curvature versus slope
  n = 616193 
  X=0, Y = 53.69 +/- 16.30 
  Weighted least-squares fit:  Y = 63.6 + 1.795 X  + -0.02007 X**2 

slope versus dZ, curvature < 5
  n = 238429 

  Weighted least-squares fit:  Y = 15.5 + 0.989 X  + -0.00186 X**2 
     at X = 100, Y = 95.8 
     effective RMSE xy = 148.5 

slope versus dZ, curvature < 15
  n = 394226 

  Weighted least-squares fit:  Y = 15.2 + 1.054 X  + -0.00223 X**2 

curvature versus dZ, slope < 10
  n = 39 
  X=0, Y = 28.68 +/- 4.46 
  Weighted least-squares fit:  Y = 25.7 + 6.203 X  + -0.37803 X**2 


Number of samples 628833
Max dz = 900
Mean dz = 76
RMS dz = 96.322375386
100cm = 79.1081256868 percentile value of dz