curvature versus slope
  n = 505983 
  X=0, Y = 49.65 +/- 31.64 
  Weighted least-squares fit:  Y = 69.1 + 1.537 X  + -0.01644 X**2 

slope versus dZ, curvature < 5
  n = 71523 

  Weighted least-squares fit:  Y = 28.3 + 0.239 X  + 0.00376 X**2 
     at X = 100, Y = 89.8 
     effective RMSE xy = 133.9 

slope versus dZ, curvature < 15
  n = 218127 

  Weighted least-squares fit:  Y = 24.3 + 0.494 X  + 0.00235 X**2 

curvature versus dZ, slope < 10
  n = 11365 
  X=0, Y = 35.37 +/- 17.66 
  Weighted least-squares fit:  Y = 35.2 + 1.219 X  + -0.12951 X**2 


Number of samples 514495
Max dz = 900
Mean dz = 67
RMS dz = 94.1063228481
100cm = 77.3280595535 percentile value of dz
Mean dz (curv<=5) = 43
RMS dz (curv<=5) = 58.7877538268