KITE AERIAL EQUIPMENT
KAP is simple. You need a kite (no, really) and a camera - and then you wait for the wind. That said, the devil - or, to be more precise, good kite aerial photography - is in the details.
First, about them kites. As a general rule, bigger is better: it is not so hard to lift an action camera (a Go-Pro or the like), or even a compact camera, but a good MILC or DSLR can weigh well over a kilo. And yes, the difference in quality of pictures is huge. Sometimes you want to lift two cameras (like one for video and one for stills), or an IR camera or even a LIDAR system - and bigger is definitely better ...
... up to a point. A 3m diameter kite in a moderately strong wind can create so much pull you wouldn't be able to bring it down on your own (yes, KAP is even better if you do it with someone). There are limits of the frame (even kevlar can handle just so much), of the fabric and ot the line. Top end material is expensive, and scrooging is not a good excuse when your kite with an expensive and heavy DSLR attached crashes down (on somebody's fragile head). We did our kites ourselves - cutting, sewing, glueing - using probably the best materials there are: the fabric is used for sails, all spars are thick kevlar or carbon fibre, the line can hold 100+ kg etc. etc.
As the wind blows in different ways, there is no single 'best' kite design. Kites that can fly in light breeze are completely untameable in a strong, turbulent wind. Those that easily handle 50 km/h wind will drop like a stone in 10 km/h wind. Turbulence-resistant kites dance like mad in a constant wind. As a tried-and-tested rule we use three different kite designs that cover most of wind types around here: a hexagonal Rokkaku for light to moderate winds, a classic Delta for moderate to strong winds, and a sparless Royal 69 sled kite for stronger turbulent conditions.
There are other considerations. Some kites fly higher (a good delta can easily do 60°, even 70°+ angle), some go far before they get to an altitude. Everything depends on your motif: if you can get close to it, a high-flying kite is cool. If you can't get close (shooting a forest, a swamp, an island on a lake and such), a low-angle kite is best.
Rokkaku means "hexagon" in japanese and is an old, tested and reliable design. Not the easiest design to make and assemble (two spars must be bent to achieve smooth flight, and the four-point line attachment can be confusing), but far from being complicated. Our 200 cm blue Rok reigns supreme in the lightest breeze, handles moderate turbulence excellently and is like nailed to the sky in constant wind. It is a great-but-compeltely-manageable-pull, moderate-capacity kite that needs some encouragement during lift-off, then practically flies itself at altitude. Tame like a kitten in light to moderate winds it becomes a crazy monster in over 30 km/h wind: monitor the speed and pull it down before you get pulled up. Flying angle is adjustable and goes from 30° to 60°.
A classic, strong-willed high flyer. Easy to cut, sew and assemble. Great for moderate to strong winds and best when high flying angle is desired. It lifts off almost by itself, but can be restless higher up, tends to overfly (not good) and is prone to sudden reversal that can end in crash or CFIT. A tail (both open-ended or attached to both corners) remedies that in exchange for a somewhat lower flying angle. Harder to handle than a Rokkaku, it is a high-pull, high-capacity kite that fascinates every time. We have a 300 cm Great White Delta and we still go 'wow!' when it hits the winds.
ROYAL 69 SLED
This is a relatively new, sparless design, difficult to sew but easy to assemble - being sparless it is ready-to-fly. It is great for moderate to strong winds, handles turbulence exceptionally well, and likes to dance and sway all around the sky. Low flying agle, great pull and high capacity. Perfect for areas with unpredictable and difficult wind conditions.
So, we have a (single-line) kite and now we want to attach the camera to it. There are many ways do do it - in our humble KAP beginnings we taped a cheap mobile phone directly to the kite and did some terrible shots - some simple, some more complicated. Stability is most desired, both for video and stills. The wind changes, the kite dances, the line slacks and snaps back: every jerking move can ruin the shot.
The simplest way is to attach a stick on the line with a (action) camera on the dangling end. The stick absorbs some of the more violent line movements and the camera generally just sways to and fro. A video shot this way is rather dizzying, but some stills can look great.
More complicated but absolutely worth the is so-called Picavet rig. It consists of a platform with four pulleys (simple hooks do the trick) to which the camera is attached; then a separate line is threaded through all the pulleys in an ingenious way. Both ends are then attached to the kite line some (cca. 1 m) distance apart. The result is that the platform stays horizontal no matter what angle the kite line assumes (so the camera angle is constant), the only free movement is perpendicular to the kite line (that can be damped with a sail-like piece of fabric).
Picavet rig gives the camera much needed stability and constant angle-of-sight. As a platform, it can handle more than just a camera: you can play with electronics and remote controls, changing the pitch, yaw and roll of the camera, giving you total control in searching for the best shot live (we don't do that (yet), as we are a bit romantic; the excitement of anticipation is cool and we prefer to not know what we got until the camera is back on the ground - sometimes with dissappointing results, when someone (Janez!) forgets to start the camera timer).
A big enough kite can carry almost any camera there is. But don't go flying your 4.000€ EOS on your first (or 100th) KAP session: kites can - and do - crash, the trees love to eat them, water landings do happen and even in a controlled landing the camera ca hit the only rock on the meadow.
An action camera is light so it can be carried up on a smaller kite or in lighter winds; 4k videos can look superb if the wind is fairly constant, and stills are of reasonable quality. Field distortion and enormous FOV are the biggest drawbacks.
Compact camera is a great way to do KAP. It is flexible, versatile and light. Photo quality is well above action cam's. Easy to opreate; even full auto mode usually yields great results. A continuous shooting mode is essential (some cameras don't have that option, so beware, and you can upload CHDK software on some Canon compacts that does the trick) - we set it to shoot every 30 or 40 seconds, giving you around 50 to 60 shots per hour of flight.
MILCs and DSLRs are very heavy and expensive. A good, lower-price MILC can give your photos that je ne sais quoi that makes them stand out and mesmerise viewers. Full-body DSLR with a good lens does miracles. But, while they do amazing pictures, they are very heavy and expensive. This is top-end, ultimate KAP: you need a very big kite, a constant moderate wind and a lot of experience. Because, those cameras are heavy and expensive. Not to mention that they are very heavy and expensive!
That said, we use three cameras: a Denver ACT 5020TWC action camera (the coolest gift, thanks again @dronedisaster!), an old and trusty Canon Powershot A810 compact (with CHDK software), and a Nikon 1 J1 MILC.
So - build a kite, get a camera and start flying: the world is amazing, viewing it from the air even more!
MILLIE - FRENCH MILITARY KITE
The name stems from a mixed box/diamond design used in World War ! for lifting aerials and even human observers. This is a strong beast of a kite, with enormous pull, extremely steady flight even in very low wind conditions. Its very steep flying angle enables kite aerial photography of targets when it is not possible to get enough distance to. A versatile but for its pull a very demanding kite.
One more thing: KAP kites are single-line. Stunt kites - with two or more lines and great control - are too wild (but, maybe, you can do a cool video - if the camera doesn't corrupt the stability of the kite too much).