curvature versus slope
  n = 482213 
  X=0, Y = 35.11 +/- 17.50 
  Weighted least-squares fit:  Y = 52.3 + 2.097 X  + -0.02277 X**2 

slope versus dZ, curvature < 5
  n = 127016 

  Weighted least-squares fit:  Y = 21.7 + -0.277 X  + 0.00425 X**2 
     at X = 100, Y = 36.5 
     effective RMSE xy = 46.1 

slope versus dZ, curvature < 15
  n = 221027 

  Weighted least-squares fit:  Y = 22.1 + -0.263 X  + 0.00426 X**2 

curvature versus dZ, slope < 10
  n = 8099 
  X=0, Y = 18.51 +/- 14.32 
  Weighted least-squares fit:  Y = 18.9 + 1.776 X  + -0.01456 X**2 


Number of samples 490949
Max dz = 900
Mean dz = 33
RMS dz = 59.3885510852
100cm = 93.1489828882 percentile value of dz