curvature versus slope
  n = 103490052 
  X=0, Y = 26.70 +/- 22.79 
  Weighted least-squares fit:  Y = 31.3 + 1.294 X  + -0.00863 X**2 

slope versus dZ, curvature < 5
  n = 1840130 
  X=0, Y = 3.75 +/- 2.51 
  Weighted least-squares fit:  Y = 3.9 + 0.092 X  + 0.00174 X**2 
     at X = 100, Y = 30.5 
     effective RMSE xy = 47.5 

slope versus dZ, curvature < 15
  n = 8421531 
  X=0, Y = 3.69 +/- 2.43 
  Weighted least-squares fit:  Y = 4.0 + 0.108 X  + 0.00160 X**2 

curvature versus dZ, slope < 10
  n = 15941201 
  X=0, Y = 4.57 +/- 3.01 
  Weighted least-squares fit:  Y = 4.5 + 0.116 X  + 0.00179 X**2 


Number of samples 105736573
Max dz = 900
Mean dz = 479
RMS dz = 3204.56720947
100cm = 99.807310759 percentile value of dz
Mean dz (curv<=5) = 68
RMS dz (curv<=5) = 1259.6479667