Setting Z plane without co-ordinates but with markers

[Sam95]

Hi there,

I have built a few models on Agisoft using a local co-ordinate system, I have markers within these models, 3 on the left, 3 on the right, I have used these to create a scale within my model, but when it comes to constructing the DEM, it clearly is being affected by the slope that Agisoft has assigned to my model. Is there a way to use these markers to make the model flat on the Z plane?

I have tried to use "imaginary co-ordinates", the reference setting already says local co-ordinates, so I added 4 more markers (I call them GCP's) on  the flat pieces or corners of my model, and within the reference pane I have given them X, Y, Z co-ordinates of (0,0,0), (0,1,0), (1,0,0) and (1,1,0), but that didn't seem to do anything to my model, the XYZ values for my other markers also didn't change at all which I'm sure they would if my new points altered anything.  When I build the DEM again following these steps, using geographic, nothing has changed. I tried to build it on planar using the new markers (GCP's) as reference and it appears to have flipped my model somehow, the highest point is now the lowest and lowest the highest.

I have rotated my object now along the grid, which has helped the DEM slope in geographic, but still flips my model on planar, I need a more accurate fix where I can set my markers to 0 on the z axis?

Any help would be appreciated.

[Alexey Pasumansky]

Hello Sam95,

After adding markers with the "imaginary" coordinates you need to check on these markers in the Reference pane, uncheck all other markers in the pane and press Update button on the pane's toolbar. Of course, the coordinate system in the Reference pane setting dialog should be set to "Local Coordinates" beforehand (otherwise, these coordinates would be considered as coordinates of some geographic coordinates which would lead to the incorrect interpretation and therefore wrong model orientation.

Another way is just to add markers on the plain surface without coordinates, and use them to set up the projection plane definition "by markers" in the Build DEM dialog for Planar option.

[Sam95]

Hi there Alexey,

Thank you, my only problem is I have two scale bars that i've made and used to scale my model, I do not know the distance between these two scale bars, only the distance between markers on my scale bars, so I thought to only alter the z plane and leave the x and y as they are instead of imaginary x y and z values, but I am worried that altering the z plane alone will alter the scale of my model?


When I use the second option you have suggested, using planar for DEM construction, my orthophotos fail to construct properly and usually end up blank.

[Alexey Pasumansky]

Hello Sam95,

I think when you are following the second approach (applying the scale to the model via scale bars and defining the projection plane via two marker pairs) the order of the markers in one of the two pairs is set up incorrectly. Can you try to change the order in one pair only and see, if the orthomosaic is properly displayed then?

[Sam95]

Hi Alexey,

I'm not sure I understand,

So when I am in the build DEM settings, in the planar option,

I am unsure of what order you mean? There is the projection plane set to markers, and then Horizontal axis, where you can in put two markers, (usually I add one marker from each of my two scale bars) as  I see that as the horizontal plane, you have to select horizontal or vertical so I assume the markers shown in the boxes for vertical axis have no impact f I select horizontal?

Thank you for your help

[Alexey Pasumansky]

Hello Sam95,

The order of marker labels in each pair that you define for the Planar projection define the "face" side of the plane. I think in your case (when you get empty orthomosaic) it is inverted, so I suggest to change the order for one of the marker pairs, i.e instead of "point 1" -> "point 2" use "point 2" ->  "point 1".