curvature versus slope
  n = 2604393 
  X=0, Y = 40.23 +/- 23.57 
  Weighted least-squares fit:  Y = 50.2 + 2.266 X  + -0.02332 X**2 

slope versus dZ, curvature < 5
  n = 81588 

  Weighted least-squares fit:  Y = 23.1 + -0.142 X  + 0.00187 X**2 
     at X = 100, Y = 27.6 
     effective RMSE xy = 23.7 

slope versus dZ, curvature < 15
  n = 492539 

  Weighted least-squares fit:  Y = 26.3 + -0.235 X  + 0.00383 X**2 

curvature versus dZ, slope < 10
  n = 6355 
  X=0, Y = 24.37 +/- 19.39 
  Weighted least-squares fit:  Y = 26.0 + 0.624 X  + 0.05853 X**2 


Number of samples 2640996
Max dz = 800
Mean dz = 39
RMS dz = 58.0258563056
100cm = 91.6054019014 percentile value of dz