curvature versus slope
  n = 786586 
  X=0, Y = 33.42 +/- 27.83 
  Weighted least-squares fit:  Y = 66.5 + 1.451 X  + -0.01533 X**2 

slope versus dZ, curvature < 5
  n = 33577 

  Weighted least-squares fit:  Y = 31.9 + 0.435 X  + 0.00021 X**2 
     at X = 100, Y = 77.5 
     effective RMSE xy = 110.9 

slope versus dZ, curvature < 15
  n = 96717 

  Weighted least-squares fit:  Y = 33.7 + 0.327 X  + 0.00164 X**2 

curvature versus dZ, slope < 10
  n = 16086 
  X=0, Y = 30.89 +/- 14.58 
  Weighted least-squares fit:  Y = 31.2 + 2.990 X  + -0.12387 X**2 


Number of samples 790535
Max dz = 900
Mean dz = 74
RMS dz = 101.774260007
100cm = 73.767132385 percentile value of dz