curvature versus slope
  n = 533538 
  X=0, Y = 42.43 +/- 23.50 
  Weighted least-squares fit:  Y = 62.1 + 1.744 X  + -0.01885 X**2 

slope versus dZ, curvature < 5
  n = 53471 

  Weighted least-squares fit:  Y = 67.6 + -0.205 X  + 0.00460 X**2 
     at X = 100, Y = 93.1 
     effective RMSE xy = 100.5 

slope versus dZ, curvature < 15
  n = 135382 

  Weighted least-squares fit:  Y = 67.4 + -0.097 X  + 0.00410 X**2 

curvature versus dZ, slope < 10
  n = 3910 
  X=0, Y = 65.61 +/- 14.51 
  Weighted least-squares fit:  Y = 63.6 + 1.789 X  + -0.11794 X**2 


Number of samples 539257
Max dz = 900
Mean dz = 93
RMS dz = 122.53162857
100cm = 65.8626591773 percentile value of dz