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Developing Google Earth Tours

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Overview

Google Earth tours (such as Palisades 2010) are developed on your desktop using the Google Earth application and then saved as KML (or KMZ) files. The KML/KMZ file must then be posted on a web server somewhere and its URL passed as a request parameter to the VRMC Google Earth Player (e.g., within the HREF attribute of a link posted on your blog). There is no need for the KML file to be hosted on the VulgarianRamblers.org site, but it does need to live on a web server. If you don’t have access to a web server, you can always email your KML file to me.


Building Tours

OK, so it’s not trivial, but once you get the hang of it, tour building is fun.

To build a tour, you need a recent version of the Google Earth application, a considerable amount of free time, and even more patience. You begin by creating a series of placemarks (each with its own camera perspective). Once you have these placemarks (and other appropriate content) defined, you record a series of user actions where you double-click on each placemark in turn, causing Google Earth to “fly” the camera smoothly from one perspective to the next. It’s also possible to simply create a tour object from the placemarks within a folder, but I find that you often need to use placemarks more than once. Recording your placemark selections by hand also gives you a little more control over how the jumps are stitched together (though not very much).

The most frustrating part is that this recording step takes a few minutes, requires a series of flawlessly performed and well-timed user actions, and must be re-done from scratch if you make a mistake or want to change the sequence later. You can’t edit the tours themselves, only re-record them. Finally, although the KML files are just XML, you won’t want to edit them directly. Google Earth records a ton of smaller jumps between each placemark view, so the tour portion of the KML file is huge and complex. Also, any edits you make to the KML file will be lost the next time you export from Google Earth (an operation you’ll likely be performing multiple times).

Still interested? Read on...

Importing Content

I think including the California Thirteeners (and non-Thirteeners) placemarks makes a tour through the Sierras more interesting and relevant to climbers. To do so, go to the California non-Thirteeners page and click the “download the list’s KML file” link to get all of these placemarks onto your hard drive (and into your Temporary Places folder within Google Earth). Create a new tour folder within your My Places folder (i.e., click My Places, then select Add>Folder), giving it an appropriate name (e.g., “Palisades 2009”). This new tour folder should contain all of the content for your tour, so drag the California Thirteeners folder into it (from your Temporary Places). You can add content from other sources too, though (unfortunately) it’s not possible to add things from your Layers database.

Adding Placemarks

Create another folder within your tour folder named “Placemarks”. Use the Google Earth controls to place the camera in an appropriate position from which to view the location where your trip begins. Make sure your Placemarks folder is still selected and then select Add>Placemark. Type a name for your placemark in the New Placemark dialog box that appears, but don’t close the dialog box yet as it must be displayed in order to modify any attribute of a placemark. Reposition the placemark icon in the approximate location where your trip begins and then click the OK button. If you need to change anything about the placemark later, just right-click the placemark (or its entry in your Placemarks folder) and select Get Info to bring up its Edit Placemark dialog.

Warning! Google Earth doesn’t ask you whether you want to save the changes you made to Placemarks, Paths, etc. if you click the Get Info window’s close box. I imagine Google will fix this bug eventually, but for now you should be careful to click the OK button after you’re finished editing an object.

You can copy the current camera view parameters into a placemark by right-clicking the placemark (with no dialog displayed) and then selecting Snapshot View. You can even adjust the camera view parameters in the View tab of the Edit Placemark dialog, but I find that using the standard Google Earth controls (and then applying the snapshot) is much more natural. You can select a different placemark icon (or choose to have no icon at all) by clicking the icon in the upper-right corner of the dialog. You can even hide the placemark completely (essentially defining only the camera view) by selecting no icon and then setting the opacity of the label to 0% (in the Style, Color tab of the Edit Placemark dialog). Such hidden placemarks will still appear in your Placemarks folder.

Note: The next placemark you add generally inherits the display properties from the previously created/edited placemark, which can be confusing if the previous placemark was hidden.)

Note: You should pick an appropriate camera view for each placemark you add. You’ll probably be creating placemarks (e.g., for nearby lakes) that you won’t actually be flying to during the tour, but it’s hard to predict exactly how you’ll choose to fly before hand, so it just makes sense to have an appropriate view for each object in your KML file (even the folders).

Warning! You should always fly to a Placemark (by double-clicking it) before you edit anything about it, because Google Earth will sometimes capture the current camera view along with any changes you make (i.e., even if you don’t explicitly select Snapshot View).

Finally, you may wish to add descriptive text to some of your placemarks (displayed in a balloon when you fly to this placemark in your tour). I think these guys can be annoying while the tour is playing, so I’ve started adding them only to objects I don’t fly to during the tour.

The balloons for the Thirteener placemarks incorporate HTML making explicit reference to and use of the CSS on the VulgarianRamblers.org site (and the underlying KML takes advantage of features not available within the Google Earth UI). Even if your descriptions are plain text, the plug-in apparently applies the VRMC CSS to your placemark balloons as well (in a rather naïve manner). As a result, plain text descriptions will be displayed using center alignment below a centered grey placemark name. You can tweak this behavior a little by incorporating HTML in your placemark descriptions (e.g., just bracketing each description with “<p align='left'>” and “</p>” tags).

Note: the description balloon only appears if you double-click the placemark label (within the Placemarks folder). Double-clicking the first two lines of text that appear just below this label will fly to the placemark without displaying the balloon. This may be useful if you have to return to the placemark during your tour.

