Hyperspatial Imagery in Riverine Environments - Fluvial Remote Sensing for Science and Management - page 164

sometimes by timed release. These systems are primarily
used in stationary mode but they can be mobile at the
local scale. Most often these tethered devices are small
and work at relatively low altitudes ( < 350 m) to focus on
study areas if less than 10 ha. However, potential users
should check local airspace regulations since some avi-
ation authorities prohibit high altitude kite flying. For
example, in the UK, airspace regulations allow all teth-
ered devices to operate freely at altitudes up to 60 metres.
Any operations above this altitude require special per-
mission (Chubey et al., 2006). The almost toy-like nature
and raw materials involved mean that in principle these
devices can often be produced relatively cost-effectively
making use of light, low-cost cameras. The examples in
Table 8.1 show typical performance parameters for this
platform type. We can see that blimps and kites have been
used in applications ranging from topography mapping
to vegetation dynamics. When flying at low altitudes,
resolutions are in the hyperspatial range. However, we

can see that in this case, the areas covered are relatively
small and thus this platform is clearly not suited to large
scale sampling schemes. Interested readers are referred
to Aber et al. (2010) for a detailed treatment of small
format aerial photography using tethered platforms and
the flying platforms mentioned in the next section.

8.2.2.1 Unmanned Aerial Vehicles (UAVs) and
Ultra-Light Aerial Vehicles (ULAV)

In recent years, small aircraft, both unmanned (UAVs)
and manned (ULAVs), have begun to offer very interest-
ing alternatives to traditional platforms (e.g. Figure 8.3).
Unmanned Aerial Vehicles (UAVs), synonymously called
Unmanned Aerial Systems (UAS), provide a low-cost
opportunity to deliver hyperspatial imagery with a rapid
deployment time that allows the user to collect imagery
at monthly, weekly or even daily timescales. In con-
trast with tethered systems, they are most often used to

(a)
(c)

(b)
(d)

Figure 8.3 Examples of recently developed platforms.