curvature versus slope
  n = 497294 
  X=0, Y = 66.54 +/- 28.26 
  Weighted least-squares fit:  Y = 73.4 + 0.715 X  + -0.00555 X**2 

slope versus dZ, curvature < 5
  n = 36174 

  Weighted least-squares fit:  Y = 12.1 + 1.852 X  + -0.01138 X**2 
     at X = 100, Y = 83.5 
     effective RMSE xy = 129.7 

slope versus dZ, curvature < 15
  n = 115706 

  Weighted least-squares fit:  Y = 22.7 + 1.422 X  + -0.00870 X**2 

curvature versus dZ, slope < 10
  n = 2215 
  X=0, Y = 35.34 +/- 39.00 
  Weighted least-squares fit:  Y = 39.9 + 0.479 X  + 0.00123 X**2 


Number of samples 509350
Max dz = 900
Mean dz = 63
RMS dz = 115.056507856
100cm = 84.2597428095 percentile value of dz