curvature versus slope
  n = 652828 
  X=0, Y = 20.46 +/- 17.77 
  Weighted least-squares fit:  Y = 46.7 + 2.609 X  + -0.02961 X**2 

slope versus dZ, curvature < 5
  n = 107363 
  X=0, Y = 12.30 +/- 7.64 
  Weighted least-squares fit:  Y = 17.1 + 0.331 X  + 0.00198 X**2 
     at X = 100, Y = 70.1 
     effective RMSE xy = 106.7 

slope versus dZ, curvature < 15
  n = 212385 
  X=0, Y = 16.61 +/- 10.84 
  Weighted least-squares fit:  Y = 17.5 + 0.391 X  + 0.00138 X**2 

curvature versus dZ, slope < 10
  n = 79569 
  X=0, Y = 17.70 +/- 11.45 
  Weighted least-squares fit:  Y = 18.4 + 2.428 X  + -0.01305 X**2 


Number of samples 660893
Max dz = 900
Mean dz = 53
RMS dz = 80.7403244977
100cm = 84.4841751993 percentile value of dz