Monitoring
and observing the condition of natural resources and phenomenon becomes a major
concern in many countries. Fancy et al. (2009) believe that those
monitoring programs can help stakeholders to develop an understanding of status
and trends of the natural, hence it can be a basis for decision-making for the
long-term protection of natural resources such as coral reefs, deserts, arctic
tundra, prairie grasslands, caves, and tropical rainforests. One of the most effective tools to monitor
and observe natural condition is by using maps. Mapping of natural condition
has become a common strategy in a natural reserve design. Flather et al. (1997) comment that
maps can make planners and researchers in a strategic position to describe
natural patterns and to study the processes behind the pattern. It is
important, then, to understand what kinds of method and technology that can be
utilized to create maps. This essay will examine two different mapping
technologies, terrestrial survey and Unmanned Aerial Vehicle, in term of efficiency,
effectiveness, final maps products, costs and operating limitations then suggest
that an Unmanned Aerial Vehicle can be an effective tool in wide areas mapping.
The
most common method to survey and map an area is using conventional terrestrial
surveying. The terrestrial survey usually uses total station equipment and
prism reflectors to measure distance and angle from one point to other points
in earth surface. The terrestrial survey needs at least two persons to conduct
the survey, one person for operating the total station instrument and another
person for taking a prism target to the intended position (Lee et al. 2013). However, in
actual condition, conducting terrestrial survey can be more effective by four
persons or more. Terrestrial surveying is a famous mapping method for small and
narrow areas since it uses simple equipments and conducted by foot survey. Lee et al. (2013) also argue that
this method is also very adequate for monitoring natural phenomenon changes in
detail at a small area.
UAV
or Unmanned Aerial Vehicle or sometimes known as drone is an aerial robot that
piloted remotely (Colomina & Molina 2014, cited in ICAO
2011). Klemas (2015) says ‘UAVs are
powered aircraft operated remotely or autonomously with preprogrammed flight
planning’. This technology can be used to obtain high-resolution earth surface
images at a lower cost so it can increase operational flexibility and bigger
adaptability. As a final result, data that obtained from UAV can be created as
maps then can be a powerful tool to monitor and to observe environment
phenomenon.
Firstly,
efficiency is an important factor in surveying and mapping. UAV technologies are
more efficient than terrestrial surveying since this technology can minimize time
consumption and improve cost-effectiveness (Tapete et al. 2015, cited in Liu
& Yang, 2015). Koh & Wich (2012) have
proven with their drone equipment that used for rainforest mapping in Sumatra,
Indonesia that it can fly autonomously for a total flight time of 25 minutes
and can cover a distance of 15 km. In addition, UAV systems have better coverage of mapping than
terrestrial survey. For instance, in 2012, Zarco-Tejada et al. (2014) conducted research about the use of AUV for olive
orchards plants mapping in Alcolea,
Cordoba, Southern Spain. Using a UAV system that has approximately 63 km/hours
of ground speed and flight 200 m above land surface then the maps that
generated for one area can cover 92.58 ha and the map has an overlap 80 – 90 % between
each other. It means that in one time of flight,
this equipment can map and cover wider coverage areas than a terrestrial
survey. The coverage superiority and time saving are some evidence that UAV
system is an efficient technology for mapping.
On the other hand,
terrestrial survey method has lower time consume than UAV survey. A terrestrial
survey requires at least four persons to conduct the survey to get an optimal
field operation. Hill & Geosystems (2008) have
proven by conducting a topographic survey of a car park with 0.57 hectare using
terrestrial survey and total time consume was 135 minutes. Similarly, Lee et al. (2013) conducted a survey study in Gosapo
Beach, the west coast of Korea. This area is characterized by the macro-tidal
condition with a maximum tidal range over 6 m during the spring tidal period,
which means that during high tide, the survey operation cannot be done because
all of the coastal lines are covered by water. Lee has proven that using
terrestrial survey with four survey persons and the time efficiency is just 10
meters per minute. Koh & Wich (2012) also report in
his study of assessment and monitoring of Orang Utan populations in Sumatra,
Indonesia that using ground surveys can cost up to $250,000 for a two-year
survey cycle. It means that terrestrial survey is time-consuming, financially
expensive, and logistically challenging in remote areas. Due to this high cost,
surveys cannot be conducted regularly and as a result, governments and
researchers will lack appropriate data for analysis and monitoring of
population trends.
