curvature versus slope
  n = 541508 
  X=0, Y = 57.00 +/- 31.73 
  Weighted least-squares fit:  Y = 65.1 + 1.483 X  + -0.01440 X**2 

slope versus dZ, curvature < 5
  n = 5143 

  Weighted least-squares fit:  Y = 10.9 + 0.223 X  + 0.00002 X**2 
     at X = 100, Y = 33.4 
     effective RMSE xy = 49.5 

slope versus dZ, curvature < 15
  n = 33983 

  Weighted least-squares fit:  Y = 10.1 + 0.435 X  + -0.00132 X**2 

curvature versus dZ, slope < 10
  n = 1008 
  X=0, Y = 12.04 +/- 6.51 
  Weighted least-squares fit:  Y = 14.7 + -1.902 X  + 0.14956 X**2 


Number of samples 546892
Max dz = 900
Mean dz = 51
RMS dz = 74.2361098119
100cm = 86.3064371028 percentile value of dz