curvature versus slope
  n = 1794457 
  X=0, Y = 18.03 +/- 13.42 
  Weighted least-squares fit:  Y = 51.1 + 2.561 X  + -0.02814 X**2 

slope versus dZ, curvature < 5
  n = 69698 

  Weighted least-squares fit:  Y = 55.7 + 0.134 X  + 0.00186 X**2 
     at X = 100, Y = 87.7 
     effective RMSE xy = 106.4 

slope versus dZ, curvature < 15
  n = 210585 

  Weighted least-squares fit:  Y = 54.9 + 0.269 X  + 0.00112 X**2 

curvature versus dZ, slope < 10
  n = 46478 
  X=0, Y = 63.40 +/- 35.94 
  Weighted least-squares fit:  Y = 58.7 + -0.310 X  + 0.10704 X**2 


Number of samples 1803967
Max dz = 900
Mean dz = 83
RMS dz = 109.302333003
100cm = 67.3100450285 percentile value of dz