curvature versus slope
  n = 840666 
  X=0, Y = 42.62 +/- 22.72 
  Weighted least-squares fit:  Y = 59.2 + 1.649 X  + -0.01803 X**2 

slope versus dZ, curvature < 5
  n = 40926 

  Weighted least-squares fit:  Y = 10.4 + 0.812 X  + -0.00175 X**2 
     at X = 100, Y = 74.1 
     effective RMSE xy = 115.2 

slope versus dZ, curvature < 15
  n = 129399 

  Weighted least-squares fit:  Y = 12.0 + 0.776 X  + -0.00144 X**2 

curvature versus dZ, slope < 10
  n = 3733 
  X=0, Y = 12.69 +/- 8.18 
  Weighted least-squares fit:  Y = 11.4 + 4.002 X  + -0.08795 X**2 


Number of samples 860654
Max dz = 900
Mean dz = 69
RMS dz = 96.3327566303
100cm = 76.3092950245 percentile value of dz