curvature versus slope
  n = 154384 
  X=0, Y = 28.31 +/- 13.53 
  Weighted least-squares fit:  Y = 44.7 + 2.929 X  + -0.03305 X**2 

slope versus dZ, curvature < 5
  n = 30715 

  Weighted least-squares fit:  Y = 28.8 + -0.142 X  + 0.00988 X**2 
     at X = 100, Y = 113.4 
     effective RMSE xy = 172.3 

slope versus dZ, curvature < 15
  n = 62807 

  Weighted least-squares fit:  Y = 23.7 + 0.230 X  + 0.00663 X**2 

curvature versus dZ, slope < 10
  n = 1019 
  X=0, Y = 35.14 +/- 15.96 
  Weighted least-squares fit:  Y = 35.5 + -0.675 X  + 0.09781 X**2 


Number of samples 156242
Max dz = 900
Mean dz = 70
RMS dz = 119.682914403
100cm = 77.4561257536 percentile value of dz