Tracking movement.

[Climber]

Hi Guys / Girls.

I've been lurking for ages and finally got round to signing up as I think this may be the only place I can find on the internet with knowledge that's varied and obscure enough to answer my question.

What i'm looking for isn't exactly easy to explain, which i think is why Google is being little use.

Basically, I'm trying to find a 'gadget' that can be used to very accurately track positions in relation to either each other, or a fixed point. Apparently GPS is nowhere near accurate enough for this. I need to be plus or minus a mm at most. The individual points will be no more than a few meters apart. I also need to log the movements for a set time period, and have some way of representing the movement somehow on paper.

To give a bit more of an idea of what i'm trying to achieve, imagine attaching sensors to each piece of washing on a washing line, so that the movement of each piece could be logged in relation to the line, and then the data could be used to create some kind of graphic or even artistic representation of the movement.

Anyone understand a word I've said? Apologies for the lack of clarity, it's currently just an idea in my head, whirring around trying to make sense of itself.

 

[Mattuk]

Would laser tracking work for you ?

https://www.qualitydigest.com/inside/metrology-article/how-laser-trackers-work-062509.html

 

[Tinbasherdan]

You’d be looking at something similar to what they use to map movement for CGI I would imagine, not very cheap!

 

[Climber]

Would laser tracking work for you ?

https://www.qualitydigest.com/inside/metrology-article/how-laser-trackers-work-062509.html

To be honest, I'm not sure. I'm thinking probably not, as I would presume lasers would need constant line of sight. For the application i'm considering, that may not be possible.

 

[Climber]

You’d be looking at something similar to what they use to map movement for CGI I would imagine, not very cheap!

Yep, that makes sense. I was also thinking of the sensors that track movement for virtual reality, or even how a Nintendo Wii knows where the controllers are. I'm sure the technology exists, I'm just lacking any kind of technical knowledge, so I don't really know what I'm looking for.

 

[voipio]

If constant line of sight is not guaranteed then all optical methods are likely to be a non-starter. That leaves using sound (probably ultrasound) and RF, but ulltrasound also needs line of "sight" or hearing, and RF can be deflected/reflected or passes through, depending on the materials used, the environment, and the frequency employed. The Wii uses accelerometers and algorithms, but drift in estimated position will be an issue.

 

[Climber]

If constant line of sight is not guaranteed then all optical methods are likely to be a non-starter. That leaves using sound (probably ultrasound) and RF, but ulltrasound also needs line of "sight" or hearing, and RF can be deflected/reflected or passes through, depending on the materials used, the environment, and the frequency employed. The Wii uses accelerometers and algorithms, but drift in estimated position will be an issue.

Thanks. I've just found this. Would that suffer from any of the limitations you mention?

 

[voipio]

The accelerometers and gyroscopes in the Orientus device, referred to in the link, have an "instability" specification e.g. gyroscopes 3 degrees per hour, accelerometers 20 micro g, plus scaling and non-linearity errors, which will stack up, plus the device needs to be wired for power and signals, and there would need to be one device attached in some way to each tracked object. It might be usable if there was constant, or at least regular reference to known points in 3D space e.g. bar code readers. Then there would be the system integration, and writing the code to use these sensors and provide meaningful output.

 

[Climber]

The accelerometers and gyroscopes in the Orientus device, referred to in the link, have an "instability" specification e.g. gyroscopes 3 degrees per hour, accelerometers 20 micro g, plus scaling and non-linearity errors, which will stack up, plus the device needs to be wired for power and signals. It might be usable if there was constant, or at least regular reference to known points in 3D space e.g. bar code readers. Then there would be the system integration, and writing the code to use these sensors and provide meaningful output.

I'm not that bothered about accuracy. I know that seems like a strange statement; what i mean is that although i need it to be able to sense quite small movements, it doesn't actually matter that much if it's not that accurate. The logging of movement generally, is a lot more important than impressive accuracy.

I get the feeling i'm just digging myself into a deeper and deeper hole. I thought I understood roughly what was required until I asked the question.

 

[hotponyshoes]

I use both an optical (high speed cameras) and accelerometer based systems for tracking and gait analysis on horses.
Both types are capable of sub 1mm accuracy in the correctly calibrated conditions.
Both types are based on the sorts of things you would use for cgi but required a fair bit of faffing about to get them to the stage of how I wanted to use them.

If you post a few more details of what you are actually doing and what objects you are trying to track we might be able to offer a bit more help,
For example the video based system can track down to one pixel so, depending on the cameras/lenses you use, could offer very precise measurement but results vary depending on what you are trying to track and the systems you are trying to track it in.
You can inject individual blood cells with a radioactive isotope and track with submicron precision using mir if you want but again, without knowing the application might be completely unsuitable for you!

