curvature versus slope
  n = 863728 
  X=0, Y = 27.93 +/- 21.75 
  Weighted least-squares fit:  Y = 66.8 + 1.540 X  + -0.01524 X**2 

slope versus dZ, curvature < 5
  n = 9525 

  Weighted least-squares fit:  Y = 17.5 + -0.004 X  + 0.00259 X**2 
     at X = 100, Y = 43.0 
     effective RMSE xy = 61.7 

slope versus dZ, curvature < 15
  n = 39761 

  Weighted least-squares fit:  Y = 15.6 + 0.310 X  + 0.00068 X**2 

curvature versus dZ, slope < 10
  n = 4194 
  X=0, Y = 20.15 +/- 12.75 
  Weighted least-squares fit:  Y = 19.1 + -0.248 X  + 0.12276 X**2 


Number of samples 879417
Max dz = 900
Mean dz = 62
RMS dz = 87.4871419124
100cm = 79.9188553326 percentile value of dz