curvature versus slope
  n = 1881578 
  X=0, Y = 34.29 +/- 25.08 
  Weighted least-squares fit:  Y = 57.2 + 1.804 X  + -0.01888 X**2 

slope versus dZ, curvature < 5
  n = 63318 

  Weighted least-squares fit:  Y = 42.1 + -0.017 X  + 0.00285 X**2 
     at X = 100, Y = 68.9 
     effective RMSE xy = 85.7 

slope versus dZ, curvature < 15
  n = 239481 

  Weighted least-squares fit:  Y = 44.5 + 0.032 X  + 0.00288 X**2 

curvature versus dZ, slope < 10
  n = 18374 
  X=0, Y = 39.42 +/- 17.44 
  Weighted least-squares fit:  Y = 38.9 + 2.491 X  + -0.03418 X**2 


Number of samples 1891969
Max dz = 900
Mean dz = 75
RMS dz = 101.57263411
100cm = 73.9555986382 percentile value of dz
Mean dz (curv<=5) = 39
RMS dz (curv<=5) = 47.7388730491