curvature versus slope
  n = 574649 
  X=0, Y = 33.37 +/- 17.58 
  Weighted least-squares fit:  Y = 37.8 + 2.606 X  + -0.02710 X**2 

slope versus dZ, curvature < 5
  n = 100422 

  Weighted least-squares fit:  Y = 7.7 + 0.954 X  + -0.00234 X**2 
     at X = 100, Y = 79.7 
     effective RMSE xy = 124.7 

slope versus dZ, curvature < 15
  n = 265567 

  Weighted least-squares fit:  Y = 8.5 + 0.966 X  + -0.00231 X**2 

curvature versus dZ, slope < 10
  n = 16160 
  X=0, Y = 16.30 +/- 9.55 
  Weighted least-squares fit:  Y = 14.5 + 1.826 X  + 0.04497 X**2 


Number of samples 581300
Max dz = 900
Mean dz = 46
RMS dz = 72.3187389271
100cm = 89.645621882 percentile value of dz