curvature versus slope
  n = 239414 
  X=0, Y = 34.99 +/- 30.44 
  Weighted least-squares fit:  Y = 73.6 + 1.066 X  + -0.01066 X**2 

slope versus dZ, curvature < 5
  n = 6450 

  Weighted least-squares fit:  Y = 34.3 + 0.469 X  + 0.00119 X**2 
     at X = 100, Y = 93.1 
     effective RMSE xy = 136.0 

slope versus dZ, curvature < 15
  n = 19501 

  Weighted least-squares fit:  Y = 35.3 + 0.601 X  + -0.00016 X**2 

curvature versus dZ, slope < 10
  n = 3237 
  X=0, Y = 38.44 +/- 15.66 
  Weighted least-squares fit:  Y = 39.2 + -0.132 X  + 0.14785 X**2 


Number of samples 240756
Max dz = 900
Mean dz = 94
RMS dz = 134.082064423
100cm = 64.2077456014 percentile value of dz