curvature versus slope
  n = 4190194 
  X=0, Y = 6.30 +/- 4.93 
  Weighted least-squares fit:  Y = 4.8 + 4.566 X  + -0.04890 X**2 

slope versus dZ, curvature < 5
  n = 3154003 
  X=0, Y = 3.63 +/- 2.44 
  Weighted least-squares fit:  Y = 3.6 + 0.114 X  + 0.00191 X**2 
     at X = 100, Y = 34.1 
     effective RMSE xy = 53.3 

slope versus dZ, curvature < 15
  n = 4013051 
  X=0, Y = 3.86 +/- 2.64 
  Weighted least-squares fit:  Y = 4.0 + 0.119 X  + 0.00199 X**2 

curvature versus dZ, slope < 10
  n = 3791921 
  X=0, Y = 3.73 +/- 2.52 
  Weighted least-squares fit:  Y = 3.3 + 1.252 X  + -0.03451 X**2 


Number of samples 4196197
Max dz = 900
Mean dz = 4
RMS dz = 16.0934769394
100cm = 99.8547970937 percentile value of dz
Mean dz (curv<=5) = 3
RMS dz (curv<=5) = 5.19615242271