it again and ask yourself how anyone could answer it. Points have no mass, no dimensions and are invisible. They are undetectable. Presumably you mean something else. Tell us the application and where and what the points are. – Transistor Jan 09 '16 at 19:19
  • See the answers to https://electronics.stackexchange.com/questions/33110/options-for-short-range-distance-determination-between-two-objects?rq=1 - the magnetic coil approach is often used for precision tablet pens. Or you could do it visually like the Leap Motion. – pjc50 Jan 09 '16 at 19:33
  • @Andyaka aka around zero to six inches. – user Jan 09 '16 at 19:38
  • @transistor Obviously a idem like a RFID tag or a magnet will have to be on the points. I mean point just how you defined it. – user Jan 09 '16 at 19:46
  • @pjc50 The measurements must take place constantly in close to real time. – user Jan 09 '16 at 19:50
  • @user, it's not obvious to us what you have considered so add methods you've though of into your original question. You might also explain whether these are attached to the skin, whether they can be powered devices and what accuracy / resolution you require. Are you tracking absolute position or relative position, etc. – Transistor Jan 09 '16 at 20:00
  • @user: Good information. Another question: is the patient hold the arm in the air or can it lie in an arm-holder or tube (which might, for example, also hold the monitoring electronics)? Again, pop the additional info into the question. – Transistor Jan 09 '16 at 20:16
  • @transistor the arm has to be out and mobile. The sensors will be taped to the persons arm. – user Jan 09 '16 at 21:03
  • Can you connect the sensors to each other with rods, or wires or threads under tension? –  Jan 09 '16 at 22:39
  • @BrianDrummond like I said the distance determination needs to be wireless but they will all be connected the same micro computer. – user Jan 09 '16 at 22:45
  • I'm pretty sure your options are : cameras in 3 axes. And some software that I'm not going to volunteer to write! –  Jan 09 '16 at 22:52
  • @BrianDrummond I it needed to be self contained no cameras. Theoretically magnetic measurement could do it. But I don't have any experience with that. – user Jan 09 '16 at 22:57
  • yeah, in theory magnetic could do it. measure the magnetic coupling between each point and all the others, solve for orientation, and then compute distance, RPi can probably handle the arithmetic, but you'll need to add some DACS and ADCs. – Jasen Слава Україні Jan 10 '16 at 04:43
  • are you trying to track the position of the fingertips on both hands? – user96635 Jan 10 '16 at 07:37
  • I have two uses one measuring the position of a arm the other measuring position of fingertips on one hand. – user Jan 10 '16 at 07:48
  • @user: What's your budget? Add this information to the question. – Transistor Jan 10 '16 at 16:33

1 Answers1

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2 Cameras are the easiest solution. AFAIK, the Pi includes a camera input. RFID will have too high latency (The time required to read each RFID chip), and its location accuracy will be very dependent on the environment.

If you can provide power to the sensed elements, adding LED to the element and synchronizing them to the main MCU and detectors will make your job much easier, cause you will not have to do outline detection and complex image processing in real time (aka Microsoft's Kinect).

Lior Bilia
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