Plot And Attach Pixels To A Scrolling Image

I have an img of a map of Europe in a div. I want to plot routes between cities in Europe as dotted lines. The image is scrollable and I want the routes to scroll with the image. So the routes should be attached to the image. Furthermore, when drawing routes outside of the viewable area, the routes should be clipped so they don't show up outside of the image. but when the image is scrolled, the routes should appear.

Here's a link to the dev site: [url]

Here is my code:

CSS:

HTML

FBJS (Facebook JS)