I have a page with two tabs. The first tab has photos and the second a google map. The problem is that the google map is not completely drawing because it is in a hidden div
By following the link provided from Pete, I was able to resolve that.
You probably have a function called calcRoute(). You might need to trigger this function twice. At first, when it's triggered it loads fine, but you might need to trigger that function again as well when you change the tab. That should work!