# figuring out correct lenght and width with pixels

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!

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.

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!!!