curvature versus slope
  n = 580547 
  X=0, Y = 36.14 +/- 17.21 
  Weighted least-squares fit:  Y = 47.7 + 2.465 X  + -0.02753 X**2 

slope versus dZ, curvature < 5
  n = 190499 

  Weighted least-squares fit:  Y = 32.6 + 1.415 X  + -0.00818 X**2 
     at X = 100, Y = 92.3 
     effective RMSE xy = 135.6 

slope versus dZ, curvature < 15
  n = 313625 

  Weighted least-squares fit:  Y = 34.0 + 1.329 X  + -0.00740 X**2 

curvature versus dZ, slope < 10
  n = 15680 
  X=0, Y = 39.50 +/- 20.99 
  Weighted least-squares fit:  Y = 39.6 + 1.328 X  + 0.07664 X**2 


Number of samples 589916
Max dz = 900
Mean dz = 72
RMS dz = 92.7954740276
100cm = 72.453366242 percentile value of dz