Secondly, a UAV system can cover of difficult
and dangerous areas effectively since it uses an unmanned vehicle that can fly
far from the operator so the operator itself can be placed in a safe location. These
remote areas are difficult to access and consequently, study and monitoring of
these areas are impossible to be done. ‘some remote tropical forests have never
been surveyed for biodiversity due to difficult and inaccessible terrain’ (Koh & Wich 2012, cited in Palace,
M. et al. 2008). UAVs also have been
proven as an effective tool to map a dangerous location. For example, UAVs have
replaced manned aircraft in studies of remote and dangerous areas, such as the
complex coastal topography and polar regions (Klemas 2015). Another example
in Japan in 2011 when earthquake and tsunami hit Fukushima Daiichi Nuclear
Power Plant on Japan’s eastern coast and released significant quantities of
radioactive material. After that incident, (Martin et al. 2016) conducted high-resolution
radiation mapping using a UAV system to remedy large contaminated region of
Japan surrounding the Fukushima Plant. The survey then successfully record and
map contamination at the meter scale and furthermore chooses some appropriate
remediation actions for the site. That action, of course, cannot be done by
foot-based surveying like terrestrial survey since it can be very dangerous for
human to enter the radiation contaminated areas. In the future, water
environment emergency monitoring method using UAV system is still explored and
will be developed (Liu et al. 2010).
Thirdly, UAV offers
variety products not only contour maps but also three-dimensional maps and
photographic maps, then these maps can be combined with other data using GIS software. Fedra & Feoli (1998) explain that a geographic information system
(GIS) consist of several software tools can be utilized to obtain, handle,
process and display geographical data. Papakonstantinou et al.
(2016) show in a survey that conducted in Eressos and
Neapolis coastline, Greece in 2015 that UAV system can be a powerful tool for
classification, generates 3D images and maps of coastal morphology, so it can
be used for analyzing changes in coastal monitoring such as erosion in coastal
zones. It then can be a powerful tool in urban and environmental
planning. Grecea et al. (2016) suggest that 3D
models of objects from UAV survey also can be combined with other data using a
web Geographic Information System (GIS) then this information system can be
accessed on-line by many stakeholders for many purposes. On the other hand,
terrestrial survey can only create limited products than UAV system since the
survey equipments are much simpler than UAV technology. In general, the data
processing steps are only downloading data from survey equipment, process the
data using simple software and creating two-dimensional contour maps (El et al. 2002).
Fourthly, another
thing that should be considered in choosing a mapping method is products and
operation cost. UAVs system consists of several high-technology equipments such
as unmanned aircraft, Global Navigation Satellite Systems (GNSS) such
as GPS and Inertial Navigation Systems (INS) which is used to keep the UAV
remains stable (Colomina & Molina 2014). Those
equipments are not cheap and need adequate money investment to get it. Klemas (2015) illustrates that
a cheap UAV system has a price over than $10,000 and the price depends on their
capability, stability, range and instrument payload. Neitzel & Klonowski (2012) also argue that
the cost of UAV survey can be approximately 100,000 euros which means that only
a small number of countries can spend their money easily for this kind of
survey. However, Koh & Wich (2012) from Department
of Environmental Systems Science, ETH Zurich, Switzerland have developed a low-cost
unmanned aerial vehicle for surveying and mapping forests and biodiversity with
total cost is just around $2,000. It means that in the future the low-cost UAV
will be developed further; hence it can encourage many countries to use this
technology. On the other hand, the price of one set of terrestrial survey
equipment is just around $5,000. As a result, this equipment is more affordable
than a UAV system and many companies and institutions have owned it.
Lastly,
operating a UAV equipment is not as simple as our imagination and there are
many challenges to operating it. Albaker & Rahim (2009) believe that the
ability to navigate in urban or unknown terrain is very important in a UAV
survey since there are many different types and sizes of obstacles that can
endanger the equipment. Although a UAV system has tools to be used in difficult
terrain, a good piloting skill of its operator is compulsory otherwise the
equipment can hit or drop in a remote area that can lead to the damage of the
equipment. In addition, Siebert
& Teizer (2014) note
that strong thermal winds can cause air turbulences for the UAV. Wind gusts of
more than 40 km/h can endanger to the UAV and the survey needs to be canceled.
They also suggest that high-populated areas need to be avoided in UAV survey
since there are many bystanders (pedestrians or other traffic) that can be
endangered. Other environmental hazards such as trees and building also should also
be avoided during the survey, the potential of collision to these obstructions
can endanger the equipment. Another factor that should be counted is equipment’s
power supply. Simic et al. (2015) investigate that
the electric power supply is another important limitation for UAV survey and it
can influence to its range and endurance. As increasing battery system size is
not a suitable solution due to its weight, so they conducted research to
investigate the possibility of using wireless energy transfer to UAV during the
survey via electrical power transmission. In contrast, a terrestrial survey can
be conducted much simpler than UAV survey. The terrestrial survey can be
conducted easier in areas with complex topographic terrain, many environmental
obstacles and high populated. The main obstacle of the terrestrial survey is
only the weather since the equipment is usually not water resistant so the
survey cannot be conducted during the rain.
In
conclusion, there are several methods and technologies that can be used to map areas
for monitoring and planning purposes. Two of those technologies that have been
used widely in many countries are conventional terrestrial surveying and
unmanned aerial vehicle. Each of these technologies has own strengths and
weaknesses. While terrestrial survey has a predominance to be used in small
areas, UAV offers benefits to map large and restricted areas also it can
produce a variety of attractive maps.
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