curvature versus slope
  n = 624235 
  X=0, Y = 41.28 +/- 24.71 
  Weighted least-squares fit:  Y = 55.0 + 2.135 X  + -0.02316 X**2 

slope versus dZ, curvature < 5
  n = 54878 

  Weighted least-squares fit:  Y = 125.2 + 0.784 X  + -0.00735 X**2 
     at X = 100, Y = 130.1 
     effective RMSE xy = 55.3 

slope versus dZ, curvature < 15
  n = 161764 

  Weighted least-squares fit:  Y = 128.8 + 0.581 X  + -0.00503 X**2 

curvature versus dZ, slope < 10
  n = 9375 
  X=0, Y = 121.70 +/- 48.69 
  Weighted least-squares fit:  Y = 131.9 + -0.723 X  + -0.20139 X**2 


Number of samples 626979
Max dz = 900
Mean dz = 126
RMS dz = 153.489413316
100cm = 41.2187649028 percentile value of dz