Hello Mason,
Pleased to meet you. I’m a high school teacher here in Austin, TX. I’ll try to answer some of your question, but please keep in mind I don’t work nor speak for Google. That stated, I’ve created a few Google Earth files and a Google Maps API website used in education.
Our client is concerned about such a tour's open accessibility (he would like it to be as accessible by as many people as possible) and its longevity. I honestly don't know how to figure out how I'd answer him.
If the audience is K-12 you will want to make sure that the kml works in Google Earth for Web. This will increase the likelihood of the file working for PCs, Chromebooks, Android, and iOS.
You might think about using either Google Drive or <NetworkLink>s ; allowing you to update the file. https://developers.google.com/kml/documentation/kmlreference#networklink
Please note that Icon images, <GroundOverlay>s, <Networklink>s requires CORS headers to be adjusted; allowing the domain earth.google.com/web to access “get” the files. https://enable-cors.org/index.html
There are less than documented kml tags that Earth for web support. (ie. <gx:displayMode>panel</gx:displayMode> ) Feel free to look at my kmls linked in this blog post (All designed for 'new' Earth...Google Earth for Chrome): https://geteach.com/blog/2018/07/30/inner-earth-with-google-earth-and-geteach-com/
Does anyone on this community have any past experience that might shed some light on the broad access possibilities of the different Google Earth platforms for education.
Not sure what you are asking here. I’ve created edu sources using these google geo tools.
Google Maps API: https://geteach.com (4min YouTube Overview)
Google Earth for web (link to my kml files): http://bit.ly/jwilliamsKMLs
Google Earth Engine: Blog Post with link and video
Is there a way to measure how 'popular' content is?
I don’t do this myself, but you might try to embed a Google Analytics tag into an info window. Not sure if the sandbox will block the scripts, but worth a try. If you are using an image from your server, you could track the number of views from that image url. If you use a <NetworkLink> from your server, you could track that.
I'm presuming that any content that's generated for Google Earth education is hosted through Google, but I suppose I could be wrong on that. Does anyone have a more definitive answer?
Yes, you are correct
Also, does anyone have examples of new versus old Google Earth Education content? How long could something like this be available?
Everything I’ve built for Google Earth these past two years focuses only on Earth for Web. I love the desktop version and know it currently has more features. However, I don’t believe PC applications are the future for education…or any enterprise. Again, my opinion; I don’t work nor speak for Google.
Are there any recommendations for the best tools to use to build the tour I had in mind?
I build files two ways.
a. Hand script with Notepad++; using <Style> templates for single images, carousel, YouTube.
b. Create a Google Sheet that creates the kml. (Used when I have a lot of point data and/or complicated kmls like Quizzes)
I am happy to help more. You can find me on Twitter @geteach
Hope this helps,
Josh