curvature versus slope
  n = 308471 
  X=0, Y = 41.63 +/- 33.12 
  Weighted least-squares fit:  Y = 69.0 + 1.114 X  + -0.01114 X**2 

slope versus dZ, curvature < 5
  n = 10647 

  Weighted least-squares fit:  Y = 10.9 + 0.311 X  + 0.00003 X**2 
     at X = 100, Y = 42.3 
     effective RMSE xy = 64.2 

slope versus dZ, curvature < 15
  n = 31702 

  Weighted least-squares fit:  Y = 11.4 + 0.370 X  + -0.00033 X**2 

curvature versus dZ, slope < 10
  n = 3956 
  X=0, Y = 12.15 +/- 8.40 
  Weighted least-squares fit:  Y = 10.7 + 2.489 X  + -0.00151 X**2 


Number of samples 311989
Max dz = 800
Mean dz = 54
RMS dz = 77.5822144567
100cm = 84.1875835366 percentile value of dz