curvature versus slope
  n = 864941 
  X=0, Y = 17.09 +/- 14.00 
  Weighted least-squares fit:  Y = 46.1 + 2.849 X  + -0.03236 X**2 

slope versus dZ, curvature < 5
  n = 151853 

  Weighted least-squares fit:  Y = 35.3 + 0.056 X  + 0.00324 X**2 
     at X = 100, Y = 73.3 
     effective RMSE xy = 100.9 

slope versus dZ, curvature < 15
  n = 261284 

  Weighted least-squares fit:  Y = 33.9 + 0.234 X  + 0.00217 X**2 

curvature versus dZ, slope < 10
  n = 110006 
  X=0, Y = 36.13 +/- 20.24 
  Weighted least-squares fit:  Y = 36.3 + -0.350 X  + 0.08361 X**2 


Number of samples 884219
Max dz = 900
Mean dz = 65
RMS dz = 95.7810002036
100cm = 79.601772864 percentile value of dz