Issue getting correct orhtomap

[flyworx]

Hello,

I am getting weird rendering when i run a particular set of jpg's. Site has a high structure (water tower) about 200 ft tall on it. See attached photos for reference. Any suggestions how to process data with a high/tall structures? I have need for two outputs: orhtomap and 3D mode of the structure.

Thank you so much!

Roman

[tutoss]

how looks the dense cloud of the tower?
Try set a custom value of faces of the mesh, like 100.000.000 and then create the orthophoto.

[flyworx]

Tutoss,

Most of the dense cloud points look like its underneath the ground. I will try with 100.000.000 on mesh.

See attached image.

Thank You

[tutoss]

damm... that don't look good.
What overlap do you use (longitudinal/lateral)?

In any case, beside the bad dense cloud, someone here in other post suggest (for data with a high/tall structures) classify Ground Points and then build the mesh only with the Ground Points (the mesh with that dense cloud will be bad anyway).


Aah, and for a serious work (topography, cartography, etc), you need some CGP, the final product without them will be bad, with errors on X, Y, Z, rotation and scale.

(sorry for my english)

[flyworx]

damm... that don't look good.
What overlap do you use (longitudinal/lateral)?

In any case, beside the bad dense cloud, someone here in other post suggest (for data with a high/tall structures) classify Ground Points and then build the mesh only with the Ground Points.

(sorry for my english)

Thanks. All of our photos have lon/lan coordinates baked in from the UAV and they pull from photos into photoscan. you saying get ride off lon/lan and use ground points instead?

thanks

[aggieair]

You can hand select the points that are too low or too high to clean up that point cloud before you run the mesh and texture.  Only occasionally do I get a perfect point cloud that does not require any editing. 

You can also use the classify ground points tool so that the water tower is not included in your DEM creation (when you make mesh, change the point category).  This is what tutoss is saying.  It turns all the ground points brown (based on some settings you chose), then you make the mesh on ground points only.

If you do add ground control points, then you uncheck all your lat/long cameras or it will mess up the solution.  Also update the projection if you add control points.

[tutoss]

these lon/lan coordinates from any uav are not accurate (error in meters). A proper CGP are accurate in milimeters.

Anyway, if you fly again, fly higher and take more frecuent photos, so you get a higher overlap of the tower, and then you can combine both flights and align them on PhotoScan.

[flyworx]

I will give it a try with both of your suggestions. thank you!!

[tutoss]

Example:
Use of CGP vs camera position only for georeferencing:

CGP only:



cameras positions only:


diference (transparent is camera positions only):


(use the horizontal bar)

[aggieair]

 n/a

[HyperFox]

I do not think that the problem is only the absence of gcp.
First of all, the dense point cloud show a lot of noise.
Too much for my humble opinion.

The surface is very light and has not much texture. This makes it difficult to match identical points in different images.
And this process depends highly on you image wuality. Which camera are you using? Perhaps this could be an issue?

[tutoss]

the use of GCP is a recomendation, is not the source of the problem.