curvature versus slope
  n = 131806 
  X=0, Y = 32.43 +/- 26.04 
  Weighted least-squares fit:  Y = 66.0 + 1.372 X  + -0.01485 X**2 

slope versus dZ, curvature < 5
  n = 7006 

  Weighted least-squares fit:  Y = 12.4 + 0.464 X  + 0.00163 X**2 
     at X = 100, Y = 75.1 
     effective RMSE xy = 116.3 

slope versus dZ, curvature < 15
  n = 16839 

  Weighted least-squares fit:  Y = 13.0 + 0.467 X  + 0.00186 X**2 

curvature versus dZ, slope < 10
  n = 2838 
  X=0, Y = 16.95 +/- 9.47 
  Weighted least-squares fit:  Y = 16.0 + 2.216 X  + -0.02484 X**2 


Number of samples 133363
Max dz = 900
Mean dz = 77
RMS dz = 131.365901207
100cm = 73.0479968207 percentile value of dz