I've been working on my private pilots license for the last few months. The primary plane that I've been using is the Cessna SkyCatcher. I've included a photo of an example of this plane below. It's a fun aircraft, other than the fact that two normal-sized adult males can't take full fuel.
One of the nice features of this plane is the Garmin G300 "glass cockpit" system. The days of circular "stream" gauge instruments are fast coming to an end. This particular aircraft's system has a SD-Card slot that can be used to update the databases, store flight plans, and the like. If a card is installed during flight, a log is updated every second. Luckily, Garmin had the foresight to write these logs using standard CSV (comma separated values) files. The logs contain valuable data including not only the location, altitude, and speed, but engine data, faults, and nearly anything that is displayed on the screens. This would be very valuable data in an NTSB investigation, that's for sure.
Because Google Earth really does not care about exhaust gas temperatures, RPMs, and things like that, the first task is to discard all that data. The only data we need to keep is local time, latitude, longitude, and altitude.
It's your choice whether you'd like to use GPS or barometric altitude. They both have their advantages and disadvantages. I usually use GPS altitude.
The website that converts from CSV files to Google Earth files insists that the altitudes are presented in meters, rather than feet. Even if you select "U.S." or "Nautical" units in the interface, it still processes the altitudes as meters. To execute this conversion, I make a new column that is computed from the altitude, multiplying it by 0.3048 which yields meters from feet. Then, depending on your spreadsheet program, copy this new column's values on top of the GPS Altitude column, then delete the computed altitudes.
Next, we need to add a track point column that's numbered serially. The easiest way to do this is by using another function that creates this data from the
ROW() function. Also, we can use this time to rename the columns; they need to be named a certain way for the website.
Processing the log is all finished. Next, just export it from the spreadsheet program into a new CSV file.
Almost last step: We go to GPSVisualizer.com and navigate to the Google Earth KML file form.
The important fields to change are the document name (this can be whatever you want, it'll show up in Google Earth), the Altitude mode (set it to "Absolute"), and finally choose the CSV file that you've carefully modified. When you click "Create KML file" you'll be presented with a screen that lets you download your new KML file. Once it's downloaded, assuming that you have Google Earth installed, it'll open and you can move it from "Temporary places" to "My Places" and it'll be saved. The end result is the nice image at the head of the article.