Orthomosaic Artefacts How-Too

[GrinGEO]

Im wondering why I have such artefacts in my Ortomosaic and how I could improve it....

I flew at about 160m high and in the pics I don´t have any artefacts... only in the Agisoft output...

[GrinGEO]

The problems are especially in the roof parts of buildings.... there Agisoft seems to combine different pics in the wrong way causing roof borders that are not in a line.... any help on this?

[stihl]

The artefacts are due to incomplete geometry on the edges of your building rooves. Because the default build Orthomosaic relies on using the all of the points of the dense point clouds, any missing geometry there will result in artefacts in the Ortho.

To overcome this you will need to rebuild a new DEM that's only using the Ground points. The first step is to run the automatic ground classification tool and then only choose Ground in the Build DEM window.

Then rebuild your Orthomosaic based on the DEM (instead of the Mesh). When it's finished go to the Orthomosaic Viewer and you will notice that the artefacts are gone but now you will have to deal with building lean. You will have to manually edit the Orthomosaic by placing polygons around objects (such as buildings) and manually choosing an aesthetically pleasing photo by right clicking the polygon and choosing Assign images.

When you're finished, use the button on the toolbar to Update the Orthomosaic and export it as a new TIFF file.

[SAV]

Hi GrinGEO,

Try to increase the forward and side overlap when capturing your aerial photographs. Moreover, slightly oblique imagery (instead of nadir) might help to improve reconstruction results as well.

You'll need to generate a 'high quality' DEM in order to compute a good orthophotograph (the DEM is used to undistort your images).

Regards
SAV

[GrinGEO]

Thanks for helping... I had a 80% forward + 60% side overlap. Im reprocessing the same area now with cross grid scanning...
Also im processing the Dense Cloud in High settings...

But Stihl Feedback seems to be very very interesint and should be the way to go... since he is right, the Ortho needs to be processsed only on ground points and not on roofs...

[cioro]

You can try also to use a decimated mesh for the ortophoto build stage. If you have a good side/frontal overlap, let's say 70% for both, you can try also the following steps:
-  build dense cloud on high settings
-  build mesh
- decimate mesh and build ortophoto (try & see) until you are satisfied
Normally you'll not need any manual selection of the photos

[GrinGEO]

I would prefer not to use high dense cloud. It takes too long for calculation (over 18 hours) and generates about 1 Billion Points

[GrinGEO]

Thansk Stihl way is almost perfect. I have a very good Orthofoto. But now I have a few, but really strong misalignements... Is there any way to chose on the Orthofoto to use a different picture in some parts?

In the Point cloud I fave a very good point quality with almost perfect alignment... Only the Ortho result could be a bit petter