curvature versus slope
  n = 241949 
  X=0, Y = 21.55 +/- 18.24 
  Weighted least-squares fit:  Y = 48.4 + 2.357 X  + -0.02599 X**2 

slope versus dZ, curvature < 5
  n = 30862 

  Weighted least-squares fit:  Y = 12.1 + 0.270 X  + 0.00342 X**2 
     at X = 100, Y = 73.3 
     effective RMSE xy = 113.5 

slope versus dZ, curvature < 15
  n = 60216 

  Weighted least-squares fit:  Y = 11.4 + 0.419 X  + 0.00222 X**2 

curvature versus dZ, slope < 10
  n = 22847 
  X=0, Y = 14.98 +/- 8.06 
  Weighted least-squares fit:  Y = 14.4 + 0.654 X  + 0.14502 X**2 


Number of samples 247789
Max dz = 900
Mean dz = 61
RMS dz = 95.1735257306
100cm = 79.9224340064 percentile value of dz