curvature versus slope
  n = 184840 
  X=0, Y = 47.30 +/- 23.07 
  Weighted least-squares fit:  Y = 55.8 + 1.628 X  + -0.01588 X**2 

slope versus dZ, curvature < 5
  n = 19872 

  Weighted least-squares fit:  Y = 39.2 + 0.774 X  + -0.00031 X**2 
     at X = 100, Y = 113.5 
     effective RMSE xy = 167.3 

slope versus dZ, curvature < 15
  n = 60689 

  Weighted least-squares fit:  Y = 40.3 + 0.763 X  + -0.00008 X**2 

curvature versus dZ, slope < 10
  n = 1129 
  X=0, Y = 47.36 +/- 10.99 
  Weighted least-squares fit:  Y = 47.5 + -0.287 X  + 0.04447 X**2 


Number of samples 185834
Max dz = 900
Mean dz = 87
RMS dz = 109.201648339
100cm = 70.3116760119 percentile value of dz