curvature versus slope
  n = 2099700 
  X=0, Y = 19.96 +/- 14.25 
  Weighted least-squares fit:  Y = 66.0 + 1.685 X  + -0.01761 X**2 

slope versus dZ, curvature < 5
  n = 23000 

  Weighted least-squares fit:  Y = 15.1 + 0.160 X  + 0.00144 X**2 
     at X = 100, Y = 45.5 
     effective RMSE xy = 67.4 

slope versus dZ, curvature < 15
  n = 89166 

  Weighted least-squares fit:  Y = 15.2 + 0.250 X  + 0.00083 X**2 

curvature versus dZ, slope < 10
  n = 8813 
  X=0, Y = 13.57 +/- 8.79 
  Weighted least-squares fit:  Y = 13.1 + 2.534 X  + -0.09775 X**2 


Number of samples 2116597
Max dz = 900
Mean dz = 55
RMS dz = 77.9935894802
100cm = 83.7043140475 percentile value of dz