curvature versus slope
  n = 505575 
  X=0, Y = 67.49 +/- 26.37 
  Weighted least-squares fit:  Y = 75.2 + 0.869 X  + -0.00770 X**2 

slope versus dZ, curvature < 5
  n = 2188 

  Weighted least-squares fit:  Y = 2.8 + 0.634 X  + -0.00234 X**2 
     at X = 100, Y = 42.7 
     effective RMSE xy = 67.0 

slope versus dZ, curvature < 15
  n = 16395 

  Weighted least-squares fit:  Y = 11.6 + 0.441 X  + -0.00112 X**2 

curvature versus dZ, slope < 10
  n = 128 
  X=0, Y = 8.06 +/- 1.42 
  Weighted least-squares fit:  Y = 8.4 + 3.841 X  + -0.13433 X**2 


Number of samples 510373
Max dz = 900
Mean dz = 53
RMS dz = 75.9473501842
100cm = 85.6951680438 percentile value of dz