curvature versus slope
  n = 624244 
  X=0, Y = 43.87 +/- 30.60 
  Weighted least-squares fit:  Y = 75.6 + 1.068 X  + -0.01009 X**2 

slope versus dZ, curvature < 5
  n = 2674 

  Weighted least-squares fit:  Y = 14.3 + -0.231 X  + 0.00401 X**2 
     at X = 100, Y = 31.3 
     effective RMSE xy = 43.7 

slope versus dZ, curvature < 15
  n = 11941 

  Weighted least-squares fit:  Y = 10.8 + 0.283 X  + 0.00069 X**2 

curvature versus dZ, slope < 10
  n = 1506 
  X=0, Y = 10.87 +/- 6.25 
  Weighted least-squares fit:  Y = 10.8 + 2.042 X  + -0.33071 X**2 


Number of samples 639241
Max dz = 900
Mean dz = 66
RMS dz = 92.7469676054
100cm = 78.1892901112 percentile value of dz