curvature versus slope
  n = 159372 
  X=0, Y = 59.49 +/- 25.13 
  Weighted least-squares fit:  Y = 67.8 + 1.487 X  + -0.01563 X**2 

slope versus dZ, curvature < 5
  n = 85515 

  Weighted least-squares fit:  Y = 1.0 + 1.170 X  + -0.00766 X**2 
     at X = 100, Y = 41.5 
     effective RMSE xy = 65.1 

slope versus dZ, curvature < 15
  n = 129501 

  Weighted least-squares fit:  Y = 2.0 + 1.136 X  + -0.00691 X**2 

curvature versus dZ, slope < 10
  n = 2912 
  X=0, Y = 7.21 +/- 4.71 
  Weighted least-squares fit:  Y = 7.0 + 1.917 X  + 0.08380 X**2 


Number of samples 160462
Max dz = 900
Mean dz = 42
RMS dz = 83.58827669
100cm = 95.4369258765 percentile value of dz