Here is an extensively mapped image database of Trajans column (http://cheiron.mcmaster.ca/~trajan/index.html). The site maps the continuous spiral layout of the column's artwork with cartoons that have annotations and links to high resolution images. The navigation allows you to move up and down the column and see either individual panels or a whole spiral piece around the column at a particular height. The image below shows the navigation mechanism.
Trajans column is much bigger than I had imagined - the human figures are about 2/3 full size and the inside of the column has a spiral staircase.