**Development issue/problem:**

Can I measure the distance to an object with my phone’s camera?

In my application, I start the camera in front of an object (like a house), then I press a button and it calculates the distance and shows it to me on the screen.

If possible, where can I find instructions or information on how to proceed?

**How can I solve this problem?**

**Solution 1:**

Well, you should read up on how ithinkdiff.com measures distance:

Uses the iPhone’s angle to estimate the distance to a point on the ground.

Hold the iPhone in front of you, align the dot in the camera and get a direct measurement of the distance

. The distance can be used in a speed tool.

Basically, this means taking the height at which you are holding the phone (at eye level) and then pointing the camera at the point where the object touches the ground. The phone then measures the slope and calculates the distance using simple trigonometry.

Of course, it’s not very precise. The further away from the object, the less accurate it is. It is also assumed that the ground is flat.

**Solution 2:**

I recognize that the question has been adequately answered (with obvious reservations about the need for a flat floor and possible accuracy issues), but for those who don’t believe it can be done or that it requires a video camera, let me explain that it requires low-level math….. requires.

In the picture above I am standing in front of the house. The horizontal (d) is the distance I want to measure and the vertical (h) is the height above the ground where I am holding the camera. In this case, h is a known value when I hold the Android camera at eye level (about 1.7 meters). If I tilt the camera to point it directly at the point where my house touches the ground, the software only needs to calculate the angle (a) from the vertical and can calculate d with …

d = h * tan a

**Solution 3:**

No. A camera can only give you image data, and the image alone does not give you enough information to inform you in depth. If you have multiple images for which you have location information, or even a video, you can process them to triangulate the distance, but a single image will not be enough to determine the distance.

**Solution 4:**

You can use the technique that our eye uses to get the perspective of depth and distance.

1) Take 2 photos of the same object from two different camera positions.

2) The distance or pixels between the objects in the 2 images are inversely proportional to the distance between the camera and the object.

Implementation is available at https://github.com/agnelvishal/Distance-between-camera-and-object

. The research paper is available at http://dsc.ijs.si/files/papers/S101%20Mrovlje.pdf.

**Solution no. 5:**

You have an angle in your phone’s accelerometer. If you calculate the tangent to this angle and multiply it by the height of the camera lens, you get the distance.

**Solution no. 6:**

I believe this application uses the approach mentioned by MisterSquonk (it’s free). Note the trigonometry technique.

**Solution no. 7:**

I think you can use FastCV to calculate the distance between the camera and the object. You don’t need to know the angle or position of the camera you are holding above the ground. see this question here

**Solution no. 8:**

One way to do this is to use DPI in your device. You can take a picture and calculate the height. But you need another object as a reference, and then you can know that the problem with this method can be a perspective between the objects.

**Solution no. 9:**

I think you can do it with a cell phone camera. I know modern phones use lenses to focus on a subject. If you can determine their focal length and position (offset) to focus on the selected object, you can also determine the distance.

**Solution no. 10:**

No. Only with two cameras in stereo mode, like the xbox 360 kinect. At least 3 points are required for distance triangulation.

**Good luck!**

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