curvature versus slope
  n = 246327 
  X=0, Y = 35.53 +/- 30.04 
  Weighted least-squares fit:  Y = 57.6 + 1.932 X  + -0.01981 X**2 

slope versus dZ, curvature < 5
  n = 35224 

  Weighted least-squares fit:  Y = 28.6 + 0.734 X  + -0.00061 X**2 
     at X = 100, Y = 95.8 
     effective RMSE xy = 143.7 

slope versus dZ, curvature < 15
  n = 97026 

  Weighted least-squares fit:  Y = 29.2 + 0.686 X  + 0.00059 X**2 

curvature versus dZ, slope < 10
  n = 21443 
  X=0, Y = 36.25 +/- 17.43 
  Weighted least-squares fit:  Y = 36.9 + 0.220 X  + 0.13984 X**2 


Number of samples 248256
Max dz = 900
Mean dz = 72
RMS dz = 110.22250224
100cm = 75.2759248518 percentile value of dz