curvature versus slope
  n = 1025450 
  X=0, Y = 15.25 +/- 11.25 
  Weighted least-squares fit:  Y = 20.7 + 4.322 X  + -0.04956 X**2 

slope versus dZ, curvature < 5
  n = 425303 
  X=0, Y = 32.85 +/- 6.05 
  Weighted least-squares fit:  Y = 28.3 + -0.014 X  + 0.00339 X**2 
     at X = 100, Y = 60.7 
     effective RMSE xy = 84.4 

slope versus dZ, curvature < 15
  n = 685474 
  X=0, Y = 32.85 +/- 6.05 
  Weighted least-squares fit:  Y = 27.0 + 0.146 X  + 0.00297 X**2 

curvature versus dZ, slope < 10
  n = 420086 
  X=0, Y = 28.24 +/- 13.60 
  Weighted least-squares fit:  Y = 28.6 + -0.592 X  + 0.20195 X**2 


Number of samples 1045265
Max dz = 900
Mean dz = 40
RMS dz = 65.1843539509
100cm = 92.2932462103 percentile value of dz