curvature versus slope
  n = 1743044 
  X=0, Y = 34.39 +/- 25.14 
  Weighted least-squares fit:  Y = 60.2 + 1.991 X  + -0.02140 X**2 

slope versus dZ, curvature < 5
  n = 40674 

  Weighted least-squares fit:  Y = 32.1 + 0.219 X  + -0.00025 X**2 
     at X = 100, Y = 51.5 
     effective RMSE xy = 63.2 

slope versus dZ, curvature < 15
  n = 178322 

  Weighted least-squares fit:  Y = 32.4 + 0.225 X  + 0.00198 X**2 

curvature versus dZ, slope < 10
  n = 12480 
  X=0, Y = 26.23 +/- 21.46 
  Weighted least-squares fit:  Y = 30.6 + 1.231 X  + 0.05755 X**2 


Number of samples 1750570
Max dz = 900
Mean dz = 74
RMS dz = 101.533245787
100cm = 72.7771525846 percentile value of dz