curvature versus slope
  n = 732050 
  X=0, Y = 13.68 +/- 10.61 
  Weighted least-squares fit:  Y = 37.7 + 3.368 X  + -0.03812 X**2 

slope versus dZ, curvature < 5
  n = 122852 

  Weighted least-squares fit:  Y = 58.5 + 0.282 X  + -0.00029 X**2 
     at X = 100, Y = 83.9 
     effective RMSE xy = 94.4 

slope versus dZ, curvature < 15
  n = 224486 

  Weighted least-squares fit:  Y = 59.1 + 0.172 X  + 0.00196 X**2 

curvature versus dZ, slope < 10
  n = 137708 
  X=0, Y = 59.27 +/- 33.90 
  Weighted least-squares fit:  Y = 59.5 + 0.476 X  + -0.01370 X**2 


Number of samples 736165
Max dz = 900
Mean dz = 75
RMS dz = 104.067285926
100cm = 76.1124204492 percentile value of dz