curvature versus slope
  n = 404444 
  X=0, Y = 71.13 +/- 23.35 
  Weighted least-squares fit:  Y = 76.3 + 1.065 X  + -0.01016 X**2 

slope versus dZ, curvature < 5
  n = 8428 

  Weighted least-squares fit:  Y = 11.3 + 0.289 X  + -0.00017 X**2 
     at X = 100, Y = 38.6 
     effective RMSE xy = 57.9 

slope versus dZ, curvature < 15
  n = 81385 

  Weighted least-squares fit:  Y = 15.5 + 0.225 X  + 0.00011 X**2 

curvature versus dZ, slope < 10
  n = 283 

  Weighted least-squares fit:  Y = 19.3 + 1.327 X  + -0.55112 X**2 


Number of samples 409781
Max dz = 900
Mean dz = 40
RMS dz = 63.8200595424
100cm = 92.8822956652 percentile value of dz