curvature versus slope
  n = 418703 
  X=0, Y = 43.79 +/- 31.56 
  Weighted least-squares fit:  Y = 75.8 + 1.056 X  + -0.01102 X**2 

slope versus dZ, curvature < 5
  n = 6197 

  Weighted least-squares fit:  Y = 8.1 + 0.092 X  + 0.00586 X**2 
     at X = 100, Y = 75.9 
     effective RMSE xy = 118.6 

slope versus dZ, curvature < 15
  n = 23075 

  Weighted least-squares fit:  Y = 5.2 + 0.473 X  + 0.00266 X**2 

curvature versus dZ, slope < 10
  n = 1351 
  X=0, Y = 8.64 +/- 6.16 
  Weighted least-squares fit:  Y = 7.9 + 2.611 X  + -0.05186 X**2 


Number of samples 426657
Max dz = 900
Mean dz = 88
RMS dz = 125.582642113
100cm = 66.7819817793 percentile value of dz