http://www.ifixit.com/Teardown/iPhone-4-Gyroscope-Teardown/3156/1
Who will write software to track the movement underground?
m.
Who will write software to track the movement underground?
m.
Next generation?
- Thread starter sluka
- Start date
You can of course buy mems gyros and make your own a lot cheaper than an iPhone and probably a lot more robust.
In terms of tracking movement underground I've been thinking about it for a few years. The difficulty comes down to distance measurement, an IMU (inertial measurement unit) made up of 3 axis accelerometers and 3 axis gyros (and you could chuck in a 3 axis magnetic sensor as well) will give you orientation but distance travelled is a lot harder to determine.
In terms of tracking movement underground I've been thinking about it for a few years. The difficulty comes down to distance measurement, an IMU (inertial measurement unit) made up of 3 axis accelerometers and 3 axis gyros (and you could chuck in a 3 axis magnetic sensor as well) will give you orientation but distance travelled is a lot harder to determine.
Cave_Troll
Active member
surely you measure the acceleration for a certain time and work out the speed. then work out the distance.
Peter Burgess
New member
You could tag novices with one of these to make sure they stay out of Charterhouse caves..... :tease:
AND the second integral converts the slightest noise into large errors - it's one of those things that is hard to believe but you can try it in a spreadsheet. Create a column of small random numbers (in Excel you can use =RANDBETWEEN(-100,100)/1000) then compute the first and second integrals - it's a lot easier than it sounds, basically just add the next number to the sum of the previous - for initial numbers that average zero can end up with a significant error.
mountainpenguin
Member
dont forget you can cheat quite a bit.
For example there is an electronic compass so its now a gyrosocope plus direction.
Add in barametric altimeter and you have another data source.
Then a clever interface that lets you mark a been here before points and you can reduce the errors a bit more.
Not perfect but starting to get a lot easier.
For example there is an electronic compass so its now a gyrosocope plus direction.
Add in barametric altimeter and you have another data source.
Then a clever interface that lets you mark a been here before points and you can reduce the errors a bit more.
Not perfect but starting to get a lot easier.
I suppose it depends on what you want the data for, 20% error may be achievable but then is it any use? I did some experiments on using video to measure distance and on a flat surface (my patio) I could get to around 1% but on uneven surfaces the accuracy dropped away quite a lot.
FWIW - the technique I tried was fastening a laser pointer to the camera parallel to the axis of the lens. The distance from the centre of the lens to the laser dot on a surface is then always the same, so the number of pixels between the dot and the image center is known, so from this if you know the number of pixels moved between two frames you can get the distance moved between frames. I used the OpenCV library to do the image processing and optical flow.
The issue with uneven surfaces is that the distance to each feature in the frame varies so the features being tracked may not be at the same distance from the camera as the surface on which the laser dot falls.
FWIW - the technique I tried was fastening a laser pointer to the camera parallel to the axis of the lens. The distance from the centre of the lens to the laser dot on a surface is then always the same, so the number of pixels between the dot and the image center is known, so from this if you know the number of pixels moved between two frames you can get the distance moved between frames. I used the OpenCV library to do the image processing and optical flow.
The issue with uneven surfaces is that the distance to each feature in the frame varies so the features being tracked may not be at the same distance from the camera as the surface on which the laser dot falls.
