curvature versus slope
  n = 961119 
  X=0, Y = 38.47 +/- 21.93 
  Weighted least-squares fit:  Y = 45.2 + 2.483 X  + -0.02566 X**2 

slope versus dZ, curvature < 5
  n = 128288 

  Weighted least-squares fit:  Y = 51.8 + 0.421 X  + -0.00274 X**2 
     at X = 100, Y = 66.5 
     effective RMSE xy = 65.6 

slope versus dZ, curvature < 15
  n = 388608 

  Weighted least-squares fit:  Y = 51.5 + 0.413 X  + -0.00200 X**2 

curvature versus dZ, slope < 10
  n = 16848 
  X=0, Y = 56.81 +/- 19.92 
  Weighted least-squares fit:  Y = 56.7 + -0.097 X  + 0.02639 X**2 


Number of samples 973603
Max dz = 900
Mean dz = 69
RMS dz = 87.0287308881
100cm = 82.0928037403 percentile value of dz