curvature versus slope
  n = 378842 
  X=0, Y = 35.41 +/- 23.63 
  Weighted least-squares fit:  Y = 60.2 + 1.661 X  + -0.01803 X**2 

slope versus dZ, curvature < 5
  n = 42905 

  Weighted least-squares fit:  Y = 10.8 + 0.120 X  + 0.00419 X**2 
     at X = 100, Y = 64.7 
     effective RMSE xy = 100.2 

slope versus dZ, curvature < 15
  n = 86849 

  Weighted least-squares fit:  Y = 10.5 + 0.217 X  + 0.00368 X**2 

curvature versus dZ, slope < 10
  n = 9459 
  X=0, Y = 11.28 +/- 6.54 
  Weighted least-squares fit:  Y = 10.4 + 1.365 X  + 0.07023 X**2 


Number of samples 388725
Max dz = 900
Mean dz = 64
RMS dz = 95.9009906101
100cm = 77.8223679979 percentile value of dz