curvature versus slope
  n = 1530987 
  X=0, Y = 9.82 +/- 6.71 
  Weighted least-squares fit:  Y = 33.4 + 3.549 X  + -0.03899 X**2 

slope versus dZ, curvature < 5
  n = 217570 

  Weighted least-squares fit:  Y = 9.6 + 0.149 X  + 0.00155 X**2 
     at X = 100, Y = 40.1 
     effective RMSE xy = 61.1 

slope versus dZ, curvature < 15
  n = 364031 

  Weighted least-squares fit:  Y = 11.4 + 0.190 X  + 0.00169 X**2 

curvature versus dZ, slope < 10
  n = 203721 
  X=0, Y = 8.06 +/- 5.85 
  Weighted least-squares fit:  Y = 8.5 + 4.603 X  + -0.21871 X**2 


Number of samples 1548341
Max dz = 900
Mean dz = 47
RMS dz = 73.3484832836
100cm = 85.7103183343 percentile value of dz