curvature versus slope
  n = 1391362 
  X=0, Y = 39.53 +/- 21.22 
  Weighted least-squares fit:  Y = 36.8 + 0.981 X  + -0.00496 X**2 

slope versus dZ, curvature < 5
  n = 15738 

  Weighted least-squares fit:  Y = 4.0 + 0.081 X  + 0.00112 X**2 
     at X = 100, Y = 23.3 
     effective RMSE xy = 36.1 

slope versus dZ, curvature < 15
  n = 75006 

  Weighted least-squares fit:  Y = 4.3 + 0.060 X  + 0.00146 X**2 

curvature versus dZ, slope < 10
  n = 47280 
  X=0, Y = 4.73 +/- 2.68 
  Weighted least-squares fit:  Y = 3.9 + 0.191 X  + -0.00062 X**2 


Number of samples 1393971
Max dz = 900
Mean dz = 12
RMS dz = 21.0237960416
100cm = 99.7784028506 percentile value of dz
Mean dz (curv<=5) = 7
RMS dz (curv<=5) = 10.3923048454