curvature versus slope
  n = 480390 
  X=0, Y = 12.55 +/- 11.03 
  Weighted least-squares fit:  Y = 24.7 + 3.739 X  + -0.04123 X**2 

slope versus dZ, curvature < 5
  n = 170791 
  X=0, Y = 5.58 +/- 3.85 
  Weighted least-squares fit:  Y = 5.3 + 0.277 X  + 0.00029 X**2 
     at X = 100, Y = 35.8 
     effective RMSE xy = 55.7 

slope versus dZ, curvature < 15
  n = 251751 
  X=0, Y = 5.81 +/- 3.94 
  Weighted least-squares fit:  Y = 5.4 + 0.346 X  + 0.00036 X**2 

curvature versus dZ, slope < 10
  n = 172078 
  X=0, Y = 6.23 +/- 3.63 
  Weighted least-squares fit:  Y = 5.7 + 1.560 X  + 0.05785 X**2 


Number of samples 487308
Max dz = 900
Mean dz = 26
RMS dz = 61.9031501622
100cm = 94.2161836046 percentile value of dz