curvature versus slope
  n = 226611 
  X=0, Y = 54.13 +/- 25.62 
  Weighted least-squares fit:  Y = 67.6 + 1.369 X  + -0.01475 X**2 

slope versus dZ, curvature < 5
  n = 53747 

  Weighted least-squares fit:  Y = 12.0 + 0.636 X  + -0.00098 X**2 
     at X = 100, Y = 65.8 
     effective RMSE xy = 101.6 

slope versus dZ, curvature < 15
  n = 109122 

  Weighted least-squares fit:  Y = 13.2 + 0.674 X  + -0.00109 X**2 

curvature versus dZ, slope < 10
  n = 2183 
  X=0, Y = 18.91 +/- 11.01 
  Weighted least-squares fit:  Y = 17.0 + 2.899 X  + -0.09266 X**2 


Number of samples 232101
Max dz = 900
Mean dz = 63
RMS dz = 96.5090669316
100cm = 85.1556003636 percentile value of dz