curvature versus slope
  n = 601357 
  X=0, Y = 36.76 +/- 26.52 
  Weighted least-squares fit:  Y = 57.2 + 1.718 X  + -0.01877 X**2 

slope versus dZ, curvature < 5
  n = 34355 

  Weighted least-squares fit:  Y = 14.5 + 0.087 X  + 0.00270 X**2 
     at X = 100, Y = 50.1 
     effective RMSE xy = 75.4 

slope versus dZ, curvature < 15
  n = 105269 

  Weighted least-squares fit:  Y = 15.2 + 0.144 X  + 0.00231 X**2 

curvature versus dZ, slope < 10
  n = 10398 
  X=0, Y = 16.55 +/- 12.61 
  Weighted least-squares fit:  Y = 14.6 + 1.934 X  + -0.00338 X**2 


Number of samples 607492
Max dz = 800
Mean dz = 51
RMS dz = 74.4311762637
100cm = 84.9976625207 percentile value of dz