curvature versus slope
  n = 234882 
  X=0, Y = 64.66 +/- 33.23 
  Weighted least-squares fit:  Y = 78.4 + 0.801 X  + -0.00806 X**2 

slope versus dZ, curvature < 5
  n = 7528 

  Weighted least-squares fit:  Y = 14.6 + 0.773 X  + -0.00072 X**2 
     at X = 100, Y = 84.6 
     effective RMSE xy = 131.0 

slope versus dZ, curvature < 15
  n = 27072 

  Weighted least-squares fit:  Y = 18.4 + 0.680 X  + -0.00004 X**2 

curvature versus dZ, slope < 10
  n = 350 
  X=0, Y = 23.36 +/- 11.87 
  Weighted least-squares fit:  Y = 24.0 + 0.449 X  + 0.02594 X**2 


Number of samples 238570
Max dz = 900
Mean dz = 89
RMS dz = 123.474693764
100cm = 67.8966341116 percentile value of dz