curvature versus slope
  n = 1264028 
  X=0, Y = 21.41 +/- 16.50 
  Weighted least-squares fit:  Y = 41.5 + 2.706 X  + -0.02828 X**2 

slope versus dZ, curvature < 5
  n = 70528 

  Weighted least-squares fit:  Y = 8.8 + 0.059 X  + 0.00174 X**2 
     at X = 100, Y = 32.1 
     effective RMSE xy = 48.5 

slope versus dZ, curvature < 15
  n = 195726 

  Weighted least-squares fit:  Y = 8.3 + 0.182 X  + 0.00124 X**2 

curvature versus dZ, slope < 10
  n = 61498 
  X=0, Y = 8.94 +/- 5.41 
  Weighted least-squares fit:  Y = 9.1 + 0.479 X  + 0.07583 X**2 


Number of samples 1275873
Max dz = 900
Mean dz = 47
RMS dz = 71.5471872263
100cm = 86.0850570551 percentile value of dz