figuring out correct lenght and width with pixels

asked 2018-01-11 17:01:59 -0500

hi, I'm trying to figure out length and width of an object on a picture with pixels. Camera that takes the picture is always in the same position, only objects will change.... as example I take a picture from a US quarter from a distance of 10 inches.. to calibrate I calculate how many pixels the US quarter has (in my instance lets call it 150 pixels per 0.955 inches).. if I stack 25 quarters on top of each other will I still be able to get a somewhat accurate measurement or is this not possible?

Also would it work any better if I have an image from the top and one from the front?

Thanks for helping at this project!

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Comments

If you stack on the top of each other you will not get accurate answer. Top image will give you better results. If you have oblique image ortho-rectify it. If you are facing any problem with Ortho-Rectification then let me know.

ak1 gravatar imageak1 ( 2018-01-16 04:59:18 -0500 )edit

Thanks aniket1. is there a way to calculate the change of height based on pixels? i checked and based on the original distance from the camera to 1 coin i have 127 pixels per inch... if i stack 25 coins on top of each other will i have more pixels and therefore can calculate how high the quarters are stacked?

As example i start with 1, then 2 and measure pixels, then 3 and measure and so on?

do you think this would work and i could use the same technique then to measure other objects and length and width and get accurate measurements?

ortho rectification will not be used as my camera is at a perfect angle.

Thanks!!!

newb1986 gravatar imagenewb1986 ( 2018-01-16 20:02:47 -0500 )edit