Kite height restriction in UK, away from airports, is 60m without CAA Permission
Aerial photographs taken from both planes and satellites are readily available on the internet (eg 1 2). The National Mapping Programme of English Heritage is an excellent example of how analysis of existing military aerial photography can cost-effectively, and substantially, increase the number of recorded sites.
The limitation of using existing images is that they are taken at a given point in time, which may not be the most appropriate for any given site. For example, you may want to bring out surface features by taking shots when the sun is casting strong shadows (ie when the sun is bright and low in the sky). Features on some archaeological sites may be highly dependent on the direction and angle of view, thus requiring numerous photos to be taken. On some sites, you many want to take photos when the soil is particularly dry, so that sub-surface features can be delineated by changes in the colour of vegetation or when there has been a fall of snow.
Ideally, to maximise the information from a site, comprehensive, high resolution aerial photography (usually from less than 60 metres and often much lower), in at least the visible part of the spectrum, should also be undertaken prior to planning any excavations. Such techniques can no longer be excluded on the basis of cost or difficulty and should be available to all archaeologists in the field. Near infra-red photography should be considered a routine procedure regardless of platform. On some sites, details, which are only visible in the near infra-red, would start to be lost once excavation began and it is clear that the failure to record such information would be bad practice. The cost of thermal imaging is slowly coming down.
Photographs should be taken at the most appropriate time of day/season/year for your application. If expense is not a problem, and there are no flight restrictions in operation for the intended area, this can be done by hiring either a helicopter or plane. You can take your own photos or you can commission your own survey. However, a cheaper alternative is to use model aircraft / UAV (1 2 3 ). Although cheaper, this approach may require some skill, depending on the aircraft of choice, and your equipment is always at risk of damage. However, with off-the-shelf systems and cheap digital cameras, this is certainly a viable option and there are some very cost effective gyro stabilization (2) solutions for the more serious photographers.
A camera-on-a-stick ( 1 2 3) approach is also possible and it has the advantage of not being as dependent on the weather conditions, but height is limited. Simple, portable poles should be part of the personal photographic kit of any field archaeologist.
Birds have been used for aerial photography for over 100 years.
Balloons are a stable choice (1
but they require relatively calm conditions. Helium balloons
work well, but they are not necessarily the cheapest
option. Hot air balloons appeal as a possible photographic
platform as they are both cheap to buy/make and to fly, but they
are limited to very specific and infrequent (here in Scotland!)
An effective compromise between a helium balloon and a kite is a Helikite.
The Aerial Archaeology Research Group is the specialist organisation for archaeological work but The Remote Sensing and Photogrammetry Society has archaeology , UAV and other special interest groups too.
The first kite we used was a Rokkaku design (Apperley) with one 5 foot vertical strut and two 4 foot horizontal struts 3 feet apart (= 16 square feet), using the camera's time-release setting to take a photo 10 seconds after launching.
After only a couple of flights, it became obvious that kite aerial photography (KAP) was the most appropriate method for our needs.