curvature versus slope
  n = 447148 
  X=0, Y = 28.96 +/- 24.65 
  Weighted least-squares fit:  Y = 54.1 + 2.282 X  + -0.02509 X**2 

slope versus dZ, curvature < 5
  n = 53001 

  Weighted least-squares fit:  Y = 30.8 + -0.011 X  + 0.00317 X**2 
     at X = 100, Y = 61.4 
     effective RMSE xy = 83.4 

slope versus dZ, curvature < 15
  n = 113211 

  Weighted least-squares fit:  Y = 29.7 + 0.137 X  + 0.00244 X**2 

curvature versus dZ, slope < 10
  n = 35369 
  X=0, Y = 30.19 +/- 15.53 
  Weighted least-squares fit:  Y = 29.7 + 0.593 X  + -0.00265 X**2 


Number of samples 461011
Max dz = 900
Mean dz = 68
RMS dz = 98.8483687271
100cm = 77.8185336142 percentile value of dz