curvature versus slope
  n = 260211 
  X=0, Y = 51.86 +/- 28.78 
  Weighted least-squares fit:  Y = 67.8 + 1.279 X  + -0.01315 X**2 

slope versus dZ, curvature < 5
  n = 17616 

  Weighted least-squares fit:  Y = 42.8 + -0.055 X  + 0.00340 X**2 
     at X = 100, Y = 71.3 
     effective RMSE xy = 89.6 

slope versus dZ, curvature < 15
  n = 53469 

  Weighted least-squares fit:  Y = 43.3 + -0.115 X  + 0.00429 X**2 

curvature versus dZ, slope < 10
  n = 1402 
  X=0, Y = 42.56 +/- 9.87 
  Weighted least-squares fit:  Y = 41.1 + -0.279 X  + 0.13066 X**2 


Number of samples 264290
Max dz = 900
Mean dz = 75
RMS dz = 119.540788018
100cm = 74.7141397707 percentile value of dz