curvature versus slope
  n = 472626 
  X=0, Y = 47.20 +/- 20.77 
  Weighted least-squares fit:  Y = 60.0 + 2.153 X  + -0.02486 X**2 

slope versus dZ, curvature < 5
  n = 224512 

  Weighted least-squares fit:  Y = 15.7 + -0.107 X  + 0.00467 X**2 
     at X = 100, Y = 51.7 
     effective RMSE xy = 77.4 

slope versus dZ, curvature < 15
  n = 354800 

  Weighted least-squares fit:  Y = 15.3 + -0.047 X  + 0.00442 X**2 

curvature versus dZ, slope < 10
  n = 4259 
  X=0, Y = 17.22 +/- 9.80 
  Weighted least-squares fit:  Y = 17.3 + -1.334 X  + 0.59448 X**2 


Number of samples 480569
Max dz = 900
Mean dz = 31
RMS dz = 53.2165387826
100cm = 95.7656444756 percentile value of dz