curvature versus slope
  n = 187488 
  X=0, Y = 42.67 +/- 23.64 
  Weighted least-squares fit:  Y = 55.3 + 1.671 X  + -0.01701 X**2 

slope versus dZ, curvature < 5
  n = 24948 

  Weighted least-squares fit:  Y = 50.4 + 0.701 X  + 0.00027 X**2 
     at X = 100, Y = 123.2 
     effective RMSE xy = 176.6 

slope versus dZ, curvature < 15
  n = 68512 

  Weighted least-squares fit:  Y = 50.1 + 0.763 X  + -0.00041 X**2 

curvature versus dZ, slope < 10
  n = 1151 
  X=0, Y = 59.65 +/- 9.50 
  Weighted least-squares fit:  Y = 58.0 + 1.441 X  + -0.02953 X**2 


Number of samples 188482
Max dz = 900
Mean dz = 92
RMS dz = 116.948706705
100cm = 65.0666907185 percentile value of dz