curvature versus slope
  n = 611069 
  X=0, Y = 16.94 +/- 12.76 
  Weighted least-squares fit:  Y = 38.3 + 3.082 X  + -0.03495 X**2 

slope versus dZ, curvature < 5
  n = 103845 

  Weighted least-squares fit:  Y = 38.4 + 0.366 X  + 0.00045 X**2 
     at X = 100, Y = 79.5 
     effective RMSE xy = 109.4 

slope versus dZ, curvature < 15
  n = 200743 

  Weighted least-squares fit:  Y = 36.8 + 0.550 X  + -0.00083 X**2 

curvature versus dZ, slope < 10
  n = 80994 
  X=0, Y = 41.76 +/- 20.36 
  Weighted least-squares fit:  Y = 39.5 + 2.040 X  + -0.11379 X**2 


Number of samples 623229
Max dz = 900
Mean dz = 67
RMS dz = 94.1541289589
100cm = 79.1933623114 percentile value of dz