Ground Photogrammetry -Advice needed

ExcessiveZero

Hey so the past 2 -3 weeks I have been on a photogrammetry kick and while I have had pretty good results from most things  from building facades to objects and trees I keep having consistent failures while trying to do some ground stuff, few of the pictures stitch and very often the mesh is all garbled, I know that photogrammetry has trouble with repeating patterns somewhat might be the issue its having when im trying to photograph the ground in a cylindrical manner.

So what I am wondering is if there is anything I can do to up my success rate, maybe using some kind of objects skirting the edges as markers or something ? 

Noren

Cylindrical? 

Easiest way is to make plenty of photos with enough overlap (at least two thirds so you get at least three cameras per point) more or less parallel to the ground.
If it's some tiles or other repeating pattern, you could try to add any kind of markers / unique features which are easily removable from the pictures.

ExcessiveZero

Noren said:

Cylindrical? 

Easiest way is to make plenty of photos with enough overlap (at least two thirds so you get at least three cameras per point) more or less parallel to the ground.
If it's some tiles or other repeating pattern, you could try to add any kind of markers / unique features which are easily removable from the pictures.

Yeah sorry was struggling for the word there just meant around the subject, the shooting  itself I do overlap utilizing more of a dome fashion when possible.

 I figured markers of some sort may be the way to go, my planned process is to get a photogrammetry patch bake the center down then make it tile etc in substance, so loosing the kind of skirting of the scan shouldn't be any real loss, now I just have to work out what to use for markers, maybe painted rocks lol.

rexo12

If you're shooting at a flat subject - such as  the ground, it's best to take the photos in a strafing pattern across the subject, keeping the cameras parallel with the surface. The Agisoft User manual has a nice infographic that shows how to shoot your subjects:


Just in case it's useful.

In terms of markers, tape is generally the item of choice - make little crosses of painters tape or masking tape and put them on your subject. For very rough objects that the tape won't stick to, like dirt, I guess you could use coloured pins or something like that.

Noren

Also reflections could be a problem if you shoot e. g. tiles (and the narrower your angle, the more reflection).
Since reflection is view dependent, photogrammetry programs can get easily confused by them.