curvature versus slope
  n = 649647 
  X=0, Y = 45.49 +/- 18.37 
  Weighted least-squares fit:  Y = 53.3 + 2.533 X  + -0.02920 X**2 

slope versus dZ, curvature < 5
  n = 365391 

  Weighted least-squares fit:  Y = 13.1 + 0.254 X  + 0.00182 X**2 
     at X = 100, Y = 56.7 
     effective RMSE xy = 86.7 

slope versus dZ, curvature < 15
  n = 546572 

  Weighted least-squares fit:  Y = 12.5 + 0.331 X  + 0.00137 X**2 

curvature versus dZ, slope < 10
  n = 6452 
  X=0, Y = 16.59 +/- 8.67 
  Weighted least-squares fit:  Y = 15.7 + 2.031 X  + -0.38578 X**2 


Number of samples 654439
Max dz = 900
Mean dz = 30
RMS dz = 45.0
100cm = 98.0477936064 percentile value of dz