curvature versus slope
  n = 265198 
  X=0, Y = 22.43 +/- 19.33 
  Weighted least-squares fit:  Y = 50.3 + 2.139 X  + -0.02243 X**2 

slope versus dZ, curvature < 5
  n = 21385 

  Weighted least-squares fit:  Y = 7.2 + 0.327 X  + 0.00327 X**2 
     at X = 100, Y = 72.6 
     effective RMSE xy = 113.5 

slope versus dZ, curvature < 15
  n = 48808 

  Weighted least-squares fit:  Y = 7.1 + 0.445 X  + 0.00230 X**2 

curvature versus dZ, slope < 10
  n = 15629 
  X=0, Y = 9.11 +/- 6.10 
  Weighted least-squares fit:  Y = 9.2 + 1.097 X  + 0.04566 X**2 


Number of samples 267773
Max dz = 900
Mean dz = 65
RMS dz = 100.41414243
100cm = 77.6239576059 percentile value of dz