curvature versus slope
  n = 1508277 
  X=0, Y = 19.87 +/- 14.29 
  Weighted least-squares fit:  Y = 68.8 + 1.514 X  + -0.01426 X**2 

slope versus dZ, curvature < 5
  n = 6065 

  Weighted least-squares fit:  Y = 6.9 + -0.083 X  + 0.00186 X**2 
     at X = 100, Y = 17.2 
     effective RMSE xy = 24.7 

slope versus dZ, curvature < 15
  n = 11420 

  Weighted least-squares fit:  Y = 7.2 + -0.027 X  + 0.00205 X**2 

curvature versus dZ, slope < 10
  n = 1811 
  X=0, Y = 5.55 +/- 3.13 
  Weighted least-squares fit:  Y = 5.4 + 0.939 X  + -0.16500 X**2 


Number of samples 1519500
Max dz = 900
Mean dz = 53
RMS dz = 73.4506637138
100cm = 85.0764725239 percentile value of dz