curvature versus slope
  n = 177179 
  X=0, Y = 14.23 +/- 10.96 
  Weighted least-squares fit:  Y = 29.8 + 3.698 X  + -0.04105 X**2 

slope versus dZ, curvature < 5
  n = 51764 

  Weighted least-squares fit:  Y = 5.3 + 0.462 X  + 0.00196 X**2 
     at X = 100, Y = 71.2 
     effective RMSE xy = 111.5 

slope versus dZ, curvature < 15
  n = 96251 

  Weighted least-squares fit:  Y = 5.1 + 0.574 X  + 0.00143 X**2 

curvature versus dZ, slope < 10
  n = 48575 
  X=0, Y = 8.64 +/- 5.52 
  Weighted least-squares fit:  Y = 8.5 + 0.496 X  + 0.28215 X**2 


Number of samples 180642
Max dz = 900
Mean dz = 41
RMS dz = 94.3398113206
100cm = 88.3188848662 percentile value of dz