it will take you more than 3 seconds just to eye up the end, place your stick on your nose and look down.
spoken like someone who has never taken the time to learn to use a laser measuring device properly. i could easily use my disto to measure your second scenario. the plus and minus functions on the disto were designed for situations like you describe. start at one end of the dormer (typically the end that is in the middle of your garage door), measure to where the garage door ends, hit plus, measure the last 2-3 feet. poof. done. no need to stick anything on my face or look at the ground. there is ALWAYS something to measure against with a disto, you just have to be smart enough to figure out what it is and intelligent enough to use it properly with your disto.
no point in splitting hairs, to each his own. some can adapt to new technology and improve things, some can't or won't.