Using Google Earth

This site uses Google Earth to display maps showing bike rides (loops) and area roads. On each blog post just below the map showing the ride there is a link to download a file which will show the ride in Google Earth. The map shown on the blog post is displayed in Google Maps (not Google Earth). Many of the features of the Tuolumne Bikes map won’t display correctly in Google Maps, so you need to download the file and install Google Earth to get the full benefit from the site. The downloaded map will have every loop from all of the blog posts on it and all of the roads that have been mapped to date.

Download or update Google Earth for free: http://www.google.com/earth/download/ge/

After installing Google Earth, click on the link on the  blog post to download the map file (bikeridename.kmz). After you click to allow the download and run the file, the map will open in Google Earth. Google Earth has an intuitive user interface and the map has built in help features, but if you have problems, these tips will help you get the most out of the maps.

The most useful functions within Google Earth are available within the Places panel, by clicking on the map, or by navigating using the controls in the upper right corner of the map.

Google Earth screen shot showing controls

When the map loads in Google Earth, the file will be listed in the “Temporary Places” section of the Places panel. There is also a section for “Layers” below “Places”. Most of the layers are not important for using the map; you can click the triangle next to “Layers” to collapse the section and then drag the bar separating Layers and Places downward to make more room for the map information.

The loop from the blog post should be checked, the rest will not. Roads are displayed on the map as a series of colored segments showing the road surface and traffic; the selected loop is highlighted in blue. You can turn the loops and road segments on and off by clicking the check boxes in the Places panel. The loop names are links to the blog entries, so you can navigate through the blog by turning on loops and clicking on those that interest you. There are little green bicycles on the map which you can click for information about the roads.

By default, Google Earth displays the blog posts through its built-in browser. You’ll get better results and be able to display both the map and blog at the same time if you set Google Earth to open your browser to view web page links. Use Tools>Options>General and check the “Show web results in external browser” checkbox.

The “Map Search” link in the right sidebar on the blog provides a map that doesn’t focus on any particular route. Click the loops checkbox to turn on all the loops and zoom to the area you are interested in. The loop titles on the map provide links to the blog posts.

If you right click on a loop or road segment in the Places panel, you can choose “Show Elevation Profile” from the context menu that pops up. You can also right click the loops or roads on the map, but you may need to turn off some roads or loops, so you don’t get the profile of the wrong map feature. Note that loops are in folders in the places panel; “Show Elevation Profile” is not in the context menu for folders–you need to expand the folder to find the loop segments inside and right click on them.

GE elevation profile

As you slide the slider bar along the profile it shows the elevation and percent slope both on the slider and on the red arrow that traces the route on the map. The profile of the full loop also shows the length of the ride and total climb. I expect that the total climb is somewhat overestimated–Google Earth is comparing the route to a 3-D map of the terrain that is neither 100% smooth or accurate, so the profiles are somewhat jagged. When summing all the ups and downs, the up and down errors accumulate which overestimates the total climb. The effect is worst for the flattest routes like ditch trails and railroad grades.

Holding down the left mouse button to drag the mouse along the profile will select a segment of the profile and display the length and slope data for only that segment. This provides a handy way to find the length of paved or dirt segments by watching the arrow on the map while dragging on the profile. The Google video on this page: http://support.google.com/earth/bin/answer.py?hl=en&answer=148072&topic=2376756&ctx=topic
includes a demonstration of the elevation profile feature.

Fiddling with the navigation controls will get you going with 3-D visualization.

If you get lost, double clicking on a loop will center on the loop with north up. View>Reset>Tilt and Compass is also handy.

The image above shows Google Earth with a Google Maps overlay set to “Terrain”. I prefer the terrain maps to the aerial imagery, because I can see the roads better, but the long-term stability of map overlay applications for Google Earth hasn’t been great. Of course these are free applications, so how much can we complain? I don’t know why Google doesn’t make their standard map types available as built-in imagery options in Google Earth. There is a working map overlay application available at http://www.mgmaps.com/kml/. Click the maps.kml link to download the file. Open the file and save it to your My Places and you will have a wide variety of map overlays to choose from any time you use Google Earth. Alas, the Google Terrain overlay does not work. The maps don’t always reload properly when zooming or panning–right clicking on the network link icon next to the selected map in the Places panel provides an option to force a reload.

The little golden person at the top of the zoom control in the navigation controls is used for Street View. Drag him or her to a road; if the road turns blue you can drop him or her on the road to access the Street View imagery.

Don’t expect Street View for remote or dirt/gravel roads. If you have spare time, you can hold down the up arrow and “drive” the route at a slow and somewhat blurry pace. If your Google Earth doesn’t have Street View, you need to update.

Use File>Print>Screenshot of current 3d view to print the map. Try File>Save>Save Image to save whatever is in the current map window as a jpeg. This works for printing the map and elevation profile and it gives more options for print layout–just print the jpeg from your favorite image viewer.

You can save the map in your “My Places” list if you wish. If you have already saved the .kmz file on your computer you don’t really need to do this since you can just open the file. If you want to see what’s in the .kmz file, change the extension from .kmz to .zip, open the file, and view it in a text editor.

The files available for download on the posts contain a “Network Link” to a master “loops and roads” file which is downloaded live each time the map is opened. This ensures that you always get the latest version of the map even for the older posts. The downside of this is that you need a live internet connection to view the map. If you have a need for a static version of the map (for your portable gizmo, perhaps) that is available: loopsandroads.kmz.

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