curvature versus slope
  n = 620716 
  X=0, Y = 48.61 +/- 28.69 
  Weighted least-squares fit:  Y = 64.7 + 1.360 X  + -0.01442 X**2 

slope versus dZ, curvature < 5
  n = 64684 

  Weighted least-squares fit:  Y = 8.0 + 0.357 X  + 0.00203 X**2 
     at X = 100, Y = 64.0 
     effective RMSE xy = 99.7 

slope versus dZ, curvature < 15
  n = 186857 

  Weighted least-squares fit:  Y = 8.4 + 0.474 X  + 0.00091 X**2 

curvature versus dZ, slope < 10
  n = 5777 
  X=0, Y = 11.09 +/- 8.04 
  Weighted least-squares fit:  Y = 9.9 + 2.572 X  + -0.02887 X**2 


Number of samples 628277
Max dz = 900
Mean dz = 50
RMS dz = 79.3914353063
100cm = 85.5592358148 percentile value of dz