Jump to content
bjenk8100

back to picture to cad

Recommended Posts

This might work. Get two string lines from porch or whatever part of house/structure and plum line it out level to area straight away from structure. We have string lines with levels. Then level a stand perpendicular to string lines with camera. That way it is straight shot unless I am missing something. Then picture should be traceable. Then measure 1 object physically and scale it in cad. If I am missing something please feed.

Share this post


Link to post
Share on other sites

Why? there are programs that do this. If you are going to go to all the trouble of usings strings and levels. for every picture you may just as well measure the stuff.

Share this post


Link to post
Share on other sites

we run outta manpower. surveyors r doing government jobs. if this works i will be fond. I cant take the heat to bring union onto residential with all that crap. I want to do it myself.

I love the unions they do good for me but they are not good at particular crafts. I teach them carpentry and they laugh. "Thats too artsy"

Edited by bjenk8100
forgot something

Share this post


Link to post
Share on other sites
This might work. Get two string lines from porch or whatever part of house/structure and plum line it out level to area straight away from structure. We have string lines with levels. Then level a stand perpendicular to string lines with camera. That way it is straight shot unless I am missing something. Then picture should be traceable. Then measure 1 object physically and scale it in cad. If I am missing something please feed.

 

That will work. If you get a camera perfectly perpendicular to the plane of the measurable object, other objects on that plane can be measured. Those other objects, though, have to be coplanar. Not just parallel, but perfectly coplanar.

 

Experiment with AutoCAD, a camera, 3d Solids, and the Flatshot command to confirm or refute any of these notions.

Share this post


Link to post
Share on other sites

Perfectly coplanar! Imagine a window opening 1 meter wide, with a window frame set back in the opening by just 10cm it is still in reality 1 meter wide. Now take a photo with the camera at a distance of 2 meters perfectly in front of the brickwork. And scale your photo so that it shows the brickwork opening at 1 meter then your window frame will measure just 952.381 mm. If your happy with that level of inaccuracy then OK but be aware measuring from a flat photo will only work if you are taking photo's of perfectly flat objects, and then you need to take into account photographic perspective.

Share this post


Link to post
Share on other sites
Perfectly coplanar! Imagine a window opening 1 meter wide, with a window frame set back in the opening by just 10cm it is still in reality 1 meter wide. Now take a photo with the camera at a distance of 2 meters perfectly in front of the brickwork. And scale your photo so that it shows the brickwork opening at 1 meter then your window frame will measure just 952.381 mm. If your happy with that level of inaccuracy then OK but be aware measuring from a flat photo will only work if you are taking photo's of perfectly flat objects, and then you need to take into account photographic perspective.

 

That all sound about right.

Share this post


Link to post
Share on other sites

All pictures are a perspective view. Although you can get a good approximation if you are far enough away, you cannot get truly accurate dimensions.

Share this post


Link to post
Share on other sites

A guide to architectural photography states, "By photographing your architecture from a long way away and using a long focal length lens (telephoto), you will flatten the perspective, making the lines of the building appear parallel..."

 

You might also want to read up on tilt shift lens useful in "eliminating the convergence of parallel lines". This is especially true when photographing tall buildings.

Share this post


Link to post
Share on other sites

You are talking about Photogrammetry, making measurements from photographs. You could always take lots of pictures and as many measurements as possible and then use SketchUp's Match Photo tool to create a 3D model of the structure/facade and then bring that back into AutoCAD. Your profile says you are using AutoCAD 2018 and AutoDesk has a free import SU file add-on.

https://help.sketchup.com/en/article/3000115

Scroll down to 'Creating a 3D model from a photo'

Other examples on YouTube

 

As Rob says you will not get accurate dimensions but you can get a good start.

Share this post


Link to post
Share on other sites
All pictures are a perspective view. Although you can get a good approximation if you are far enough away, you cannot get truly accurate dimensions.

True at 100 meters away it would make the difference of the window opening and the frame just 1mm, but it might be a bit hard to pick details from a photo at that distance. :shock:

Share this post


Link to post
Share on other sites

The notion of dealing with parallel, though not coplanar, geometry got me thinking . . . . So, I'm posting a setup for testing Image to Cad Data techniques.

 

The file doesn't actually contain an image - just a basic model and some FLATSHOT geometry - but I think we can treat that as traced geometry from a photograph of some comparable test structure.

 

I going to make a screencast using the app (Projective2D) I mentioned in the similar thread from a week ago. I will post that link when it becomes available.

PerspectiveTest.dwg

Share this post


Link to post
Share on other sites

Thanks guys. Non parallel measurements are proving to be quite a bit more tricky, but I may be onto something that could be included with my add-in. Still needs some refinement - I'll see how it works out.

Share this post


Link to post
Share on other sites

Yeah, I learned a lot from watching that demonstration that I'm sure I'll use in the future.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×