curvature versus slope
  n = 537313 
  X=0, Y = 40.90 +/- 26.48 
  Weighted least-squares fit:  Y = 60.3 + 1.553 X  + -0.01606 X**2 

slope versus dZ, curvature < 5
  n = 33945 

  Weighted least-squares fit:  Y = 15.1 + 0.020 X  + 0.00496 X**2 
     at X = 100, Y = 66.7 
     effective RMSE xy = 102.1 

slope versus dZ, curvature < 15
  n = 98599 

  Weighted least-squares fit:  Y = 14.6 + 0.149 X  + 0.00406 X**2 

curvature versus dZ, slope < 10
  n = 5020 
  X=0, Y = 12.11 +/- 8.44 
  Weighted least-squares fit:  Y = 10.4 + 2.824 X  + 0.05102 X**2 


Number of samples 544169
Max dz = 900
Mean dz = 65
RMS dz = 102.381638979
100cm = 78.7926177346 percentile value of dz