curvature versus slope
  n = 859171 
  X=0, Y = 17.15 +/- 12.63 
  Weighted least-squares fit:  Y = 30.2 + 3.622 X  + -0.04106 X**2 

slope versus dZ, curvature < 5
  n = 216389 

  Weighted least-squares fit:  Y = 13.4 + 0.400 X  + 0.00108 X**2 
     at X = 100, Y = 64.2 
     effective RMSE xy = 98.6 

slope versus dZ, curvature < 15
  n = 397780 

  Weighted least-squares fit:  Y = 13.2 + 0.479 X  + 0.00098 X**2 

curvature versus dZ, slope < 10
  n = 196392 
  X=0, Y = 14.60 +/- 8.35 
  Weighted least-squares fit:  Y = 15.2 + 0.746 X  + 0.11401 X**2 


Number of samples 872259
Max dz = 900
Mean dz = 43
RMS dz = 73.6274405368
100cm = 88.3509370497 percentile value of dz