curvature versus slope
  n = 1961467 
  X=0, Y = 29.58 +/- 24.16 
  Weighted least-squares fit:  Y = 60.0 + 1.713 X  + -0.01816 X**2 

slope versus dZ, curvature < 5
  n = 59289 

  Weighted least-squares fit:  Y = 5.1 + 0.231 X  + -0.00035 X**2 
     at X = 100, Y = 24.7 
     effective RMSE xy = 38.0 

slope versus dZ, curvature < 15
  n = 238273 

  Weighted least-squares fit:  Y = 5.9 + 0.258 X  + -0.00032 X**2 

curvature versus dZ, slope < 10
  n = 29017 
  X=0, Y = 6.31 +/- 3.33 
  Weighted least-squares fit:  Y = 4.5 + 2.376 X  + -0.04033 X**2 


Number of samples 1998200
Max dz = 700
Mean dz = 35
RMS dz = 53.8794951721
100cm = 92.7204984486 percentile value of dz