点云

Chamfer Distance §

$$\text{d}(A,B)=\sum _A\underset{B}{\min }||a-b|{|}^2+\sum _B\underset{A}{\min }||a-b|{|}^2$$

A 点集每个点找 B点集内最近点的距离求和 + …

Hausdorff distance §

1. Directed Non-Symmetric

$$\text{h}(\text{A},\text{B})=\underset{A}{\max }(\underset{B}{\min }(||a-b||))$$

2. Symmetry

$$\text{H}(\text{A},\text{B})=\max (\text{h}(\text{A},\text{B}),\text{h}(\text{B},\text{A}))$$

找到 B 点集每一个到 A 点集最近的点对, 然后取出这些点对的最大距离

LASzip §

• write header (uncompressed)
• *write points in “chunks” of 50,000
  • store first point raw (uncompressed)
  • compress next point
    • predict attributes that have changed
      • return number, intensity, scan angle, …
    • predict coordinates using $\Delta x$, $\Delta y$, $z$
    • treat GPS time as integer, predict steps