curvature versus slope
  n = 5823759 
  X=0, Y = 21.05 +/- 14.85 
  Weighted least-squares fit:  Y = 39.0 + 3.310 X  + -0.03732 X**2 

slope versus dZ, curvature < 5
  n = 568497 

  Weighted least-squares fit:  Y = 17.7 + 0.060 X  + 0.00016 X**2 
     at X = 100, Y = 25.3 
     effective RMSE xy = 28.5 

slope versus dZ, curvature < 15
  n = 1245620 

  Weighted least-squares fit:  Y = 17.0 + 0.204 X  + -0.00018 X**2 

curvature versus dZ, slope < 10
  n = 250578 
  X=0, Y = 19.24 +/- 13.54 
  Weighted least-squares fit:  Y = 19.7 + 1.165 X  + 0.01594 X**2 


Number of samples 5899829
Max dz = 900
Mean dz = 38
RMS dz = 54.2770669804
100cm = 92.5599369066 percentile value of dz