curvature versus slope
  n = 129082 
  X=0, Y = 24.06 +/- 19.82 
  Weighted least-squares fit:  Y = 48.8 + 2.474 X  + -0.02665 X**2 

slope versus dZ, curvature < 5
  n = 16502 

  Weighted least-squares fit:  Y = 56.8 + 0.065 X  + 0.00127 X**2 
     at X = 100, Y = 76.0 
     effective RMSE xy = 79.2 

slope versus dZ, curvature < 15
  n = 34102 

  Weighted least-squares fit:  Y = 54.7 + 0.124 X  + 0.00199 X**2 

curvature versus dZ, slope < 10
  n = 11198 
  X=0, Y = 64.72 +/- 33.99 
  Weighted least-squares fit:  Y = 59.6 + -3.040 X  + 0.26824 X**2 


Number of samples 130604
Max dz = 900
Mean dz = 78
RMS dz = 131.251666656
100cm = 74.9464028667 percentile value of dz