Tabular data, in the form of spreadsheets, is familiar to us; the geographic data, in the form of KML files, is new to many people. Among others, two common questions Fusion Tables map beginners have are (a) What is KML file? and (b) where to find the KML file for my project at hand?
(This post is part four of a 5-part tutorial on creating Fusion Tables intensity map; the other parts are listed as related posts at end of this post)
What is KML/KMZ and how to open it?
KML stands for Keyhole Markup Language, which is a file format used to display geographic data in an Earth browser such as Google Earth, Google Maps, and Google Maps for mobile. KML files are usually distributed (e.g., via email) in KMZ files, which stands for Keyhole Markup language Zippped and is a compressed version of KML file. A typical KML/KMZ file contains geographical data like latitude, longitude, points, lines and text to illustrate the location.
A KML file comes with .kml extension and KMZ files come with .kmz extension. Just like a .doc file can be opened by a software program (e.g., Word, TextEdit) that edits texts, a .kml or .kmz file can be opened by programs that process geographic data – Google Earth and Google Maps, among others, are two popular programs that both create and read KML/KMZ files.
Where to find KML files I need for a project?
We usually can find ready-made KML files for common mapping needs. Below is a collection of resources that I have found useful. I encourage readers of this post to suggest additional resources by leaving a comment to this post, tweeting me @mututemple or emailing to email@example.com.
- USA: State, County and Congressional District boundaries: These tables offer boundaries obtained from the U.S. Census Bureau and imported by the Fusion Tables team. They are public and can be used freely. Note that these KML files are already uploaded and being shared, which means you can directly merge one with your table; consult part 5 of this tutorial series for how to merge data and KML.
- Many U.S. cities offer free geographic data as part of the civic and public services. For instance, New York City, Chicago, Los Angeles.
- GeoCommons: GeoCommons is the public community of GeoIQ users who are building an open repository of data and maps for the world. You can search and, if available, download a KML file.
- Fusion Tables public files: Fusion Tables users from around the world upload and share lots of tables, which include tabular data and geographic data.
Find and use public KML data
There are people from around the world who upload and share all kinds of data sets on Fusion Tables. If you need a KML file for a mapping project but could not find one, you can try searching the Fushion Tables public data. For instance, I need a KML boundary file for zip codes in Florida, so I typed the search terms as shown below (make sure you click and select Fusion Tables),
On the results page, I found one file titled “Florida Zips KML;” clicking it and I saw a table with a KML column, as shown below. Notice that if you want to preview this table on a map, you need to click on that “Switch to new look” button and on the next window, click on the red box with a white plus sign, then in the dropdown menu select “Add map,” you then will see the map view, where Fusion Tables automatically looks in the Zip Boundary column for the geographic information and plot the associated zip codes on the map.
If you have a table of Florida crime rates by zip code, you can then merge these two tables to create a heat map. Read this tutorial on how to find and use KML data for how to create heat map by merging your own table and public KML data.
Who else uses KML?
The KML community is wide and varied, as you’ll see when you visit the Google Earth community forum. Casual users create KML files to placemark their homes, to document journeys, and to plan cross-country hikes and cycling ventures. Scientists use KML to provide detailed mappings of resources, models, and trends such as volcanic eruptions, weather patterns, earthquake activity, and mineral deposits. Real estate professionals, architects, and city development agencies use KML to propose construction and visualize plans. Students and teachers use KML to explore people, places, and events, both historic and current. Organizations such as National Geographic, UNESCO, and the Smithsonian have all used KML to display their rich sets of global data.
Want to learn more about Google mapping? Here’s some popular books on Amazon that you can check out: