curvature versus slope
  n = 321432 
  X=0, Y = 30.83 +/- 17.04 
  Weighted least-squares fit:  Y = 41.2 + 2.537 X  + -0.02658 X**2 

slope versus dZ, curvature < 5
  n = 42712 

  Weighted least-squares fit:  Y = 9.6 + 0.849 X  + -0.00261 X**2 
     at X = 100, Y = 68.4 
     effective RMSE xy = 106.3 

slope versus dZ, curvature < 15
  n = 116214 

  Weighted least-squares fit:  Y = 10.1 + 0.877 X  + -0.00262 X**2 

curvature versus dZ, slope < 10
  n = 9768 
  X=0, Y = 15.37 +/- 10.12 
  Weighted least-squares fit:  Y = 13.3 + 2.404 X  + 0.03603 X**2 


Number of samples 323733
Max dz = 900
Mean dz = 55
RMS dz = 106.667708328
100cm = 85.5726787198 percentile value of dz