laz export pointcloud coordinate precision degraded (2.1.3)

[andyroo]

I am comparing two processing methods (masked and unmasked aerial obliques). I have a problem where point clouds generated from the masked images export with _sometimes_ lower coordinate precision than the unmasked images in 2.1.3.

For the unmasked images, 12 of 12 flights were exported with cm precision, but for the masked flights, only 3 of 12 were exported with cm precision, and the others had xyz rounded to the decimeter. This makes it impossible (or very much harder) for me to calculate the relative accuracy of the two methods by comparing their surfaces.

Is there any way I can export images with cm precision by upgrading or downgrading Metashape without re-aligning and regenerating dense clouds? Currently using version 2.1.3. I figured out that I could downgrade to 2.1.0 and export the dense cloud with centimeter precision in that version, but going forward, I would love to be able to control this in 2.2.x so that I can compare multiple 4D-aligned flights without having to worry about variable precision that I can't control in export.

I understand from this post (LAS Export rounds all points to the centimetre) that export precision and calculated coordinate precision are a function of GSD and depth map quality used. Since I used the all the same settings except masking, I think that maybe the issue is that because I masked the near-field (water) in the oblique imagery, Metashape calculated a larger GSD?

Both projects (masked and unmasked) were created from the same template, and the only difference is that one had masks loaded before alignment, and was aligned with key point masks enabled.

Below is output from lasinfo showing the precision issue - this is on raw pointclouds exported from Metashape.

Code: [Select]

project\outputs\laz\12flt\*.laz -no_check 2>&1|findstr "factor lasinfo"
lasinfo (240319) report for 'project\outputs\laz\12flt\20160928_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20170301_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20171227_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20180123_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20180329_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20180913_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20200506_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20200918_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20220302_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20220928_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20230308_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt\20231012_Ru10Pa3Re0_3_align_60k_unguided.laz'
  scale factor x y z:         0.01 0.01 0.01

project\outputs\laz\12flt_mask\*.laz -no_check 2>&1|findstr "factor lasinfo"
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20160928_kp_masked.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20170301_kp_masked.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20171227_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20180123_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20180329_kp_masked.laz'
  scale factor x y z:         0.01 0.01 0.01
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20180913_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20200506_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20200918_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20220302_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20220928_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20230308_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1
lasinfo (240319) report for 'project\outputs\laz\12flt_mask\20230312_kp_masked.laz'
  scale factor x y z:         0.1 0.1 0.1

[vineg]

Hi!

Since version 2.1.4 it is possible to set precision for the point cloud export using a tweak ExportPointCloud/precision
You can set it in Tools menu -> Preferences... -> Advanced -> Tweaks...
Use 0.01 value for centimeter precision.

Regards, Egor

[andyroo]

Hi!

Since version 2.1.4 it is possible to set precision for the point cloud export using a tweak ExportPointCloud/precision
You can set it in Tools menu -> Preferences... -> Advanced -> Tweaks...
Use 0.01 value for centimeter precision.

Regards, Egor

PERFECT! Thanks for that tip!