Overlay Vector Data Directly on Google Maps

It’s amazing what a few months of development can bring about in the world of web applications. When I thought that you could only directly overlay vector data on Google Earth, it seems you can now do this likewise on Google Maps. And you don’t even need third-party software or javascript to do this. As long as you have a .KML file available online, you can instruct Google Maps to overlay data or even image overlays.

First, let’s learn about what .KML files are. These are basically XML (extensible markup language) files that defines geographic information (coordinates, GPS readings), and attaches vector data, so you can include various information like waypoints, paths/streets, text, and even images or links to images.

• Placemarks - These are simply points on the globe that you define to mark points of interest that are defined by geographic coordinates.
• Descriptive text - These are text or HTML that you can use to describe the points you define with placemarks.
• Ground overlays - These are used to overlay aerial images on Google maps. This is useful if you want to compare the satellite imagery that Google maps uses with newer images. Or, you can add more detailed shots if Google maps only has low-resolution satellite imagery for certain locations.
• Paths - Using the paths feature is like tracing a route through the landscape on Google maps. You can use this to illustrate a journey, show directions, or trace roads, in case your city doesn’t have vector data for streets yet.
• Polygons - These features are like paths, but are used to trace shapes on the landscape. This is useful for identifying buildings and other establishments.

Now, once you already have .KML files you want to use with Google maps, it’s very easy to overlay data. Simply input the URL of the .KML file on the Google maps search bar (including the http://) and Google will load it for you. It’s that simple.

For instance, you can use the Discovery Channel’s National Park Tour data on Google Maps. Simply key in http://dsc.discovery.com/utilities/googleearth/nationalparks/nationalparks.kml and you can take a virtual tour right on your Web browser. Here’s the direct link.