How to measure height, width and distance of object using camera?

Question

I referred lot many links but still I am not able to get any point from that I can start my development. I want to measure my image height, width and distance using camera. I found this app . I want to make this type of application not exactly same but quite same but for my requirement I want to measure my image height, width and distance using camera.

Can anyone give me/suggest me the right way or any example so that I can get more idea about this requirement.

I tried this :

http://android-er.blogspot.in/2012/04/gets-distances-from-camera-to-focus.html

If you have found any solution can u please mail me the source code to find distance,width and height of any object.Please?? — Chiradeep, Aug 29 '13 at 13:15
I am facing the same problem. Please help me.If any idea.Thanks in advance.. — Jagdish, Jun 20 '14 at 07:29

score 36 · Answer 1 · answered Jan 28 '12 at 11:14

36

I think I know what you are asking for. Here is what you can do.

first get the height of the person say h meters.

sample image

if you can calculate the height of the camera from ground (using height if the person i.e. h) and get angles A and B using gyroscope or something from android then you can calculate the height of the object using the above formula.

Isn't this what you were looking for???

let me know if you need any explanation.

answered Jan 28 '12 at 11:14

drulabs

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did it worked on android? I have tried but not working? if you have sample demo can you upload it some where it can help others.. :) – Sumant Nov 30 '12 at 12:44
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it's really difficult to calculate "h" value - there is no API for this! – Stan May 29 '13 at 15:39
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no api needed. Use math to calculate H using the formula. "h" is what you have to assume based on person's height. Maybe take the height of the person as input. – drulabs May 30 '13 at 04:51
this actually worked in iOS. I got the user's distance from the object and used this to compute the top half of the height of the object. – Keale Oct 17 '13 at 07:47
@Keale, can you provide me some sample code please? – Akshit Zaveri Mar 17 '15 at 14:55
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What about when the object is inclined at an unknown angle itself? – Akshit Zaveri Apr 03 '15 at 17:15
Can you please explain what A and B means? And where exactly do we use the distance? – Sorin Haidau Sep 22 '18 at 09:54
A and B are the angles of elevation & depression respectively. – drulabs Sep 23 '18 at 10:20

SpeedBirdNine · Answer 2 · 2012-01-28T11:58:29.440

For measuring distances with a single camera, you need to know some numbers. To measure height of something, say a chair, the only thing you have is the the size of it in the camera (which is in pixels, and can be converted to inches using screen size), that is all. The chance of measuring the height and width is using a reference, say a 6 foot tall person standing next to the chair.

This way you can work out in reverse using say a 10 foot tall object, using its size as appearing in the camera, you can work out the size of things at the same distance, on a surface that is not flat, even ensuring that they are at the same distance is a challenge.

So using the camera and just the camera, it is not possible. You need to know distance somehow, or need a reference.

If you are using the application to measure height of items you know the location of, then using GPS, you can find distance, and rest is math.

I have found some links using Google, they may help.

They may help you to find out what other information is needed other than what the camera can provide, so that you can think about your application as well regarding what can be done and what are the limitations.

One way is using multiple cameras, and that can be compensated using multiple pictures taken a known distance away. So the application can ask the user to take multiple images, track the distance using GPS, and probably it can work.

See these links as well:

score 9 · Answer 3 · answered Jan 02 '12 at 08:47

9

If you know the viewport angle of the camera, you can use the height in pixels to determine the angle from the top to bottom of the object. Then, using the distance and arctangent calculate the height:

height = arctan(angle) * distance

To find the viewport angle, point the camera at something which is of known height, and make it exactly fill the screen. For example, point it at a ruler, and make it just far enough away that you can only barely see the ends of the ruler. Measure the distance from the camera, and then your total viewport angle is

viewportAngle = tan(ruler_length / distance)

Then, suppose your camera is 480px tall (cheap webcam), and the view angle is 20°. If you have an object onscreen which is 240px tall, then its angle is 10°. If you know it's 2 feet away, you would say 2 feet * arctan(10°) = ~4.1 inches tall. (I think... it's 2am so this may be a little off)

answered Jan 02 '12 at 08:47

Tim

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good but as pointed by @Péter Varga you need to know distance from object. – TheVillageIdiot Jan 02 '12 at 08:49
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It seems that app uses the accelerometer to measure the angle to the base of the object, and then assumes a height of the phone off the ground (typically around 5 ft) to measure the distance. You could do something like that but it wouldn't be particularly accurate. – Tim Jan 02 '12 at 08:54
@Mansi You should first get an idea for the conceptual methods used before writing any code. http://en.wikipedia.org/wiki/Inverse_trigonometric_functions – Tim Jan 02 '12 at 08:55
Can you give me any example link related to this? So I can get more idea still I am not exact understanding your point. – anddev Jan 02 '12 at 08:58

score 4 · Answer 4 · answered Jan 30 '12 at 09:02

If you think about it, a body XRay scan (at the medical center) too needs this kind of measurement for estimating size of tumors. So they place a 1 Dollar Coin on the body, to do a comparative measurement.

Even newspaper is printed with some marks on the corners.

You need a reference to measure. May be you can get your person to wear a cap which has a few bright green circles. Once you recognize the size of the circle you can comparatively measure the remaining.

Or you can create a transparent 1 inch circle which will superimpose on the face, move the camera toward/away the face, aim your superimposed circle on that bright green circle on the cap. Then on your photo will be as per scale.

P Varga · Answer 5 · 2012-01-03T09:39:04.793

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You can't.. You would have to know:

How far is the object (you can know your location from GPS.. but the object's location?)
What is the focal length of the camera

Maybe, just maybe if the object was optically tagged with for example a QR code, and you have a code-to-loc map...

edited Jan 03 '12 at 09:39

answered Jan 02 '12 at 08:47

P Varga

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If you knew the view angle of the camera... – P Varga Feb 25 '12 at 15:53
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yes that is possible. here: http://stackoverflow.com/questions/5284493/get-angle-of-elevation – drulabs Feb 27 '12 at 07:29

score 1 · Answer 6 · answered Jan 27 '12 at 12:19

First of all i will say Nice Thaught to develop such app.

Now i am not sure about it, but if you can able to get the face-detection like thing for any object in android camera so with help of that you can achieve that things.

Well i am not sure about it but still have give some view so you can get idea of it.

All the Best. :))

How to measure height, width and distance of object using camera?

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