Applications of Close-range Imagery in River Research - Fluvial Remote Sensing for Science and Management - page 333

Table 15.1 Specifications for three cameras developed for the hunting industry. Details were extracted from company websites,
August 2011.

Specifics Reconyx Hyperfire PC800 Trophy Cam Bushnell Moultry Game Spy M-100

Image
resolution

3.1 Megapixels 8.0 Megapixels 6.0 Megapixels

Camera Custom focal distance, telephoto

lens, custom motion detector
lens, custom colour

LCD Display LCD Display

Trigger mode
configuration

From 2 pictures per second to 2
pictures per minute; up to 1
hour delay between triggers
1/5 th

From 1 picture per second to 1
picture per hour; up to 1 hour
delay between triggers

Maximum 3 pictures per 15
seconds; up to 1 hour delay
between triggers

second trigger speed

Time lapse
configuration

Virtually any number of
seconds, minutes, or hours

From 1 picture per minute to 1
picture per hour.

From 1 picture per 5 seconds to
1 picture per minute.

Video Not available. From 1 seconds to 1 minute From 5 to 30 seconds

Battery 12 AA; battery life up to 40 000

pictures

12 AA; battery life up to 1 year 4 D-Cell

approximately 50 meters, the ground resolution of the
Hyperfire camera is 5 mm/pixel. This resolution might
be limiting for sophisticated grain size and DEM anal-
ysis. For an oblique photograph, resolution also varies
from the foreground to the background, similarly to
the ground video settings discussed in Chapter 16. The
camera uses 12 AA batteries allowing collection of up
to 40 000 pictures, depending on ambient temperature
(as this affects battery charge), acquisition frequency and
activation of the infrared flash. The Reconyx camera is
self focusing and it automatically determines exposure
time. This may lead to variable image quality, especially
where contrast is high in the field of view. Nevertheless,
the Reconyx camera can be successfully used to document
the chronology of events occurring at the scale of a river
reach for time periods varying from one day to one year.
Amongst other applications, these cameras have been
used by Buffin-Belanger and colleagues to document the
activation of abandoned river channels, the formation
and dislocation of river ice covers, the displacement of
large woody debris, daily changes in proglacial stream dis-
charge and morphology and erosion processes occurring
on river banks.

also obtained images from low-level cranes, extendable
masts, or tethered balloons. A common application of
ground-based vertical photography is the characterisation
of surface grain size and bed roughness (Table 15.2,
Figure 15.2), applications that are now being explored
using ground-LIDAR (see Chapter 14). Considerable
work has been published in this domain with the devel-
opment of software such as the digital gravelometer that
enables automatic grain-sizing from hand-held vertical
photography (Graham et al., 2005a, b). Following this
approach, Rollet (2007) collected 107 photographs of bed
surface sediments from every gravel bar along a 40 km
reach of the Ain River, France and identified two dis-
tinct reaches; an upstream reach with infrequent, coarse
gravel bars affected by dam starvation and a downstream
reach not yet affected, with much smaller particles. Addi-
tional applications of close-range vertical imagery of bed
sediments include characterisation of morphometry and
petrography (see details in section 4 of this chapter).
Oblique acquisition of close-range photos remains,
however, the most frequent scenario and, again, several
situations exist.
On the Waimakariri River, New Zealand, Hicks et al.
(2002) explored the possibility of using video cameras,
mounted 35 m above the river bed, to provide hourly
imagery of the study reach. This technique produced
an invaluable record of the river's morphodynamics
and highlighted the coherence of morphologic features.
This amount and quality of data, common in flume

15.2.2 Overviewofpossibleapplications

Close-range photographs can be acquired vertically or
obliquely. Vertical acquisitions can be achieved at head
height or from a tripod. To gain height and there-
fore capture larger ground areas, some researchers have