curvature versus slope
  n = 316408 
  X=0, Y = 37.53 +/- 30.20 
  Weighted least-squares fit:  Y = 68.6 + 1.272 X  + -0.01344 X**2 

slope versus dZ, curvature < 5
  n = 13895 

  Weighted least-squares fit:  Y = 38.6 + 0.612 X  + -0.00119 X**2 
     at X = 100, Y = 87.9 
     effective RMSE xy = 124.0 

slope versus dZ, curvature < 15
  n = 39908 

  Weighted least-squares fit:  Y = 38.8 + 0.578 X  + -0.00063 X**2 

curvature versus dZ, slope < 10
  n = 5358 
  X=0, Y = 45.80 +/- 21.43 
  Weighted least-squares fit:  Y = 42.0 + 1.316 X  + 0.04743 X**2 


Number of samples 318665
Max dz = 900
Mean dz = 82
RMS dz = 115.243221059
100cm = 69.6734815559 percentile value of dz