curvature versus slope
  n = 157229 
  X=0, Y = 25.61 +/- 20.57 
  Weighted least-squares fit:  Y = 51.8 + 2.479 X  + -0.02712 X**2 

slope versus dZ, curvature < 5
  n = 40361 

  Weighted least-squares fit:  Y = 23.7 + 0.642 X  + 0.00331 X**2 
     at X = 100, Y = 120.9 
     effective RMSE xy = 186.3 

slope versus dZ, curvature < 15
  n = 74947 

  Weighted least-squares fit:  Y = 24.4 + 0.672 X  + 0.00359 X**2 

curvature versus dZ, slope < 10
  n = 24312 
  X=0, Y = 26.19 +/- 14.36 
  Weighted least-squares fit:  Y = 27.3 + 3.152 X  + -0.17942 X**2 


Number of samples 159774
Max dz = 900
Mean dz = 75
RMS dz = 120.904921323
100cm = 75.2537959868 percentile value of dz