You found this on the internet.  Treat it appropriately. 

SARMath.com is not an authority on Search & Rescue.  Many of us are affiliated with SAR teams, but not all.  Before you rely on anything during an operation, thoroughly research and test it.  Then train with it over and over.  If you would like to get involved with Search & Rescue, contact your local Agency Having Jurisdiction and ask how you can help.