curvature versus slope
  n = 792821 
  X=0, Y = 7.12 +/- 6.14 
  Weighted least-squares fit:  Y = 6.7 + 5.200 X  + -0.06722 X**2 

slope versus dZ, curvature < 5
  n = 606991 
  X=0, Y = 6.95 +/- 4.95 
  Weighted least-squares fit:  Y = 7.7 + 0.285 X  + 0.00034 X**2 
     at X = 100, Y = 39.6 
     effective RMSE xy = 61.1 

slope versus dZ, curvature < 15
  n = 743190 
  X=0, Y = 6.94 +/- 4.90 
  Weighted least-squares fit:  Y = 7.9 + 0.396 X  + -0.00091 X**2 

curvature versus dZ, slope < 10
  n = 637500 
  X=0, Y = 7.82 +/- 5.81 
  Weighted least-squares fit:  Y = 7.1 + 2.550 X  + -0.04958 X**2 


Number of samples 794689
Max dz = 600
Mean dz = 9
RMS dz = 15.2970585408
100cm = 99.7269372044 percentile value of dz