Figure 11 details the differences between the
ALS DSMs
and the camera
DSMs
. Figure 11a and 11b illustrates the order
in which the images were captured. Green represents lower
elevation areas, based on the
ALS DSM
data, and red represents
higher elevation areas. Yellow represents areas where the
DSM
did not significantly change. Figure 11 shows how the
banking earthworks progressed over time. Examination of
the changes in the earthworks, using the difference images,
demonstrated that the maximum
DSM
differences changed
according to the order in which the images were captured.
The maximum height in earthworks was 2.723 m for the S7
camera and 2.952 m for the
NX
device.
Summary
In this study, we tested a Samsung Galaxy S7 (smartphone)
and Samsung Galaxy
NX
(smart camera) with respect to the ac-
curacy of
UAV
photogrammetry.
We performed error analysis based on:
GPS
, orthophoto-
graphic,
DSM
, and volumetric error data. The
NX
showed an
RMSE
of 0.015 m for the
GPS
data, representing twofold higher
accuracy than the S7; similar error was seen between these
devices in the orthophoto area analysis. Comparing the
NX
to
the S7 on orthoimage and
DSM
, accuracy was higher compared
with the ground measurement (
TLS
,
GNSS
).
The uncertainty in the
DSM
data associated with the S7
with the rolling-shutter setting activated was almost the
same as that for the
NX
, especially with changing topography.
Especially in a sloped plane, the difference between the S7
image-based
DSM
with
RS
correction and the
TLS DSM
was
smaller than for the S7 without
RS
correction. Volumetric error
of 4.9% for the S7 and 3.1% for the
NX
does not meet legal re-
quirements for public surveying in some countries; more pre-
cise measurements will be required to meet work standards.
UAVs
may have many data acquisition and measurement
applications in civil engineering (Siebert and Teizer 2014), and
may fill an important niche in monitoring medium-scale stock-
piles (Hugenholtz
et al.
2015).
DSMs
were used to estimate earth-
works and confirm that
UAV
photogrammetry is suitable for use
on construction sites. These observations on
UAV
photogram-
metry offer useful guidelines for researchers and professionals
seeking to adapt
UAV
technology to their
Acknowledgments
This work was supported by a Research Grant of Pukyong
National University (2017 year).
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