curvature versus slope
  n = 607517 
  X=0, Y = 24.25 +/- 17.48 
  Weighted least-squares fit:  Y = 50.5 + 2.371 X  + -0.02583 X**2 

slope versus dZ, curvature < 5
  n = 51223 

  Weighted least-squares fit:  Y = 34.5 + 0.158 X  + 0.00230 X**2 
     at X = 100, Y = 73.3 
     effective RMSE xy = 101.5 

slope versus dZ, curvature < 15
  n = 118755 

  Weighted least-squares fit:  Y = 33.2 + 0.346 X  + 0.00113 X**2 

curvature versus dZ, slope < 10
  n = 23336 
  X=0, Y = 36.40 +/- 13.54 
  Weighted least-squares fit:  Y = 36.2 + 1.082 X  + -0.06460 X**2 


Number of samples 612410
Max dz = 900
Mean dz = 75
RMS dz = 105.0428484
100cm = 74.0257343936 percentile value of dz