You should test out how Google Earth flies from one placemark to the next by double-clicking them in your Placemarks folder. To fine-tune the flight between two placemarks, you may need to add another (hidden) one in between them. Unfortunately, doing so generally adds to the length of your tour.

Adding a Path

Since trails are not among the standard set of layers available to the plug-in, you may want to indicate your route using a path, which is just a series of line segments linking points on the ground. Make sure your tour folder is selected, then select Add>Path. Type something like “Little Lakes Valley trail” into the New Path dialog box that appears, but don’t close the dialog box yet (as it must be displayed in order to modify any attribute of a path). Start constructing your path by clicking the mouse in a series of locations. You can adjust the location of any point by carefully clicking and then dragging it. Whenever you click outside the bounds of any existing point a new point is created immediately after the currently selected (blue) point. This usually means the path will be extended from the last point (i.e., the one furthest from the start). However, you can add a point between two existing points by selecting the earlier one (i.e., the one closest to the start) and then clicking some location between them.

Note: In addition to clicking to create a new point, you can also click and drag to create a series of points. However, I find that doing so creates too many points for me to have good control over the path. I just mention the feature here in case you drag a little after your click by mistake and are confused by the results.

You will soon find that developing the path requires you to constantly adjust the camera view so that you can see where to place the next few points. You can use the Google Earth controls for this, but you’ll also find yourself temporarily closing the Edit Path dialog, adjusting the view (e.g., by double-clicking a placemark and then fine tuning your perspective), right-clicking the path in your tour folder, and then selecting Get Info to begin editng the path further from this new perspective.

Note: Often your path will follow an official trail, and sometimes these trails are already available if you dig through the Layers database (the contents of which is apparently controlled remotely by Google and changes daily). As mentioned before, you can’t copy one of these into your KML file, but you can create a Path to follow it. I find that trails selected via the Layers database are more visible from at least a 1200m above, whereas the trails themselves are easier to find in the terrain from a viewpoint just above the terrain (ideally from the same perspective that the original photography was taken from). When you’re satisfied with your path, don’t forget to choose an appropriate camera view, usually one that shows the path in its entirety.

I’ve been experimenting with color coding my paths to indicate their difficulty (e.g., blue for Class 1, green for Class 2, etc.) I’ve been setting the width to 4.0 for trails and 2.0 for cross-country routes.

Recording the Tour

Once you have all of your placemarks ready to go, double-click the first one to position the camera at the beginning of your tour. Review your placemarks so that you’re quite clear how they should be sequenced, then select Add>Tour to create the new tour object.

Click the record button in the controls that appear and then immediately double-click the next placemark in your sequence. Once the camera arrives there, double-click the next placemark and then repeat this process until your tour is complete. At this point, click the record button again to turn off recording. The playback controls should appear and your tour will be reviewed once.

If you’re satisfied with the result (unlikely) make sure your tour folder is selected, then click the disk icon in the playback controls, type something like “Fly-through tour” into the New Tour dialog box that appears, and click the OK button. Unfortunately, the name is really the only thing you can edit after the tour has been recorded.

Note: While recording a tour, you may find that pausing at a placemark for a second will allow placemark labels and other content in your view to be displayed (though this seems to be somewhat network dependent). You may also find that skipping on to the third placemark before you completely arrive at the second one will provide a better flight path, depending on the circumstances.


Expectations of the VRMC Player

Once you have all of your content built, you should organize it so that the VRMC Google Earth Player has access to everything it needs to play your tour properly. The player makes two special expectations of each KML/KMZ file passed to it:

  1. The name and description from the first feature within your KML file will be used as the heading and first paragraph displayed above the panel where the tour is shown. Because folders are a type of feature, this should be your tour folder (e.g., “Palisades 2009”).
  2. The player will conduct a breadth-first recursive search through all of the folders in your KML file until it finds the first tour object, which it will begin playing immediately.

All of the placemarks and paths in the KML file will also be visible while your tour plays.

Here’s a suggested arrangement of items within your tour folder:

  • Tour folder (e.g., “Palisades 2009”)
    • Tour object (e.g., “Fly-through tour”)
    • Placemarks folder (containing all of your placemarks and paths)
    • California Thirteeners folder (containing placemarks for all Thirteeners & non-Thirteeners)

Saving and Posting Your KML

Select your tour folder (e.g., “Palisades 2009”), select File>Save>Save Place As... and then give the KML or KMZ output file an appropriate name and location on your local hard drive. Upload this file to the web server you have access to. It’s usually a good idea to avoid spaces and other special characters in a file name destined to become part of a URL.


Launching the VRMC Player

The VRMC Google Earth Player lives at http://www.vulgarianramblers.org/tours/google_earth_player.php, but you must specify the location of your KML/KMZ file in the kml_url request parameter. For example, if your KML file was located at http://www.acme.com/killer_tour.kml, then the URL for playing it would be:

http://www.vulgarianramblers.org/tours/google_earth_player.php?kml_url=http://www.acme.com/killer_tour.kml

Therefore, you could simply post this URL on your blog or send it to your friends in an email. Note that the VRMC Google Earth Player should automatically guide the user through downloading and installing the Google Earth plug-in if it is not already installed in the user’s browser.

Warning! The Google Earth plugin apparently caches KML/KMZ content in a non-obvious way. Thus, you may find that after posting an updated version of your tour, the old version still plays in your browser. Clearing the Firefox cache doesn’t seem to solve this problem, unfortunately.


Other Resources

You may find the following resources useful as well:

Good luck with your tours, and please let me know if you discover any other useful tricks (or have any feedback on this guide).