 

[TechnicAl]

Hi Guys / Girls.



To give a bit more of an idea of what i'm trying to achieve, imagine attaching sensors to each piece of washing on a washing line, so that the movement of each piece could be logged in relation to the line, and then the data could be used to create some kind of graphic or even artistic representation of the movement.

Anyone understand a word I've said? Apologies for the lack of clarity, it's currently just an idea in my head, whirring around trying to make sense of itself.

Be careful you could get accused of money laundering...........sorry

 

[Climber]

I use both an optical (high speed cameras) and accelerometer based systems for tracking and gait analysis on horses.
Both types are capable of sub 1mm accuracy in the correctly calibrated conditions.
Both types are based on the sorts of things you would use for cgi but required a fair bit of faffing about to get them to the stage of how I wanted to use them.

If you post a few more details of what you are actually doing and what objects you are trying to track we might be able to offer a bit more help,
For example the video based system can track down to one pixel so, depending on the cameras/lenses you use, could offer very precise measurement but results vary depending on what you are trying to track and the systems you are trying to track it in.
You can inject individual blood cells with a radioactive isotope and track with submicron precision using mir if you want but again, without knowing the application might be completely unsuitable for you!

Thanks for your reply. I don't need anything anywhere near as technical as you describe.

Basically, as you may guess from my username, I'm an ex professional climber. What we actually want to do is investigate how things we climb move independently from each other. When climbing towers, trees, or anything that has several stems, independent motion of each 'branch' causes problems. Imagine climbing 50 feet up a flexible tower, then trying to move across to another tower. It's easy to get across, but then if the towers move apart your climbing gear tries to pull you off the tower. Equally, if the towers move together you lose all tension in your gear, which isn't the most pleasant experience either. In an effort to understand the problem (and maybe remedy it) we first want to understand in detail the movement that occurs.

Does that help at all?

 

[MattH]

Sounds like you need what they use on the railways. When doing any work near the tracks they setup a laser scanner head and place multiple small prism reflectors around the site. They then scan the position of each prism before starting any ground works. The laser head then rescans all the prisms on a cycle and any positional discrepancy’s can be logged and analysed.

Don’t know what it’s called, my uncles used to work on the railways and used them.

 

[Climber]

Sounds like you need what they use on the railways. When doing any work near the tracks they setup a laser scanner head and place multiple small prism reflectors around the site. They then scan the position of each prism before starting any ground works. The laser head then rescans all the prisms on a cycle and any positional discrepancy’s can be logged and analysed.

Don’t know what it’s called, my uncles used to work on the railways and used them.

Ideally I want the position to be logged at least once a second, if not significantly more. Also, I think the above would need line of site between the main unit and the reflectors at all times. I actually have a client who lifts houses, and they use something very similar to check the house is being lifted straight, square, and level.

 

[MattH]

I can’t see how you would achieve what you want without line of sight.

I’m sure something could be put together with an Xbox connect units and small white stickers (have a look on YouTube for hacking Xbox connect).

But it would require line of site.

 

[Climber]

I can’t see how you would achieve what you want without line of sight.

I’m sure something could be put together with an Xbox connect units and small white stickers (have a look on YouTube for hacking Xbox connect).

But it would require line of site.

Me neither, which is why i'm having a problem. In my mind, I had imagined strapping a clever box of electronic trickery to a fixed point and then another box of trickery to one of the moving objects, and then these clever boxes would be able to tell the gap and angle between themselves a few times a second, giving me a kind of scatter graph of positions over a given time.

 

[MattH]

Me neither, which is why i'm having a problem. In my mind, I had imagined strapping a clever box of electronic trickery to a fixed point and then another box of trickery to one of the moving objects, and then these clever boxes would be able to tell the gap and angle between themselves a few times a second, giving me a kind of scatter graph of positions over a given time.

Which would generally required laser, ultrasonic or low level radar, all of which would require line of sight.

 

[Climber]

Which would generally required laser, ultrasonic or low level radar, all of which would require line of sight.

Yep, that seems to be my problem.

Does anyone have any recommendations of kit that may work if i could make sure they always had line of sight?

 

[rikrobson]

You can use Bluetooth if the range is less than 10m
Eash node will be a Bt device with an I'd and you will need some fixed points to triangulate off. You v an then use the built-in power detection to triangulate each node

 

[Climber]

You can use Bluetooth if the range is less than 10m
Eash node will be a Bt device with an I'd and you will need some fixed points to triangulate off. You v an then use the built-in power detection to triangulate each node

Now that is interesting. Thank you. I'll do some Googling.