  We describe a straightforward, automated line tracking method to visualize
within optical resolution the contour of linear macromolecules as they
rearrange shape as a function of time by Brownian diffusion and under external
fields such as electrophoresis. Three sequential stages of analysis underpin
this method: first, "feature finding" to discriminate signal from noise;
second, "line tracking" to approximate those shapes as lines; third, "temporal
consistency check" to discriminate reasonable from unreasonable fitted
conformations in the time domain. The automated nature of this data analysis
makes it straightforward to accumulate vast quantities of data while excluding
the unreliable parts of it. We implement the analysis on fluorescence images of
lambda-DNA molecules in agarose gel to demonstrate its capability to produce
large datasets for subsequent statistical analysis.
