curvature versus slope
  n = 71814 
  X=0, Y = 42.80 +/- 26.10 
  Weighted least-squares fit:  Y = 56.9 + 2.140 X  + -0.02356 X**2 

slope versus dZ, curvature < 5
  n = 27157 

  Weighted least-squares fit:  Y = 31.3 + -0.332 X  + 0.00707 X**2 
     at X = 100, Y = 68.8 
     effective RMSE xy = 96.3 

slope versus dZ, curvature < 15
  n = 45510 

  Weighted least-squares fit:  Y = 31.1 + -0.199 X  + 0.00607 X**2 

curvature versus dZ, slope < 10
  n = 4851 
  X=0, Y = 33.49 +/- 13.70 
  Weighted least-squares fit:  Y = 32.7 + 0.272 X  + 0.02195 X**2 


Number of samples 72289
Max dz = 900
Mean dz = 52
RMS dz = 145.540372406
100cm = 91.4205480779 percentile value of dz