curvature versus slope
  n = 1398870 
  X=0, Y = 32.18 +/- 22.09 
  Weighted least-squares fit:  Y = 49.4 + 2.081 X  + -0.02137 X**2 

slope versus dZ, curvature < 5
  n = 72367 

  Weighted least-squares fit:  Y = 8.9 + 1.525 X  + -0.00703 X**2 
     at X = 100, Y = 91.0 
     effective RMSE xy = 142.3 

slope versus dZ, curvature < 15
  n = 256075 

  Weighted least-squares fit:  Y = 12.3 + 1.544 X  + -0.00743 X**2 

curvature versus dZ, slope < 10
  n = 22406 
  X=0, Y = 23.02 +/- 15.86 
  Weighted least-squares fit:  Y = 16.2 + 6.022 X  + -0.18532 X**2 


Number of samples 1422336
Max dz = 900
Mean dz = 70
RMS dz = 96.3690821789
100cm = 73.7057910367 percentile value of dz