Agisoft Metashape

Agisoft Metashape => General => Topic started by: tuffi on June 19, 2019, 12:14:51 PM

Title: Effects of the quality of dense cloud generation
Post by: tuffi on June 19, 2019, 12:14:51 PM
Hi,

someone can better explain the effects of the  quality parameters of the dense cloud in the final results?

Actually I perform some survey but i am located in a remote area with only a budget level notebook so I can't use medium or high parameters.

Geometry of the site is quite simple.
If I use Low and Lowest parameters to generate dense cloud: this will have effects only on the DEM resolution  or also on the quality of the geometrical recostruction?

Thank you..
Title: Re: Effects of the quality of dense cloud generation
Post by: stihl on June 19, 2019, 05:42:42 PM
Changing the quality level from High to Medium to Low changes the resolution of the input images.
If you select Medium, Photoscan will first downscale the images to 1/4th of their original resolution. 1/4th of the original pixels available results in a dense point cloud with 1/4th of the amount of points when compared to processing the project on High.

Per Image Side Downsample Factor                               Per Image scaling            Expected point density
Ultra High Quality:                          1:1                                      1:1                                             GSD        1:1
High Quality                                        1:2                                      1:4                                             GSD        1:2
Medium Quality                                1:4                                      1:16                                          GSD        1:4
Low Quality                                         1:8                                      1:64                                          GSD        1:8
Lowest Quality                                  1:16                                   1:256                                       GSD        1:16

Example: If Ultra high produces 100 million points, Medium quality will then create 25 million points.
If your project GSD is 2 cm/pixel, your maximum DEM resolution at Ultra high will be 2 cm/pixel. At Medium it will be 8 cm/pixel.

If Photoscan has to work with lower resolution images to create the dense cloud (and geometry of objects), then this will have an impact on the quality of the reconstructed geometry. It's best to make a small bounding box in your project area and test different quality levels to see if the low quality parameter provides you with the level of detail you're looking for.