If you use Garmin MapSource you’ll get the speed and timing from an exported track, no need to calculate it from the coordinates (which can be somewhat tricky).
Using a spreadsheet program you’ll be able to create text based keyframe data from the log.
If you can’t find any posts or tutorials on text based keyframe format, do this;
Create some rotation keyframes in AE, copy them and paste them in a spreadsheet program. You’ll see how to format your GPS speed data to make rotation keyframes. Once you’ve done that you simple copy the text and paste it on a layer.