curvature versus slope
  n = 402222 
  X=0, Y = 36.12 +/- 18.01 
  Weighted least-squares fit:  Y = 53.3 + 1.997 X  + -0.02169 X**2 

slope versus dZ, curvature < 5
  n = 84999 

  Weighted least-squares fit:  Y = 46.2 + -0.640 X  + 0.00975 X**2 
     at X = 100, Y = 79.7 
     effective RMSE xy = 102.1 

slope versus dZ, curvature < 15
  n = 149197 

  Weighted least-squares fit:  Y = 44.2 + -0.302 X  + 0.00671 X**2 

curvature versus dZ, slope < 10
  n = 4139 
  X=0, Y = 61.73 +/- 36.08 
  Weighted least-squares fit:  Y = 66.4 + -5.153 X  + 0.25142 X**2 


Number of samples 414167
Max dz = 900
Mean dz = 64
RMS dz = 96.3898334888
100cm = 77.5076237363 percentile value of dz