Geography Reference
In-Depth Information
D
50
30
Local grain size
estimation
(m)
20
10
0
0.2
−
60
−
40
−
20
0
20
40
0.15
D
16
30
0.1
20
0.05
10
0.0375
0
0.025
−
60
−
40
−
20
0
20
40
D
84
0.0125
30
0
20
10
0
−
60
−
40
−
20
0
20
40
Figure 14.3
Facies maps of the bar surface on the River South Tyne at Lambley produced from data clouds with point densities
averaging 10 000m
−
2
.
14.2.3 Thesub-barunit scale
gravel-bed channel, towards the tail of the outwash fan.
The channel was fed primarily by melt-water originating
from Glacier du Mont Mine, with the melt-water dis-
charge regime displaying a strong diurnal signal during
summer months. A LMS Z-210™ laser scanner manu-
factured by Riegl Instruments was used to collect a series
of independent datasets recording range, height, surface
colour and reflectivity. The instrument works on the
principle of 'time of flight' measurement using a pulsed
eye-safe infrared laser source (0
Many of the early-generation terrestrial laser scanners
were cumbersome, hence they were not usable in many
field situations beyond localised sediment studies at the
metre scale. More portable field scanners have been devel-
oped in the last decade thus offering (i) greater range (now
over 2 km (ii) increased rapidity of data collection asso-
ciated with an improvement in the angular resolution
of instruments (down to
0.001 degrees) and (iii)
improved ranging accuracy (of the order of a few mil-
limetres). An early study using this more portable field
scanning technology was conducted byMilan et al. (2007)
on the proglacial outwash fan of Glacier du Mont Mine
and Ferpecle situated in theValais regionof the Swiss Alps.
Survey work concentrated on a 5881m
2
reach of braided
+
/
−
mwavelength) emit-
ted in precisely defined angular directions controlled by a
spinning mirror arrangement. A sensor records the time
taken for light to be reflected from the incident surface.
Angular measurements are recorded to an accuracy of
0
·
9
μ
036
◦
in the vertical and 0
018
◦
in the horizontal.
·
·
·
Range error is 0
025 m to a radial distance of 350m
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