curvature versus slope
  n = 495224 
  X=0, Y = 29.12 +/- 14.35 
  Weighted least-squares fit:  Y = 29.5 + 3.188 X  + -0.03355 X**2 

slope versus dZ, curvature < 5
  n = 126509 

  Weighted least-squares fit:  Y = 3.7 + 1.146 X  + -0.00491 X**2 
     at X = 100, Y = 69.2 
     effective RMSE xy = 108.5 

slope versus dZ, curvature < 15
  n = 314754 

  Weighted least-squares fit:  Y = 4.8 + 1.123 X  + -0.00437 X**2 

curvature versus dZ, slope < 10
  n = 23099 
  X=0, Y = 12.26 +/- 8.39 
  Weighted least-squares fit:  Y = 10.6 + 2.677 X  + -0.07815 X**2 


Number of samples 502799
Max dz = 900
Mean dz = 37
RMS dz = 64.3272881443
100cm = 94.1219055726 percentile value of dz