curvature versus slope
  n = 3249466 
  X=0, Y = 6.05 +/- 3.37 
  Weighted least-squares fit:  Y = 4.4 + 0.713 X  + 0.00455 X**2 

slope versus dZ, curvature < 5
  n = 578237 
  X=0, Y = 5.76 +/- 3.56 
  Weighted least-squares fit:  Y = 5.1 + 0.070 X  + 0.00053 X**2 
     at X = 100, Y = 17.5 
     effective RMSE xy = 26.2 

slope versus dZ, curvature < 15
  n = 1469934 
  X=0, Y = 5.45 +/- 3.33 
  Weighted least-squares fit:  Y = 5.0 + 0.111 X  + 0.00015 X**2 

curvature versus dZ, slope < 10
  n = 2827173 
  X=0, Y = 5.34 +/- 3.35 
  Weighted least-squares fit:  Y = 5.0 + 0.183 X  + 0.00216 X**2 


Number of samples 3249786
Max dz = 900
Mean dz = 5
RMS dz = 8.12403840464
100cm = 99.9894454589 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 5.38516480713