curvature versus slope
  n = 305864 
  X=0, Y = 38.79 +/- 26.57 
  Weighted least-squares fit:  Y = 58.2 + 1.813 X  + -0.01879 X**2 

slope versus dZ, curvature < 5
  n = 35230 

  Weighted least-squares fit:  Y = 25.1 + -0.158 X  + 0.00435 X**2 
     at X = 100, Y = 52.8 
     effective RMSE xy = 73.0 

slope versus dZ, curvature < 15
  n = 92171 

  Weighted least-squares fit:  Y = 26.7 + -0.106 X  + 0.00389 X**2 

curvature versus dZ, slope < 10
  n = 5709 
  X=0, Y = 17.34 +/- 9.50 
  Weighted least-squares fit:  Y = 18.8 + 5.807 X  + -0.30651 X**2 


Number of samples 309301
Max dz = 900
Mean dz = 48
RMS dz = 83.0240928888
100cm = 88.4025593192 percentile value of dz
Mean dz (curv<=5) = 23
RMS dz (curv<=5) = 48.6209831246