curvature versus slope
  n = 89866 
  X=0, Y = 33.52 +/- 24.08 
  Weighted least-squares fit:  Y = 54.1 + 2.128 X  + -0.02199 X**2 

slope versus dZ, curvature < 5
  n = 7965 

  Weighted least-squares fit:  Y = 90.4 + -0.192 X  + 0.00193 X**2 
     at X = 100, Y = 90.5 
     effective RMSE xy = 5.1 

slope versus dZ, curvature < 15
  n = 20294 

  Weighted least-squares fit:  Y = 89.9 + -0.170 X  + 0.00348 X**2 

curvature versus dZ, slope < 10
  n = 2306 
  X=0, Y = 89.34 +/- 13.99 
  Weighted least-squares fit:  Y = 90.7 + -2.481 X  + 0.14652 X**2 


Number of samples 90661
Max dz = 900
Mean dz = 102
RMS dz = 161.959871573
100cm = 60.6843074751 percentile value of dz