curvature versus slope
  n = 3402399 
  X=0, Y = 25.92 +/- 18.34 
  Weighted least-squares fit:  Y = 50.5 + 2.270 X  + -0.02337 X**2 

slope versus dZ, curvature < 5
  n = 78285 

  Weighted least-squares fit:  Y = 13.0 + 0.062 X  + 0.00113 X**2 
     at X = 100, Y = 30.5 
     effective RMSE xy = 43.4 

slope versus dZ, curvature < 15
  n = 496100 

  Weighted least-squares fit:  Y = 13.5 + 0.117 X  + 0.00097 X**2 

curvature versus dZ, slope < 10
  n = 26320 
  X=0, Y = 12.83 +/- 8.56 
  Weighted least-squares fit:  Y = 13.7 + 0.253 X  + 0.07615 X**2 


Number of samples 3466127
Max dz = 900
Mean dz = 35
RMS dz = 52.5642464038
100cm = 93.468213946 percentile value of dz