curvature versus slope
  n = 1543357 
  X=0, Y = 16.90 +/- 11.92 
  Weighted least-squares fit:  Y = 35.6 + 3.139 X  + -0.03557 X**2 

slope versus dZ, curvature < 5
  n = 269124 

  Weighted least-squares fit:  Y = 10.6 + 1.321 X  + -0.00536 X**2 
     at X = 100, Y = 89.1 
     effective RMSE xy = 139.0 

slope versus dZ, curvature < 15
  n = 516970 

  Weighted least-squares fit:  Y = 11.4 + 1.464 X  + -0.00686 X**2 

curvature versus dZ, slope < 10
  n = 188448 
  X=0, Y = 17.04 +/- 13.72 
  Weighted least-squares fit:  Y = 17.3 + 3.464 X  + -0.12252 X**2 


Number of samples 1566700
Max dz = 900
Mean dz = 61
RMS dz = 87.7268487978
100cm = 79.2015063509 percentile value of dz