If I'm not mistaken you would have to make a version of the map for each frame. IIRC GIF will ignore portions of the image that have not changed from frame to frame, but all the editors I've used need the full frame to figure this out. I could be wrong though.
More importantly, I don't think it's a great idea. Most things can be conveyed without animation, and the use of animated GIF only prolongs the life of a format that needs to die its natural death.
Some alternatives to animated GIF would be one of the animated PNG formats, although, support is scarce among browsers. You could also use HTML canvas, although that suffers the same problem. More supported, but requiring more effort would be something made in Flash.