curvature versus slope
  n = 828811 
  X=0, Y = 4.13 +/- 2.41 
  Weighted least-squares fit:  Y = 2.0 + 4.451 X  + -0.04711 X**2 

slope versus dZ, curvature < 5
  n = 660655 
  X=0, Y = 7.28 +/- 4.45 
  Weighted least-squares fit:  Y = 6.0 + 0.362 X  + -0.00162 X**2 
     at X = 100, Y = 26.0 
     effective RMSE xy = 39.7 

slope versus dZ, curvature < 15
  n = 810545 
  X=0, Y = 7.52 +/- 4.67 
  Weighted least-squares fit:  Y = 6.0 + 0.435 X  + -0.00204 X**2 

curvature versus dZ, slope < 10
  n = 789135 
  X=0, Y = 6.88 +/- 4.33 
  Weighted least-squares fit:  Y = 6.3 + 1.201 X  + 0.05250 X**2 


Number of samples 828882
Max dz = 200
Mean dz = 6
RMS dz = 8.60232526704
100cm = 99.9915548896 percentile value of dz