curvature versus slope
  n = 499382 
  X=0, Y = 35.03 +/- 25.08 
  Weighted least-squares fit:  Y = 62.6 + 1.640 X  + -0.01744 X**2 

slope versus dZ, curvature < 5
  n = 20359 

  Weighted least-squares fit:  Y = 15.7 + 0.342 X  + 0.00315 X**2 
     at X = 100, Y = 81.4 
     effective RMSE xy = 125.4 

slope versus dZ, curvature < 15
  n = 64595 

  Weighted least-squares fit:  Y = 16.1 + 0.430 X  + 0.00258 X**2 

curvature versus dZ, slope < 10
  n = 5262 
  X=0, Y = 14.85 +/- 10.40 
  Weighted least-squares fit:  Y = 15.3 + 2.989 X  + -0.02723 X**2 


Number of samples 507382
Max dz = 900
Mean dz = 76
RMS dz = 115.507575509
100cm = 74.2251400326 percentile value of dz