Resources for Understanding Photogrammetry in 3D Scanning

[[Mi...]]

I am looking to understand the science/technical-workings behind photogrammetry a little better. In particular, as it relates to use in a Scan Box and the Zeiss/GOM Inspect software.

I came across this video earlier today and learned somethings I did not know, but it only scratches at the surface of the concept of photogrammetry and seems to be more orientated towards the application of photogrammetry in a field like photography: https://www.youtube.com/watch?v=rh6xZ5sb31M 

I have a few questions:

• Does any one have any useful links / videos / resources on photogrammetry for learning purposes?
• Is it correct to say that coded reference markers are required to run photogrammetry in the Zeiss Inspect software? Otherwise, the uncoded reference markers cannot be located (in photogrammetry), and you would instead need to run a regular ATOS measurement series with uncoded reference markers placed on your part?
• How much 'accuracy' is lost by not using coded refence markers and only using uncoded reference markers?

[[Ja...]]

Hi mike to answer part of this , yes coded markers are required for photogrammetry to function in gom/zeiss solutions.

It is hard to articulate the accuracy beneift it brings but it provides a more stable generalised base accuracy to around 10/15 microns per meter .

If just using atos it is a general rule/advisable to always use photog when the part is over twice the measurement volume of the atos system.

[[Mi...]]

Please sign in to view this username.

Thank you for the response, James. I came across another post from about a year ago and to my understanding Photogrammetry is more stable because you don't need overlapping images (which can accumulate small bits of error with every image).

[[Ja...]]

The way i used to explain it was to imagine a long table and start scanning at one end , overlapping as you say increments the error to a point where in the end the data from the table will be bent /warped .  Hence why the general rule of thumb on using it as the use of phog g eliminates this stacking issue .I

The other minor benefit of this is needing less markers overall.

My other advice was if you have access to use photog just use it ! It doesnt take long for the benefits it brings.

May i ask what your application is or are you just curious how it works?

[[Mi...]]

Please sign in to view this username.

Sorry for my slow response. I got busy with some work tasks and life stuff. I've heard your analogy in a class that I took previously and it makes sense. It's kind like tolerance stacking.

Can you speak at all to the longevity of reference markers (i.e.: how long they last)? I see another minor benefit in that with photogrammetry, you're not stickering every part that comes through the door. You just need to sticker your fixturing once.

Aside from needing to replace damaged reference markers as they are found, is there a "prescribed" timeline for how long you can go before needing to re-sticker an entire fixture? I figure you'll know if when looking at your photogrammetry results, you notice that you have much less coded and uncoded reference markers than expected.

I work in aerospace and usually on airfoils, but I am only asking questions on Photogrammetry to improve my knowledge. I like being to confidently understand a topic and to be able to explain it well to others.

 

[[Aa...]]

We perform Photogrammetry on our cage's once a year. We are also in Aerospace.