curvature versus slope
  n = 2949094 
  X=0, Y = 23.32 +/- 20.55 
  Weighted least-squares fit:  Y = 36.9 + 3.433 X  + -0.03831 X**2 

slope versus dZ, curvature < 5
  n = 286210 

  Weighted least-squares fit:  Y = 17.7 + 0.125 X  + 0.00145 X**2 
     at X = 100, Y = 44.7 
     effective RMSE xy = 64.4 

slope versus dZ, curvature < 15
  n = 736114 

  Weighted least-squares fit:  Y = 16.9 + 0.262 X  + 0.00092 X**2 

curvature versus dZ, slope < 10
  n = 274785 
  X=0, Y = 18.23 +/- 11.40 
  Weighted least-squares fit:  Y = 17.6 + 1.539 X  + -0.06694 X**2 


Number of samples 2999269
Max dz = 800
Mean dz = 45
RMS dz = 65.9090282131
100cm = 88.2005915441 percentile value of dz