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Nothing has so radically transformed GIS as the 2005 release of Google Earth. Google Earth combines a very simple yet powerful interface with stunning graphics and a planet full of data to which anyone may add information and share that information with the rest of the world in just a few short clicks. Because of its simplicity and power, it has become widely adopted in a relatively short time. It is simple to use, fun, and stable.

Google Earth has revolutionized GIS by providing a free and simple-to-use GIS application that anyone can use. Requiring only a good Internet connection and a 3D-capable graphics card, it provides global aerial imagery at varying scales. Users may download the application, which is free for personal use, or $400 for professional or business use. Google Earth works by connecting to the Internet to stream data to the users. The user has a few simple tools to control navigation such as pan, zoom, tilt (for 3D perspective). Other features allow the user to enter an address in a variety of formats (street address or coordinates) and then zoom to that location.

Additionally, users can add their own georeferenced data to display in Google Earth. The required format is Keyhole Markup Language (KML), or GPX (GPS exchange). KML is a simple text-formatted syntax that provides basic information regarding location, data type (points, lines, polygons), symbology, and attributes. Many free utilities will convert data from one type or another into a KML format for use in Google Earth. Surveyors may be interested in converting data from AutoCAD, Microstation, or ASCII formats into KML. Autodesk provides a free utility to convert AutoCAD data (from certain versions). Bentley Systems Inc. provides a utility for its Select subscribers. One need only search the Internet for a utility to convert from your favorite format into KML or GPX format suitable for Google Earth.

GPX format is compatible with some GPS devices and uses XML schema for describing waypoints, tracks and routes. Google Earth will accept GPX data. For example, one may easily convert NGS datasheets (DAT) with very simple converter to GPX format. In this way the location of NGS points may be displayed in Google Earth (see Figure 1). Note that Google Earth provides a To Here/ From Here directions option within the point feature balloon. This handy tool provides driving directions on how to get to or from the point. GPX is a simple format for integrating GPS compatible data that will display in Google Earth. Free utilities exist that will convert KML format data to GPX format, which one may then upload to a GPS device. With the data loaded into a GPS device, one can then navigate to the point.

I opt for a more robust solution to representing NGS points in Google Earth. I find that integrating my own data with Google Earth is very simple to do, and is a powerful tool for providing context and location that are helpful for planning projects. In the following example, I extracted National Geodetic Survey (NGS) data for Yellowstone National Park, in order to see where geodetic control was available within the park. To do this, I downloaded the NGS points for an area in shapefile format, which I then loaded into ArcMap. There are a few free KML converters available for ArcMap. The utility that I used allowed me to select which attribute to use to label the points (I used the Station Name), and which attributes I wanted to show in Google Earth. I was able to bring in all the attributes provided by NGS or only those that I selected. Once I had created the KML file, I merely drag and drop it into Google Earth. Google Earth then automatically zooms to the spatial extents of the points that I loaded.

Within Google Earth, I can click on a point to list the attributes of the point. If I had included the DATA_SRCE attribute, then I can also click on that attribute, which is a hyperlink to the NGS datasheet. That sends a request to the NGS server to pull up the data sheet for that particular point (see Figure 2). This is a very nice feature because the KML files are typically compact and small enough to e-mail, yet when I want the full datasheet, I can readily get it, and more important, when I click on the hyperlink I get the latest datasheet. With the NGS points in Google Earth, I can see where the points are located, how to access them, whether or not they are likely to be open to the sky or traffic issues, etc. In addition, I can zoom around the points and look at them in perspective view or see from them from any angle. Although this is a more complicated path to getting NGS points into Google Earth, I find that the end result provides me with a more useful solution. The ability to hyperlink to the latest and most up-to-date datasheet is important for obtaining the more recent information on recovery, coordinate adjustments, and any other information that may change.

In addition to points, Google Earth will also take lines and polygon overlays. Polygons are useful for features that cover an area, and the polygon itself can by symbolized with a solid color or a transparency. One may, for example, convert zoning to a polygon KML feature then overlaid in Google Earth (see Figure 3). An agency or company could communicate project information such as the location of sewer and water lines for a development project using Google Earth.

Because KML and GPX files are usually pretty small, they can easily be emailed, or they can be shared by posting them on a website for others to access. This means that sharing your GIS data with a client or colleague is very easy to do. Google Earth is a rich and powerful tool that makes it easy to use GIS and to share GIS information with others. Because of this, Google Earth is putting GIS in everyone's hands.

Rj Zimmer is the GIS Director for DJ&A, PC a surveying, engineering, and mapping firm in Helena, Montana.

A 511Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE