curvature versus slope
  n = 700054 
  X=0, Y = 43.56 +/- 19.41 
  Weighted least-squares fit:  Y = 49.3 + 2.338 X  + -0.02496 X**2 

slope versus dZ, curvature < 5
  n = 76964 

  Weighted least-squares fit:  Y = 45.1 + 1.234 X  + -0.00712 X**2 
     at X = 100, Y = 97.4 
     effective RMSE xy = 135.5 

slope versus dZ, curvature < 15
  n = 251992 

  Weighted least-squares fit:  Y = 44.2 + 1.206 X  + -0.00630 X**2 

curvature versus dZ, slope < 10
  n = 6229 
  X=0, Y = 57.88 +/- 31.68 
  Weighted least-squares fit:  Y = 56.6 + -0.501 X  + 0.04165 X**2 


Number of samples 705563
Max dz = 900
Mean dz = 81
RMS dz = 107.219401229
100cm = 68.321609835 percentile value of dz