I'm amazed at how much of a difference MB Gravity (elevation correction on Motion Based) makes on elevation measurements. Here's two runs on the same out-and-back course (which should have a symmetrical elevation profile). Here's the un-corrected version (directly as the Garmin sees it): Here it is corrected by MB Gravity: Huge difference! If you use Motion Based, bu sure to turn the corrections on. I was especially concerned about the huge 300' cliff around the 3.25 mile mark. You think I would have remembered that.