curvature versus slope
  n = 3358981 
  X=0, Y = 18.15 +/- 9.26 
  Weighted least-squares fit:  Y = 49.0 + 2.528 X  + -0.02753 X**2 

slope versus dZ, curvature < 5
  n = 135111 

  Weighted least-squares fit:  Y = 10.9 + 0.473 X  + -0.00234 X**2 
     at X = 100, Y = 34.8 
     effective RMSE xy = 51.9 

slope versus dZ, curvature < 15
  n = 516628 

  Weighted least-squares fit:  Y = 13.0 + 0.403 X  + -0.00078 X**2 

curvature versus dZ, slope < 10
  n = 25836 
  X=0, Y = 13.76 +/- 8.05 
  Weighted least-squares fit:  Y = 14.3 + 1.890 X  + -0.08988 X**2 


Number of samples 3399610
Max dz = 800
Mean dz = 40
RMS dz = 57.6888204074
100cm = 92.0008177409 percentile value of dz