Contribution from all sources listed in the uncertainty budget with the constant and length dependent components shown in different solid colors. The combined value from the constant and length dependent components produce a curve. 

Result of using a best fit line to describe the curved shaped of the uncertainty data. The biggest concern with this is that the line at length zero (y intercept) is almost always lower than what could potentially be achievable by the laboratory. In some cases this value may be negative if the curve is pronounced enough. 

Comparison of actual uncertainty data calculated at different lengths as compared to the best fit curve uncertainty expression. Although the fit is not perfect it is much better at describing the real shape then what would be possible using only a line. The expression used to generate the shape is displayed below the graph with L representing the position in meters. 