curvature versus slope
  n = 171927 
  X=0, Y = 50.50 +/- 20.41 
  Weighted least-squares fit:  Y = 51.1 + 0.799 X  + -0.00516 X**2 

slope versus dZ, curvature < 5
  n = 4334 

  Weighted least-squares fit:  Y = -0.5 + 0.322 X  + -0.00090 X**2 
     at X = 100, Y = 22.6 
     effective RMSE xy = 35.6 

slope versus dZ, curvature < 15
  n = 18251 

  Weighted least-squares fit:  Y = 0.6 + 0.250 X  + 0.00029 X**2 

curvature versus dZ, slope < 10
  n = 802 
  X=0, Y = 6.00 +/- 4.00 
  Weighted least-squares fit:  Y = 3.3 + 0.271 X  + -0.00307 X**2 


Number of samples 182031
Max dz = 800
Mean dz = 1473
RMS dz = 6189.68787581
100cm = 98.277765875 percentile value of dz
Mean dz (curv<=5) = 348
RMS dz (curv<=5) = 2968.57710023