curvature versus slope
  n = 233001 
  X=0, Y = 31.26 +/- 17.44 
  Weighted least-squares fit:  Y = 45.9 + 2.653 X  + -0.02851 X**2 

slope versus dZ, curvature < 5
  n = 104104 

  Weighted least-squares fit:  Y = 42.3 + -0.237 X  + 0.00418 X**2 
     at X = 100, Y = 60.5 
     effective RMSE xy = 67.8 

slope versus dZ, curvature < 15
  n = 157028 

  Weighted least-squares fit:  Y = 42.7 + -0.160 X  + 0.00337 X**2 

curvature versus dZ, slope < 10
  n = 10517 
  X=0, Y = 40.73 +/- 8.28 
  Weighted least-squares fit:  Y = 40.5 + 3.483 X  + -0.14653 X**2 


Number of samples 234737
Max dz = 900
Mean dz = 47
RMS dz = 82.7163828996
100cm = 93.7372463651 percentile value of dz