Our biggest problem is finding the initial Tube data. Without this first step, we cannot create our mashup. The first logical step is to look at the official Tube site at http://www.tfl.gov.uk/tube/. Poking around, we see a lot of colorful maps of the lines, but nothing machine readable—no feeds and not even a pull-down menu with stations. It looks like the official site will be a poor choice as a source of data.
We should look at the Google Maps API to see what it can even accept. The documentation homepage is at http://www.google.com/apis/maps/documentation/. This site has many examples as well as class, methods, and properties references. Looking around, we see that a Google Map marker is represented by a class called GMarker. There are many examples on how to create a marker like so:
marker = new GMarker(point); map.addOverlay(marker);
That’s wonderful, but what is a point that is passed to the GMarker class? Looking at the documentation reference, we find that...