Although land, sea, and aerial [unmanned vehicles] are available, for the purpose of survival ‘hobbyist’ surveillance from an aerial vehicle is the best option. A land or sea based homemade ‘drone’ would have to be large to navigate even moderate terrain or choppy water and the larger the vehicle is the more costly, dangerous and obvious it is. Aerial ‘drones’ on the other hand can be much smaller and unobtrusive. When we refer to drones, what we are really speaking of just a radio controlled vehicle with perhaps some fancy telemetry. Aerial drones come in two basic flavors, fixed wing and multi-copter. I have experience building both as well as automated lawnmowers and snowplows.
A fixed wing UAV is really a radio control airplane. There are thousands of models available, from palm sized to nearly full scale. Power can come from a battery or even a small scale jet turbine. The best format for a drone would be an inexpensive expanded foam model. These foams can withstand full speed impacts with the ground with really no damage other than a broken propeller (trust me I know). Skillfully built and operated, the fixed wing drone could stay aloft for hours and several thousand feet up. Operation is nearly silent when at altitude.
A multi-copter is just a helicopter with more than one rotor. A Chinook is an example of a full scale multi-copter. Multi-copters come in several formats, having from 3 to 12 motors on arms extending from the center. Kits are commercially available, or a good multi-copter can be scratch built at home. Design can be very robust if proper materials are selected. The strongest units are made from carbon fiber or aluminum, with motors oriented for redundancy. My multi-copter is about 4 feet across, weighs 6 pounds, and can lift a 4 pound payload. These are very versatile. I can follow a car, land on a roof, even fly to my front window and look inside the house. Multi-copter electronics are much more expensive than their fixed wing counterparts. Careful consideration must be paid to electronics protection.
This is a bit of a catch all term and can best be divided into stabilization and flight control. For a fixed wing vehicle, stabilization can be done inexpensively with hobby gyros. This will automatically correct the flight to straight and level after any deviation. Flying is much more simple. Flight control is added on top of stabilization. Generally flight control is via GPS radios with waypoints programmed via a computer. You end up with a radio controlled airplane that once launched will fly, to a point(s) and circle, take video, etc. and fly back. Video feed is also possible, but even a cheap video camera will record nicely from the air.
For multi-copters stabilization is absolutely necessary. Humans can not control anything this complex alone. For a multi-copter the stabilization essentially compiles normal inputs, from a radio or flight controller, along with gyro and accelerometer data from the vehicle. The stabilization computer then calculates the desired speed for each motor. Multi-copter stabilization is very effective. I can literally shove my x8 multi-copter in flight and it simply autocorrects back to its original position and heading. Multi-copter flight control is very similar to fixed wind control, via GPS waypoints, although ultrasonic range finders can be used indoors. The stabilization in my multi-copter is capable of controlled flight in 25+ mph winds.
Please keep in mind that there are FAA and FCC rules governing radio control aircraft, drones and video downlink radios.
After months of tinkering, crashing and spending probably thousands of dollars, you will have a drone that will fly in a stable manner. You will be able to control it with your radio and maybe you invested enough for a flight controller and video down link. What do you do with this new toy?
Due to payload and range restrictions, an aerial drone is not suited for really anything other than surveillance/reconnaissance. Honestly, in a survival scenario, my multi-copter in not even on the bug out list. That is not to say that these things are useless to a prepper though. I have video of my house and neighborhood. I can easily fly above and look down undetected. If I wanted to, I could peer into window on a high rise. Whether bugging in, or at a retreat a bird’s eye view of your environment is very much a force multiplier, although I sometimes think a camera on a $10 kite with a long sting is an equivalent option. Regards, – Rockhound