How to measure distance between two objects wirelessly?

[pawan7]

So I want to measure the distance between two objects wirelessly, which should preferably give out the same type of waves to do so.

 

My prediction is that slower the speed of the wave, more accurate we can measure the distance between the transmitting objects.

So radio waves or sound waves are much slower than Bluetooth which works at the speed of light? if I'm correct.

 

I'm a complete novice to every form of science, especially physics. So please tell me the most accurate and the most energy efficient way of calculating the distance between two variable objects wirelessly. It does not have to consist of a method of waves.

 

Thank you,

 

Waiting in anticipation

 

 

[mathematic]

Radio waves are electromagnetic - same speed as light.

 

Sound waves might be used. Speed is affected by atmospheric conditions, particularly temperature.

[pawan7]

So what would be the precision of sound waves used? would it be inches? and would it still work if it is possibly covered by something?

[studiot]

I am not sure what method you want to use.

 

If you are measuring the time interval between sending and receiving a signal than yes the longer the time interval the more accurately you can measure it (within reason)

 

So a slower signal would give more accurate distance reading if you knew both signal speeds to the same accuracy.

 

If, however you want to use the wave properties to measure distance then speed is immaterial. What counts is the wavelength. the shorter the wavelength the finer the resolution of your measurement.

[pawan7]

Ohh okay, So I do want to measure the distance between two objects. The preferable accuracy is a foot or an inch. So the best wave would be sound wave for this accuracy?

[Cap'n Refsmmat]

There are plenty of little devices made for measuring distance with sound. Here's one:

 

https://www.sparkfun.com/products/639

[Sensei]

So please tell me the most accurate and the most energy efficient way of calculating the distance between two variable objects wirelessly. It does not have to consist of a method of waves.

 

For Earth's scale objects typical method is sending photons to object and after reflection, detecting returning signal delay (t=2*d/c)

It's used in radars, using radio waves.

But if you attach mirror to object, or retroreflector (like on Moon), you can use normal visible range photons.

For our solar system and galaxy scale distant objects we can use knowledge about position of Earth around Sun and Pythagoras triangle.

At one day of year Earth is closer to some star or planet, at other day of year Earth is farthest from it.

 

You can deduct that tangent alpha is equal to ~1 au (=~150 mln km) divided by distance to measured object (from Sun).

 

I have made picture for you to visualize:

 

Edited May 10, 2014 by Sensei

[swansont]

You can use a laser to do it, too. There are commercial products, usually called laser distance finders or possibly electronic tape measures (though those might also include acoustic devices.

[Mordred]

ultrasonic/infrared distance sensors are good for this, Banner engineering has a good product line

http://www.bannerengineering.com/en-US/search?k=distance+sensors&search_type=all&x=0&y=0

 

there manuals also include the related distance/time measurements including the electronic reaction times

[pawan7]

Ohh I see. Thanks for all the replies. but my objective is to measure distance using the integration wave of a smart phone such as bluetooth, radio waves and so to calculate the distance between another object which may be hidden under something or behind something, so therefore the light ray idea will not work. Any solution?

 

I think radio waves, infrared, sound, Bluetooth or even Wifi(if there is a ray that exist) is the most suitable?

[Mordred]

whether you use radio waves, microwaves or other forms of electro magnetic waves will work, radio waves is after all how radar works, sonar is sound waves, infra red or ultrasonic sensors use light waves. Your calculations is the speed of light or sound traveling through a medium. This is particularly important in sound waves. Its time based, between time of emission, time of receive with the corresponding rate of travel through the medium.

[studiot]

 

whether you use radio waves, microwaves or other forms of electro magnetic waves will work, radio waves is after all how radar works, sonar is sound waves, infra red or ultrasonic sensors use light waves. Your calculations is the speed of light or sound traveling through a medium. This is particularly important in sound waves. Its time based, between time of emission, time of receive with the corresponding rate of travel through the medium.

 

 

There is at least one other way, that I referred to in post#4 than time of flight measurements. These do indeed work around corners and obstacles, but introduce different issues.

I was waiting for a better description of the problem from the OP.

[Mordred]

 

There is at least one other way, that I referred to in post#4 than time of flight measurements. These do indeed work around corners and obstacles, but introduce different issues.

I was waiting for a better description of the problem from the OP.

I take it your using the doppler shift in this method?

[studiot]

 

I take it your using the doppler shift in this method?

 

 

No not at all.

 

Phase methods were popular before precise timing became possible.

 

Think names like Loran, Decca, Tellurometer

 

Interference methods were also used, think Geodimeter. and the NPL one whose name I can't remember.

 

But we need proper specification from the OP.

Edited May 11, 2014 by studiot

[Mordred]

gotcha, just wasn't sure which frequency method you were referring to.

[Bignose]

You can use a laser to do it, too. There are commercial products, usually called laser distance finders or possibly electronic tape measures (though those might also include acoustic devices.

This was my first thought too. I do this all the time with my laser rangefinder on the golf course. It reports to a tenth of a yard, though that is absolutely overkill for the level of my game...