curvature versus slope
  n = 89200 
  X=0, Y = 44.69 +/- 26.82 
  Weighted least-squares fit:  Y = 64.3 + 1.624 X  + -0.01773 X**2 

slope versus dZ, curvature < 5
  n = 22056 

  Weighted least-squares fit:  Y = 33.7 + -0.448 X  + 0.00766 X**2 
     at X = 100, Y = 65.5 
     effective RMSE xy = 88.3 

slope versus dZ, curvature < 15
  n = 39140 

  Weighted least-squares fit:  Y = 33.7 + -0.411 X  + 0.00770 X**2 

curvature versus dZ, slope < 10
  n = 3790 
  X=0, Y = 33.12 +/- 18.56 
  Weighted least-squares fit:  Y = 32.4 + 1.954 X  + -0.36681 X**2 


Number of samples 90936
Max dz = 900
Mean dz = 70
RMS dz = 123.490890352
100cm = 80.0387085423 percentile value of dz