curvature versus slope
  n = 666317 
  X=0, Y = 29.86 +/- 25.13 
  Weighted least-squares fit:  Y = 76.5 + 1.010 X  + -0.00932 X**2 

slope versus dZ, curvature < 5
  n = 4397 

  Weighted least-squares fit:  Y = 8.9 + -0.046 X  + 0.00150 X**2 
     at X = 100, Y = 19.2 
     effective RMSE xy = 26.8 

slope versus dZ, curvature < 15
  n = 12572 

  Weighted least-squares fit:  Y = 4.2 + 0.466 X  + -0.00104 X**2 

curvature versus dZ, slope < 10
  n = 2255 
  X=0, Y = 7.17 +/- 4.62 
  Weighted least-squares fit:  Y = 6.6 + 1.508 X  + -0.07599 X**2 


Number of samples 679908
Max dz = 900
Mean dz = 63
RMS dz = 89.0224690738
100cm = 79.5762073692 percentile value of dz