5.2 Design of the Measurement System
61
5.2 Design of the Measurement System
5.2.1 A Movable Tent for Field Study
The experimental house built in the field was adapted from a large bivouac tent and
could be assembled. Generally, the tourism tents available on the market could not
be used directly on steep slopes. Furthermore, the tents could not resist strong winds
due to their slender steel poles. In this study, besides the iron wires provided by the
manufacturer of the tent, many mooring ropes were used to fix the tent, together with
a high-strength concrete pole based on a large pier on the downhill side, as shown in
Fig. 5.2a, b. All of the measures made the tent very steady.
In addition, four sturdy columns were installed in the lower reaches of the slope.
The tent poles at the lower-lying area were connected with the columns that had
several equidistant connecting holes along their height directions. When the camp
pole was fixed with the bolts in different connecting holes on the column, various
lengthening effects could be attained. The scheme to lengthen the tent poles with the
concrete columns completely solved the problem of the altitude difference on the
steep slope (Fig. 5.2a). If the site terrain was prepared, the tent could be built with a
surprising speed in 2–3 days.
5.2.2 Operating Principle of the MX-2010-G Topography
Meter
A structured-light 3D surface-measuring instrument, the MX-2010-G topography
meter, was designed and manufactured to observe the slope behavior under rainfall
simulation. In our experimental system, the topography meter’s setup consists of
the following conventional components: sight calibrator, laser source, camera, and
positioning device. Figure 5.3 shows a representative scheme for quantitative monitoring of gravity erosion with the MX-2010-G topography meter. The horizontal
stripe pattern with a 3.0 cm contour interval was generated by a laser source, and
the pattern was recorded by the camera with a sighting direction perpendicular to
the laser planes. A camera with a collimator was mounted on the bracket. The collimator could submit a line-shape beam parallel to the camera sightline. As the slope
deformed over time, the process would be recorded on video and then imported into
the computer to acquire a snapshot image at a particular time. Given an elevation for
every contour in ArcGIS, the 3D geometric shape of the target surface was digitally
reconstructed and then the slope parameters, including the volume, projected area,
and gradient distribution, could be determined. Thus, we could obtain the volume
of gravity erosion and many other erosion data by comparing the slope geometries
in the moments before and after the erosion incident. In this study, the topography
meter covered a monitoring range of 3.0 m × 2.0 m.
61
5.2 Design of the Measurement System
5.2.1 A Movable Tent for Field Study
The experimental house built in the field was adapted from a large bivouac tent and
could be assembled. Generally, the tourism tents available on the market could not
be used directly on steep slopes. Furthermore, the tents could not resist strong winds
due to their slender steel poles. In this study, besides the iron wires provided by the
manufacturer of the tent, many mooring ropes were used to fix the tent, together with
a high-strength concrete pole based on a large pier on the downhill side, as shown in
Fig. 5.2a, b. All of the measures made the tent very steady.
In addition, four sturdy columns were installed in the lower reaches of the slope.
The tent poles at the lower-lying area were connected with the columns that had
several equidistant connecting holes along their height directions. When the camp
pole was fixed with the bolts in different connecting holes on the column, various
lengthening effects could be attained. The scheme to lengthen the tent poles with the
concrete columns completely solved the problem of the altitude difference on the
steep slope (Fig. 5.2a). If the site terrain was prepared, the tent could be built with a
surprising speed in 2–3 days.
5.2.2 Operating Principle of the MX-2010-G Topography
Meter
A structured-light 3D surface-measuring instrument, the MX-2010-G topography
meter, was designed and manufactured to observe the slope behavior under rainfall
simulation. In our experimental system, the topography meter’s setup consists of
the following conventional components: sight calibrator, laser source, camera, and
positioning device. Figure 5.3 shows a representative scheme for quantitative monitoring of gravity erosion with the MX-2010-G topography meter. The horizontal
stripe pattern with a 3.0 cm contour interval was generated by a laser source, and
the pattern was recorded by the camera with a sighting direction perpendicular to
the laser planes. A camera with a collimator was mounted on the bracket. The collimator could submit a line-shape beam parallel to the camera sightline. As the slope
deformed over time, the process would be recorded on video and then imported into
the computer to acquire a snapshot image at a particular time. Given an elevation for
every contour in ArcGIS, the 3D geometric shape of the target surface was digitally
reconstructed and then the slope parameters, including the volume, projected area,
and gradient distribution, could be determined. Thus, we could obtain the volume
of gravity erosion and many other erosion data by comparing the slope geometries
in the moments before and after the erosion incident. In this study, the topography
meter covered a monitoring range of 3.0 m × 2.0 m.