curvature versus slope
  n = 751770 
  X=0, Y = 51.23 +/- 23.91 
  Weighted least-squares fit:  Y = 64.7 + 1.416 X  + -0.01439 X**2 

slope versus dZ, curvature < 5
  n = 80183 

  Weighted least-squares fit:  Y = 20.8 + 1.025 X  + -0.00299 X**2 
     at X = 100, Y = 93.5 
     effective RMSE xy = 143.2 

slope versus dZ, curvature < 15
  n = 216550 

  Weighted least-squares fit:  Y = 24.5 + 0.942 X  + -0.00206 X**2 

curvature versus dZ, slope < 10
  n = 1820 
  X=0, Y = 25.19 +/- 18.18 
  Weighted least-squares fit:  Y = 27.5 + 1.622 X  + 0.04971 X**2 


Number of samples 759251
Max dz = 900
Mean dz = 82
RMS dz = 111.359777299
100cm = 70.4814349932 percentile value of dz