I am trying to find a way for two arduinos to both find and communicate the distance between each other through any known material (namely underwater). Going the way of ultrasonic and infrared, I know this is nearly impossible to do with accuracy; however, I know that this has been done to within 15 meters by radio wave. The radio wave experiment was rudimentary and was relatively inaccurate due to the processing speed, seeing as how radio waves travel at about 30cm/nanosecond. In short: what is the best way to go about this? Is there an arduino processor fast enough to handle registering discrepancies so small? Small enough to get a reading within...say...6cm? Or maybe even 30cm?
As a follow-up, would I be better off finding the distance between 4 sensors and a gyro to create a grid in 3space or finding location based on distance and direction?
Is there an arduino processor fast enough to handle registering discrepancies so small?
No.
would I be better off finding the distance between 4 sensors and a gyro to create a grid in 3space or finding location based on distance and direction?
Underwater is hard. Really hard. Don't tell me you also have solid objects between the two Arduinos so you can't use a physical measuring tape or string?
jremington:
This question makes no sense. Try rephrasing it.
the follow up question is just if i can find the first part of my question.
MorganS:
Underwater is hard. Really hard. Don't tell me you also have solid objects between the two Arduinos so you can't use a physical measuring tape or string?
I could tie a string, of course, but, of course, I'd rather not.
My mention of the fact that your question comes up all the time was a hint that you should do some research.
Since people ask this question on this forum one or more times a week, this forum is one place to start your research. There are many threads where people go to some length to explore and discuss the possibilities.
For more general overviews, google "indoor localization", keeping in mind that underwater localization is much harder.
Other than GPS outdoors, no one has reported success with any proposal for how two Arduinos can determine their locations, or the distance between them. However, overhead video cameras connected to PCs have been used to localize robots for many years.
jremington:
My mention of the fact that your question comes up all the time was a hint that you should do some research.
Since people ask this question on this forum one or more times a week, this forum is one place to start your research. There are many threads where people go to some length to explore and discuss the possibilities.
For more general overviews, google "indoor localization", keeping in mind that underwater localization is much harder.
I've searched a ton of forums, but I hadn't tried looking up indoor localization. Thank you.
I don't see why you can't try with (200khz) ultrasound. Distance only though.
1.5m distance is only ~1msec.
You need two encapsulated omni directional piezo elements, and the last time I tried to find one they were US200 each.
Leo..
jremington:
How do you suggest that the OP use sound to measure the distance between two Arduinos?
One way would be to have the "sending" Arduino communicate with the other Arduino via some communication medium that is faster than sound - RF or light (IR) would work OK.
Basically, the concept would be that Arduino (1) would send a message (say via radio) to Arduino (2) to tell it to start a timer counting and wait for the ping. Arduino (1) would then ping its ultrasonic transmitter, and when Arduino (2) heard the ping, it would stop its counter. The count would be proportional to the distance between the two Arduinos, and Arduino (2) could relay that value back to Arduino (1), if needed.
Note that you likely couldn't use standard ultrasonic distance measurement sensors (ie - SRF-04 or SRF-05, etc); not without some modification, at least.
A depth sounder or fish finder sends a 200Khz burst, and then switches to receive (same element is used).
I suppose you can do the same with two Arduinos.
And calculate the distance from the time it takes to hear back from the other one.
Very difficult project I think. Not suitable for a beginner.
I once have build directional underwater microphones to locate whales.
Full of pitfalls....
Leo..