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A little background on it: The story of Google Earth actually starts with a network of satellites. In the 1970s, the US government used a set of satellites known as "Keyhole" satellites to scan sections of the Earth's surface. The image below (from Wikipedia) shows an illustration of the Keyhole satellites circa 2013
Source: https://en.wikipedia.org/wiki/File:KH-11_Keyhole_constellation,_September_2013.png
This data was typically used for intelligence purposes (e.g., tracking construction activity in the Soviet Union or its client states). Starting in 2001, this data was eventually bundled (along with aerial photographs and GIS data) into a dynamic globe by a company called Keyhole, Inc. Google bought this company in 2004, and released the dynamic globe to the public in 2005.
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Getting to know the software as an end-user: Google Earth (and other geospatial software) does not have the same grammar as the productivity software that you're probably used to (e.g., word processors, slideware, spreadsheets). True, there is a File menu, an Edit menu, a View menu, etc. The way it works with data, however, is very different, and even the layout of the features is different.
I have a heuristic for exploring geospatial tools: LINIQES. This stands for Load, Interface, Navigation, Inquiry, Query, Edit, and Save. (There's sometimes an Organize step between Edit and Save or a Share step after Save. But LINIQEOSS just sounds crazy....)
You load Google Earth like anything else: Launch it from your Applications list or Programs folder. One thing to keep in mind is that it needs an Internet connection to function–it loads data from Google's servers and sends queries back there.
Next, let's look at the interface. I divide it into four regions, abstracted in the diagram below.
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- Points (e.g., a pushpin) – Google Earth calls these "Placemarks"
- Paths (either a straight line or a curve made up of multiple line segments)
- Polygons (and area bounded by lines or curves; can be filled in or not, or given a transparent fill
- A 3-D model. These can be built in SketchUp (also free from Google: go to sketchup.google.com) and imported
- Image overlays (e.g., stretch a historical map over the contemporary satellite image)
- ...and more, which we will get into later.
However, adding features is the easy bit...the hard bit is editing the features after you've added them. Let's say that you've placed a pushpin and now you want to adjust its placement, or re-color it, or pick a different icon, or change the label or caption. How do you do that??
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Advice: Use the kmz format. I can't imagine a situation in which you would want to have the kml instead. Exception: As of this writing, ArcGIS.com will work with a KML but not a KMZ. If you're making a Google Earth file for the purpose of pushing it into ArcGIS.com, you'll need a KML.
Ready to start marking it up?
- List of bookmarks related to Google Earth: https://deliciousdel.icio.comus/tchammond/tlt394,+GE
- A one-page handout I created to help middle school students (and you!) with Google Earth: Google_Earth_howTo.pdf
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