SOS - Day Time Ground to Air Signals It is pretty amazing that in all the lost hikers in the wilderness situations we have seen in the last six or seven years, none of them were located by, or used a ground to air signals.
Sometimes called a Ground Activation Signal (GAS) or Recovery Activation Signal (RAS) by military search and recovery doctrine and protocols, this is nothing more than a giant signal, almost always a letter, on the ground visible to searching aircraft. And by giant, I mean not a six foot long letter but a 30 foot long letter - the bigger, the better.
Military personnel who are lost or evading the enemy, often carry highly visible panels, called VS-17 panels. These are Orange or Yellow on one side and Carteuse (pinkish) on the other side that can be used to signal aircraft or as a recognition signal to let aircraft know it's safe to land. Many military members choose to carry a yellow or orange colored 3 foot x 3 foot cloth, such as a parachute for a flare, rather than the bulkier VS-17 panel.
But no matter what day time signaling aids some soldiers carry, they are go on missions knowing what code letter to use as the GAS or RAS if they find themselves in a survival or evading the enemy situation.
This code letters are usually published to all military units and changed once a week, but if you are a missing soldier when the new code letter GAS/RAS comes out, your previous code letter is valid since personnel and units looking for you will know you are on the old letter.
Lost and surviving civilians can take a page out of this military search and recovery book by using a large, code letter to attract the attention of searching aircraft or even aircraft just passing by. Remember this has to be LARGE and visible from the air. It can't be an "I" or an "O". Rather, a "W", "K", "A" or an "H" would be more distinguishable from the air.
Your imagination (and physical ability) are your tools. Natural objects are your materials. The GAS/RAS code letter needs to be as different as distinct from the adjacent land as possible in color as searching aircraft may be looking for you at first or last light where shadows may be your enemy, or during the middle of the day when the Sun bleaches things out.
Rocks, sticks, logs, and cleared dirt are all good possible materials for a code letter. And if you vacate the area, leave the code letter up with an arrow showing your planned direction of travel.
Stay Prepared! Stay Alive!