curvature versus slope
  n = 506926 
  X=0, Y = 50.52 +/- 32.64 
  Weighted least-squares fit:  Y = 73.3 + 1.339 X  + -0.01360 X**2 

slope versus dZ, curvature < 5
  n = 17317 

  Weighted least-squares fit:  Y = 40.4 + 0.507 X  + 0.00056 X**2 
     at X = 100, Y = 96.8 
     effective RMSE xy = 138.1 

slope versus dZ, curvature < 15
  n = 98380 

  Weighted least-squares fit:  Y = 41.3 + 0.689 X  + -0.00097 X**2 

curvature versus dZ, slope < 10
  n = 3052 
  X=0, Y = 55.67 +/- 31.43 
  Weighted least-squares fit:  Y = 56.0 + -0.063 X  + -0.03794 X**2 


Number of samples 510297
Max dz = 900
Mean dz = 86
RMS dz = 113.494493258
100cm = 66.9780539568 percentile value of dz