curvature versus slope
  n = 126670 
  X=0, Y = 40.00 +/- 24.92 
  Weighted least-squares fit:  Y = 56.6 + 2.075 X  + -0.02274 X**2 

slope versus dZ, curvature < 5
  n = 34300 

  Weighted least-squares fit:  Y = 67.2 + 0.115 X  + -0.00091 X**2 
     at X = 100, Y = 69.6 
     effective RMSE xy = 28.2 

slope versus dZ, curvature < 15
  n = 58694 

  Weighted least-squares fit:  Y = 67.8 + -0.002 X  + 0.00099 X**2 

curvature versus dZ, slope < 10
  n = 5745 
  X=0, Y = 59.54 +/- 37.11 
  Weighted least-squares fit:  Y = 60.4 + 0.189 X  + -0.28547 X**2 


Number of samples 128458
Max dz = 900
Mean dz = 80
RMS dz = 125.610509114
100cm = 73.5968176369 percentile value of dz