curvature versus slope
  n = 535753 
  X=0, Y = 32.98 +/- 25.21 
  Weighted least-squares fit:  Y = 61.4 + 1.634 X  + -0.01628 X**2 

slope versus dZ, curvature < 5
  n = 16022 

  Weighted least-squares fit:  Y = 8.3 + 0.055 X  + 0.00114 X**2 
     at X = 100, Y = 25.3 
     effective RMSE xy = 37.5 

slope versus dZ, curvature < 15
  n = 62448 

  Weighted least-squares fit:  Y = 8.0 + 0.201 X  + 0.00027 X**2 

curvature versus dZ, slope < 10
  n = 3545 
  X=0, Y = 8.79 +/- 3.12 
  Weighted least-squares fit:  Y = 8.7 + 0.675 X  + 0.10333 X**2 


Number of samples 541852
Max dz = 900
Mean dz = 44
RMS dz = 68.7531817446
100cm = 88.7541247425 percentile value of dz