curvature versus slope
  n = 57816 
  X=0, Y = 25.23 +/- 20.30 
  Weighted least-squares fit:  Y = 63.0 + 1.671 X  + -0.01770 X**2 

slope versus dZ, curvature < 5
  n = 4535 

  Weighted least-squares fit:  Y = 50.1 + 0.045 X  + 0.00417 X**2 
     at X = 100, Y = 96.3 
     effective RMSE xy = 129.2 

slope versus dZ, curvature < 15
  n = 7767 

  Weighted least-squares fit:  Y = 48.8 + 0.292 X  + 0.00273 X**2 

curvature versus dZ, slope < 10
  n = 2185 
  X=0, Y = 48.63 +/- 16.57 
  Weighted least-squares fit:  Y = 50.9 + -0.025 X  + 0.07970 X**2 


Number of samples 58878
Max dz = 900
Mean dz = 116
RMS dz = 163.615402698
100cm = 57.3694758653 percentile value of dz