Forum

Author Topic: Creating an Accurate 3D Model that is Easy to Measure  (Read 252 times)

captcook42

  • Newbie
  • *
  • Posts: 2
    • View Profile
Creating an Accurate 3D Model that is Easy to Measure
« on: May 18, 2020, 06:10:16 PM »
Hello!

I have been working on learning to use Agisoft over the past 6 months or so and I've found that it is relatively intuitive. I have, however, run into a bit of a wall when it comes to a current project.

I have a lot of drone imagery of a standard highway bridge. The imagery is taken by the drone from above the bridge (to capture the bridge deck surface), the sides of the bridge (to capture the fascia), and beneath the bridge (to capture the substructure and the road beneath the bridge).  This is a 100 meter long (or so) bridge, and because of the number of angles the imagery is captured from this is a large file (~800 or more photos). A medium quality dense cloud comes to 73 million points, and a medium quality 3D model comes to 1.7 million faces.

My issue is that it can be frustrating to use the measurement tool on this particular 3D model. Maneuvering the view such that I can see a specific part of the substructure of the bridge can be difficult or impossible because another part of the bridge might be blocking the view from most angles. For example, if I want to measure the width of a crossbeam under the bridge, I can maneuver the view perspective such that I'm sitting on the road under the bridge and looking upwards at the underside of the bridge, but if I try to zoom out at this point then the ground underneath the bridge will obstruct the view. It can be impossible to get the feature I want to measure to fit entirely within the view window.

What I would like to be able to do is have the bridge divided into separate chunks (e.g. chunk 1= bridge deck, chunk 2= bridge deck substructure) so that I can turn a chunk "off" so that chunk 1 does not obscure my view while I measure chunk 2. I would also like to be able to view both chunks at the same time (one on top of the other). I would also like to have these same chunks combined into a single model (preferably with similar positional accuracy) that I could use for visualization or to be shared with collaborators in Agisoft Viewer. Is there any workflow that might help me do the above?

Alternatively, is there any way to click a start measurement point, move the view, and then click the ending measurement point? It seems like I am unable to move the view while in the process of measuring a feature.

Thank you so much!
-captcook42

EDIT: When I refer to "making a measurement", I'm referring to using the "Ruler" tool. Thanks!
« Last Edit: May 18, 2020, 06:14:14 PM by captcook42 »

James

  • Hero Member
  • *****
  • Posts: 659
    • View Profile
Re: Creating an Accurate 3D Model that is Easy to Measure
« Reply #1 on: May 19, 2020, 11:22:46 AM »
Sounds like the Tools -> Mesh -> Filter by selection tool might help here.

You make a selection, then apply the filter, and can then reorient the view to make a further selection and filter and repeat as necessary. Then make your measurements unimpeded and reset the filter when you want to see the full model again.

captcook42

  • Newbie
  • *
  • Posts: 2
    • View Profile
Re: Creating an Accurate 3D Model that is Easy to Measure
« Reply #2 on: May 21, 2020, 10:34:24 PM »
Thank you for your response! I will try out what you recommended and post any questions I have here.

-captcook42

JMR

  • Sr. Member
  • ****
  • Posts: 368
    • View Profile
Re: Creating an Accurate 3D Model that is Easy to Measure
« Reply #3 on: May 23, 2020, 06:45:05 PM »
In my opinion the built in measurement tools is almost unusable but for very rough and fast queries, the measurement resolution changes inconsistently from one measurement to another, measurements are not persistent, you cannot take several measurements at once without doing accumulative, etc... I never use this tool. However, with regard to your question, yes, filtering by selection will somehow replace one long term missing feature yet standard in plenty of programs: clipping boxes.
Also, your complain about not being able to move to another place during measurement is not right. You actually can pan, rotate and zoom to another place from one measurement end to the other:
ctrl+shift+left button down+drag for view rotation (also works with al+shift+left button down+drag)
shift+left button down+drag up and down for zoom in/out (the mouse wheel is also working)
ctrl+left button down+drag for panning (also works with alt)

My suggestion for accurate measurements it is to use scale bars and get distances from estimated values of distance. An alternative is drawing lines and later retrieve their length by means of the shape measurement tool.

Regards
GEOBIT