curvature versus slope
  n = 461194 
  X=0, Y = 53.07 +/- 15.40 
  Weighted least-squares fit:  Y = 57.9 + 2.055 X  + -0.02305 X**2 

slope versus dZ, curvature < 5
  n = 229019 

  Weighted least-squares fit:  Y = 4.8 + 1.350 X  + -0.00525 X**2 
     at X = 100, Y = 87.4 
     effective RMSE xy = 137.1 

slope versus dZ, curvature < 15
  n = 359449 

  Weighted least-squares fit:  Y = 5.0 + 1.376 X  + -0.00515 X**2 

curvature versus dZ, slope < 10
  n = 929 
  X=0, Y = 14.11 +/- 5.83 
  Weighted least-squares fit:  Y = 14.7 + 0.460 X  + 0.25625 X**2 


Number of samples 464349
Max dz = 900
Mean dz = 65
RMS dz = 83.6301381082
100cm = 88.6402253477 percentile value of dz