curvature versus slope
  n = 682901 
  X=0, Y = 19.03 +/- 16.36 
  Weighted least-squares fit:  Y = 46.8 + 2.584 X  + -0.02878 X**2 

slope versus dZ, curvature < 5
  n = 81753 

  Weighted least-squares fit:  Y = 9.3 + 0.451 X  + 0.00135 X**2 
     at X = 100, Y = 67.8 
     effective RMSE xy = 105.5 

slope versus dZ, curvature < 15
  n = 167987 

  Weighted least-squares fit:  Y = 8.7 + 0.581 X  + 0.00044 X**2 

curvature versus dZ, slope < 10
  n = 80406 
  X=0, Y = 12.11 +/- 7.68 
  Weighted least-squares fit:  Y = 10.7 + 1.724 X  + 0.03306 X**2 


Number of samples 696060
Max dz = 900
Mean dz = 56
RMS dz = 88.1532756056
100cm = 82.0582995719 percentile value of dz