Geography Reference
In-Depth Information
always be purchased. This is typically in excess of 20 km
2
which therefore places the minimum cost of a single, high
resolution, satellite image in the vicinity of 2000 US$.
In the case of airborne imagery, costs are also quite
variable. Dugdale et al. (2010) cite a cost of £150/km
(approximately 250 US$/km) for the acquisition of 3 cm
airborne imagery. This would however be in addition to
an initial mobilisation cost required to get the aircraft to
the mission locality. Typically, in the case of small rivers
with lengths below 100 km and widths below 100m,
surveys of full river lengths in order to acquire sub-
decimetric resolution colour imagery will probably cost
10 000 to 25 000 US$. However, many national agencies
maintain image archives for their territories. These are
generally of a much lower resolution, typically 25-50 cm.
However, their cost is much lower. Government agencies,
particularly in the US, will often provide these free of
charge. Even when not freely available, the cost is roughly
10% of the cost of a new survey. Small UAS are generally
affordable for most organisations. Depending on the size,
level of automation and imaging equipment of the craft
in question, costs can range from roughly 5000 US$ to
30 000 US$. These make them affordable options for 'do-
it-yourself' remote sensors. However, prospective UAS
pilots should take careful notice of national airspace
regulations. Airspace regulations in most western nations
now have specific regulations pertaining to UAS. The
spirit of most UAS airspace usage regulations is that
small, light weight, UAS operated in non-urban areas, at
low altitudes (below 400 ft or 120m) and within line of
sight of the pilot are allowed. This situation is generally
suitable to most river applications thus making UAS a
good option for river study and management in the US
and Europe. However, we strongly encourage readers
to consult specific regulatory agencies before purchasing
a UAS since regulations will vary across the globe and
may change rather rapidly. Furthermore, many regions
of the world do not allow any type of UAS operations.
For example, in India, airborne photography, both from
UAS and full aircraft, is strictly reserved to military uses.
Readers considering airborne photography of any kind
should therefore always check the regulatory framework
for their intended field site.
discussed in later chapters of this volume, river scientists
now have a wide range of remote sensing and image
based methods capable of quantifying the biotic and abi-
otic aspects of river environments. This progress has been
reflected in academic publications and here we focus on
a bibliometric survey in order to analyse the evolution
of Fluvial Remote Sensing (FRS). The ISI Web of Sci-
ence (WOS) database was used to provide a summary in
international peer-reviewed scientific journals and con-
ferences. Different searches were carried out based on
a set of technical key-words, such as 'Remote sensing',
'imagery/image', 'photogrammetry/photography', 'video'
combined with specific thematic key-words describing
our geographical objects such as 'river', ' stream', 'fluvial
channel', 'fluvial geomorphology', 'floodplain' and 'ripar-
ian'. We decided to reject the term 'river basin', which we
foundwas used for catchment or regional scale hydrology,
an observation in itself. We also rejected the terms 'video
stream' and 'image stream' which are used purely for
video technologies. The term 'channel' must also be used
with caution since it can be used in the purely technical
sense of a radiometric channel or video channel. From
this request,
1
224 references are specifically related to our
topic. Of the 224 references, 200 have an abstract. In a
second search phase, we introduced the terms 'manage-
ment', 'restoration', 'maintenance', but also 'planning'.
We did the second request
2
on the title for these addi-
tional keywords, the others being searched in the topics
to reassemble more papers 12 only were then identified.
As a first order analysis, if we consider the pace of
publications, we find that 1 to 3 papers were published
every year between 1976 and 1996, 7 to 9 papers per year
were published between 1997 and 2001, increasing to 11
to 14 per year from 2001 to 2006 and finally surpassing 30
per year since then with a maximum of 37 in 2010. This
increase in the number and pace of publications is in itself
a good indicator of the accelerating pace of progress in
this sub-discipline of remote sensing. In order to pursue
1
Exact request done in May 2011 : Title
(Remote sensing
OR image OR imagery OR photogr* OR video) AND Title
=
=
(river* OR stream OR streams OR fluvial channel* OR fluvial
geomorphology OR floodplain OR riparian) NOT Title
(basin*
OR catchment OR watershed OR ''video stream*'' OR ''image
stream'')
=
333 References listed but only 224 were really in the
scope of the discipline.
2
Exact request done in August 2011 : Title
=
1.3 Evolution of published work
in Fluvial Remote Sensing
(Remote sensing OR
imagery OR image OR photogr* OR video) and Topics
=
=
(river
The past decade has clearly seen remarkable contributions
to methodological aspects of fluvial remote sensing. As
OR streamOR fluvial) and Topics
(management OR restoration
OR maintenance OR planning OR conservation).
=
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