Forum

Author Topic: Calculation of 3D-Area  (Read 2067 times)

SebastianStumpf

  • Newbie
  • *
  • Posts: 8
    • View Profile
Calculation of 3D-Area
« on: October 04, 2021, 09:25:10 PM »
When drawing a polygon, the 2D-Area can be measured, but not the 3D-Area. On the other hand, in the Cloud, that feature was already implemented and is just called "Area" (see screenshot).

This feature would be very useful for calculating for example roof-Area or even building facades-area, which today, because of being 2D-Area it reports around 0 m2 (projection of points to ground).

Ilya Shevelev

  • Agisoft Technical Support
  • Newbie
  • *****
  • Posts: 49
    • View Profile
    • Agisoft Cloud
Re: Calculation of 3D-Area
« Reply #1 on: October 05, 2021, 07:34:37 PM »
Dear Sebastian,
 
The *Area* property that is automatically calculated when drawing the polygon is not a 3D area of the surface under the polygon, but an area of the polygon, projected onto the plane best fitting the polygon's vertices. This method  is good enough, when it is needed to measure an area of the vertical or oblique surface, like facade or roof, but it is not the right method if it is needed to measure the surface area of a complex object.
 
The detailed description of how all the measurements in the cloud are performed may be found in our knowledgebase: https://agisoft.freshdesk.com/support/solutions/articles/31000160891-how-to-measure-and-annotate-your-projects
 
Can you please specify if the current method provides your needs, or you need to measure the 3D area of the surface under the polygon?
 
 
Best regards,
Ilya Shevelev
Best regards,
Ilya Shevelev
Agisoft LLC

SebastianStumpf

  • Newbie
  • *
  • Posts: 8
    • View Profile
Re: Calculation of 3D-Area
« Reply #2 on: October 05, 2021, 07:47:09 PM »
Dear Ilya,

thanks for your response.

I need the implementation in Metashape: The area of the polygon projected onto its best fitting plane would be perfect. Today, only the 2D-Area is implemented in metashape, but that is not handy for measuring oblique areas.

Thanks and kind regards
Sebastian

SSP

  • Newbie
  • *
  • Posts: 1
    • View Profile
Re: Calculation of 3D-Area
« Reply #3 on: October 24, 2022, 10:32:39 PM »
I see this feature is still not implemented. Metashape can calculate the correct perimeter in 3D but then uses only the 2D surface to calculate the area instead of using the 3D surface.
May I ask what is the blocking point to calculate the surface in 3D? Other tools like Pix4D and Dronedeploy correctly do this.

« Last Edit: October 24, 2022, 10:34:24 PM by SSP »

SebastianStumpf

  • Newbie
  • *
  • Posts: 8
    • View Profile
Re: Calculation of 3D-Area
« Reply #4 on: October 26, 2022, 11:14:50 PM »
Hello SSP,

you are basically right and wrong at the same time. At the moment and to my knowledge, there is no way of measuring random 3D-Area (without a workaround, see below), BUT Agisoft is able to calculate the Area projected onto the best fitting plane of a polygon, which sometimes is even more usefull.
This means you can measure the roof area in your example by making two polygons, one for the west-facing roof side and a second for the east-facing roof side (and then add the areas of the two). The result is calculated in the field named "Area, fitted 2D". The "problem" in your example is, that the best fitting plane calculated by Agisoft in that case correlates with the XY-Plane an thus delivers the same result for 2D and fitted 2D.

When measuring a wall, like in the example that I'm attaching, you can see that the 2D-Area is basically 0 (vertical wall!), while the fitted 2D is what we would call 3D area (but projected as a 2D area to the best fitting plane) and that is the real wall-area.

Workaround: If you select only that part of the Mesh that you want to measure, then Edit --> Invert selection, then delete selection, you basically cut out all other parts of the Mesh and only leave the Roof untouched. Then you can calculate the total amount of area by using Tools --> Mesh --> Measure Area and Volume.

Feature Request: Nevertheless, you make a good point, that it would be very useful to be able to select Mesh-Faces and then be able to calculate its total 3D-Area.

Hope this helps and we get this as a new feature soon, but I do not want to miss the 2d fitted area feature!