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Distance Measurements to Target

Hi, we are currently using the Microsoft Lifecam-3000 with a raspberry pi for vision tracking and distance measurements. We can find the pixel height of the bounding box of the two vision rectangles and are inputting it into the equation:

distance: 0.83 (actual height of bounding box (ft)) * 480 (y-pixel resolution) / 2 * pixelHeight * tan( 14.9 (vertical view angle in degrees) )

When testing this formula, we have found that distance measurements are within 2-3 in. when the target is 2-4 m. away; however, from 1- 2 m, the error is around 10 in. We were wondering if there is anyway to prevent this, or if there is another, more-robust method to calculate the distance to the target.
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Re: Distance Measurements to Target

https://acroname.com/products/r93-srf04?sku=R93-SRF04

This is an ultrasonic distance sensor. It is great for this application
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Re: Distance Measurements to Target

The easy method using the camera is an empirical curve.

That is, position the robot at a series of measured distances from the vision target, take pictures and measure the vertical height. Then, use you measured height during the match and interpolate into the curve you measured.

It will likely require re-measurement if you move the camera to a different location.
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