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point to point distance tracking in a room

Posted: Mon Feb 09, 2015 2:18 pm
by basiel
Hi there,
I am woking on a project where i want to measure the distance between 2 points in the room (through X,Y,Z coordinates).
There is a fixed startpoint, this point will always be the same (can be seen as origin, X=0, Y=0, Z=0).
It needs to have an accuracy of about +/- 10 cm.
It will be indoors so i don't know if GPS will be accurate enough ?
Thanks in advance,
Basiel

Re: point to point distance tracking in a room

Posted: Mon Feb 09, 2015 9:25 pm
by morphy_richards
I dont think GPS works very well at all indoors. (Unless you have a glass roof or very very big windows on 2 walls :? )

Could you perhaps use something like three Sharp IR Range sensors at 90 degrees to each other? (and an I2C ADC) They would report distance to wall1, wall2 and floor? Should be easy then to convert those distances to X, Y, Z.

... Or 3 sonar range finders , easier to use...

Re: point to point distance tracking in a room

Posted: Thu Feb 12, 2015 7:26 pm
by basiel
Okay , thank you i will do research regarding these tips ! :)

Re: point to point distance tracking in a room

Posted: Thu Feb 12, 2015 7:33 pm
by mikerr
morphy_richards wrote:... Or 3 sonar range finders , easier to use...
You might get interesting results if one receives the other's echo...

Re: point to point distance tracking in a room

Posted: Fri Feb 13, 2015 12:02 am
by DougieLawson
mikerr wrote:
morphy_richards wrote:... Or 3 sonar range finders , easier to use...
You might get interesting results if one receives the other's echo...
Beyond about a metre you need a very smooth reflective surface to get a range, those things don't shout very loudly.

Re: point to point distance tracking in a room

Posted: Fri Feb 13, 2015 7:07 am
by morphy_richards

You might get interesting results if one receives the other's echo..
I suppose they can always take turns.

Re: point to point distance tracking in a room

Posted: Fri Feb 13, 2015 7:38 am
by jimallyn
GPS won't be accurate enough, inside or out. My GPS receiver shows the error margin, and I think the best I've ever seen is +/- 9 feet. That's outside with good signals. I understand GPS can provide better accuracy than that, but unless you have a high end GPS intended for surveying or the military, you're not likely to get very good results.

Re: point to point distance tracking in a room

Posted: Fri Feb 13, 2015 8:54 am
by bantammenace2012
How about using The Rsapberry Pi camera to take a photo of a table tennis ball or similar spherical object at the point you wish to measure to ? Using OpenCV and knowing the diameter of the sphere it is likely to be possible to compute the distance required. If you don't need it "real-time" all you really need to know is the number of pixels across the diameter of the sphere and then using a look up table based on observations at known distances you can compute the known distance. This is simple photogrammetry.
I am looking to use this method to measure the distance of the moon's perigee. it won't require a full moon just a knowledge of the moon's diameter.

Re: point to point distance tracking in a room

Posted: Fri Feb 13, 2015 9:27 am
by PiGraham
basiel wrote:Hi there,
I am woking on a project where i want to measure the distance between 2 points in the room (through X,Y,Z coordinates).
There is a fixed startpoint, this point will always be the same (can be seen as origin, X=0, Y=0, Z=0).
It needs to have an accuracy of about +/- 10 cm.
It will be indoors so i don't know if GPS will be accurate enough ?
Thanks in advance,
Basiel
Can the points be anywhere in the room (x,y,x)? How big is the volume in which you want to measure?

What are the points? Are they visible objects?

Camera tracking is an option, if you can see the points.

Some form of sonar could work.

There are some cheap(ish) LIDAR sensors (Search Sparkfun)

Servo tracking opto detectors and triangulation could work.

How fast should the measurement be? Are the points moving?

The more info you can give the better the chance of getting an answer that will fit.