Thread: Obtain measurements/scale from photo

Well, here's how I would do it...

Print photo nice and large, find 'something' in the photo of a known or estimatable size (say like a wheel or a street sign or a kerb or a brick or....), You've now got your point of reference for size - measure it and work out the scale.

If the photo is not square on, you then have to do some trigonometry to account for perspective...being disinclined to dust off maths skills, I'd load the photo into photoshop and play around with un-perspective-distorting the image and print that image for measurement purposes!
Perspective control - Wikipedia, the free encyclopedia

find something in the photo to relate to. It might be in the background but it gives you a size to go on.
Phil

Yes, it can; at least for planar objects - no good for 3D.

Most likely, the photo isn't straight-on; instead, it's a perspective image, with "keystoning," in which rectangles are distorted into trapezoids. Essentially, you need to transform the trapezoid(s) back to its/their true shape(s). After that transformation, you'll need a reference length to establish a scale factor for the whole - that's the easy part.

Consult your Yellow Pages or Google for "Drafting Services" or "Graphic Designers." Seek a practitioner with strong capabilities in Descriptive Geometry.

An alternative, less precise way, would be to GUESS at the size/shape, and GUESS at the angle of photography. Draw a suitable grid and photograph it at the same angle. Print the picture on transparent media, and overlay the original photo to measure directly at the warped scale.

Cheers,
Joe

Can't help on this one, Scott,
But I'm sure Fozzy can as he's great with building what he sees....
If he doesn't post a note on the thread, send him a "PM".
Cheers, crowie

Yes its possible BUT as discovered many years ago when doing this even with a 2D type photo of the side of a vehicle. When prints/film was produced there can be an error of up to 10%. When developing was taking place to focus correctly images and lens on the developer were adjusted, cropped and resized.

Ok so you say pffttt today is all digital, well sorry but from camera to chip to computer to printer adjustments are made for you.

But hey these are for toys and true to scale is not paramount as they say "Close enough is good enough"

Thanks for your valued responses gents, I'll PM Fozzy Crowie, thanks.

I found exactly what I wanted at this link:

blueprints.com

I'll work off the blueprint plus the photo I have.

Thanks once again.

Originally Posted by wheelinround

But hey these are for toys and true to scale is not paramount as they say "Close enough is good enough"

I agree with Ray, what's a few inches matter in a big country like Australia. just as long as you get both sides the same length you don't have a problem. One side longer than the other? you have a problem.

So what are you building Scott? Curious minds want to know.

Bret

Originally Posted by bj383ss

So what are you building Scott? Curious minds want to know.

My neighbour across the road collects vintage tractors, all of them operational. I've actually had a go at driving a few of them around the paddock. He has a photo from the net of a particular tractor he want's to model. I made the fatal mistake of showing him some models I've made plus some of the Gatto plans. He's a car mechanical engineer by trade so he's going to collaborate with me to get the plans drawn close to scale as possible (image from net attached).

Something tells me I've bitten off more than I can chew.

Originally Posted by sjt

My neighbour across the road collects vintage tractors, all of them operational. I've actually had a go at driving a few of them around the paddock. He has a photo from the net of a particular tractor he want's to model. I made the fatal mistake of showing him some models I've made plus some of the Gatto plans. He's a car mechanical engineer by trade so he's going to collaborate with me to get the plans drawn close to scale as possible (image from net attached).

Wow Scott, That sure is a big project.
When I did my RAN Apprenticeship at HMAS Nirimba in the very early 1970's our mob started the restoration of a Foden Traction Engine.
I think it's still an RAN icon and housed down at HMAS Cerberus,Frankston.
Great piece of machinery.
Cheers, crowie

Would this help you? Not exactly detailed but might give you rough dimensions.
Attachment 192579

Bret

Found this:Attachment 192580

On this website: Steam Engine Plans

Bret

Bret! You've excelled! Thanks, I shall now bow to your awesomeness. I've just showed them to my neighbour who is ecstatic. Thank you.