The United States Geological Survey’s website provides map downloads of geologic unit data. You can download and view these files in Google Earth. This makes Google Earth a “killer app” for geologists, paleontologists, and other earth sciences explorers. What an amazing resource for understanding and exploring the surface rocks of a given area!
My partner Heidi and I love to camp and explore areas in which the terrain may have fossil bearing rocks. So, we use Google Earth on my Mac to do a lot of our planning. Once out in the field, I like to have the same data on my iPhone, too. But that’s a bit tricky.
Here are some tips and tricks that I have learned about using USGS data.
USGS data, KML files, and Google Earth
The USGS digitizes geologic units in Keyhole Markup Language (KML). KML is a text format that uses an XML schema originally created by Keyhole, Inc, the original creator of Google Earth. (Google acquired Keyhole in 2004.) Google Earth is free–meaning there is no financial cost to download and use it–and can open and render KML files. (An alternative to Google Earth is the Free Software project called Marble.)
KML file extensions: .kml or .kmz
KML files can get quite large, especially when it comes to mapping a whole state’s geologic terrain. For that reason, KML data is frequently found in a compressed (zipped) version with a .kmz file extension instead of .kml. Both are referred to as KML files. Google Earth can use .kmz files directly, without being first unzipped.
Getting the USGS KML File for Your State’s Geologic Unit
The USGS provides geologic unit data for each state on their website as KML files. Open one in Google Earth, and each geologic unit’s regions display as opaque colors layered atop the terrain. Zoom into an area and click one of these colored units open a balloon showing the info contained in the KML for that unit. The data is pretty lean, but the Detailed Information link in it will take you to the USGS web page containing more information.
Using USGS Data on the iPhone
Can you put USGS data on your iPhone? Yes.
I have found a couple ways to do this, each with its pros and cons.
There’s an App for That
This is essentially one of those apps that just re-packages public domain data. What makes Geology UT any different from Geology CA? Essentially, it’s the data (USGS, mainly) bundled with the app. At $7.99, it’s not too steep for the functionality it provides. Unfortunately, Integrity Logic has yet to update it (despite having graciously thanked me for providing several ideas for enhancement).
To be sure, this app is not nearly as slick as Google Earth. The main advantage of using this app is that it works offline (unlike Google Earth), and includes descriptive data from the USGS website that is not in the USGS KML files. If you work in the field, far from a cellular signal, I definitely recommend this app.
Using KML Data on the iPhone in Google Earth
To be sure, Google Earth on the iPhone presents a challenge when it comes to using KML files, but by no means an insurmountable challenge. Here’s how to make KML data usable through the iPhone edition of Google Earth.
* A Google account
* Google Maps (maps.google.com)
* A Computer with Google Earth
* An iPhone with Google Earth on it
* USGS KML file
You’re going to use the Google Maps feature called “My Maps” to import the KML file. Then, you can use Google Earth’s My Maps feature on the iPhone to see the data.
There are a couple inconvenient issues to get around. First is the 10MB maximum file size that you can import. This restriction applies to the uncompressed file size, which may prevent you from importing. The .kmz for Utah is 6.9MB, but it contains 25MB of data when uncompressed. Second is the default opacity of the data layers. These big, opaque shapes mask the underlying terrain, which is inconvenient. I’ll show you how to get around both of these obstacles.
- Download the USGS KML file that contains the data that you need.
- Open the file with Google Earth.
- All of the geology data will display on the landscape in numerous opaque layers. It will also display in the left-side Places navigation.
- Right-click the unit that you want to add to your phone, and select Get Info from the menu.
- Now, go to the Style/Color tab and set the opacity to 50%. (Also, you may want to change the color to something that will show up well in Google Maps, given the iPhone’s small display.)
- Once you have set the color and opacity to your liking, you can export that unit as its own, self-contained KML file for that unit. Right click the unit again and choose Save Place As… and give your file a name. This should yield a file that is well below the 10MB import restriction imposed by Google Maps.
- Now open a browser and go to Google Maps. (Make sure that you have logged in with your Google Account.)
- Click the My Maps link (on left, near Get Directions).
- Click the Create new map link.
- Create the Import link, and upload the file that you saved from Google Earth.
- Before clicking Done, consider whether you want this map shared. (Google Maps will default to Public.)
- After clicking Done, you will see the geologic unit in Google Maps. (If it appears to be incomplete, scroll down through the list of elements at left, and you’ll see why: Google splits the list into multiple pages. Google Maps is not very good for viewing numerous polygons that often comprise a geologic formation.)
- At last, it’s now time to get your iPhone and open Google Earth.
- Click the Options button (i) in Google Earth.
- If you have not already done so, log in with your Google account. Once you have, you can use My Maps to enable the map you just imported into Google Maps.
And with that, you have brought USGS geologic units onto your iPhone.