digital elevation model generated by unmanned aerial vehicle to
TRANSCRIPT
Proceedings of the 3rd Applied Science for Technology Innovation, ASTECHNOVA 2014
International Energy Conference
Yogyakarta, Indonesia, 13-14 August 2014
Digital Elevation Model Generated by Unmanned Aerial Vehicle to Determine Available Head Assessment for Micro Hydro Power Plant in
Merawu River, Banjarnegara Distric, Central Java
Aris Sunantyo
Department of Geodetic Engineering, Faculty of Engineering,Universitas Gajah Mada, Jl. Grafika
No. 2 Yogyakarta, Indonesia 55281
Suprapto Siswosukarto, Bambang Yulistiyanto Department of Civil and Environment Engineering, Faculty of Engineering,
UniversitasGadjahMada, Jl. Grafika No. 2 Yogyakarta, Indonesia 55281
Prajitno
Department of Mechanical Engineering, Faculty of Engineering, UniversitasGadjahMada, Jl.
Grafika No. 2 Yogyakarta, Indonesia 55281
ABSTRACT
Indonesia is one of the developing countries which hence needs huge amount of electrical energy
supply. Energy can be generated by renewable resources and un-renewable resources. Electricity is one of
the most important aspects in energy which can be generated by oil, gas, coal is a non renewable energy,
while the water, geothermal, solar, wind, bio fuels are renewable energy sources. Renewable energy is
the clean and environmental friendly energy source. Potential sources of renewable energy in Indonesia
are very redundant in solar energy, hydropower, geothermal power, wind power, and bio fuels.
Hydropower or water power is power derived from the energy of falling water and running water.
Hydropower is hydroelectric power, which is electricity produced by water. Micro-hydro power plant is
part of hydropower which a friendly structure to the environment, because it does not produce exhaust
gases or other waste, and does not damage the river ecosystem.
Power of electricity can be generated by energy of falling water and running water as micro-hydro
power plant. One of parameters of electricity power depends on available head. To map the research, it is
very important to establish Ground Control Points (GCP) for vertical and horizontal positioning in
carrying out aerial mapping with UAV technology. The vertical positioning of GCP uses orthometric
height which is referred to the height system in Sermo dam height system. The GCP has been established and computed to be 20 units. The result of research is orthophoto
mosaic, Digital Terrain Model (DTM), orthophoto mosaic with contour line, DTM with contour line, and
contour map in Merawu River, Banjarnegara district which is very hilly topography. Mapping with UAV
at this research area is very powerful tool and s very helpful in to determining an available head to design
inlet and outlet.
KEYWORDS: UAV, GCP, power, orthometric height, micro-hydro power plant, orthophoto mosaic,
contour line, and available head.
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1 INTRODUCTION
Water and energy are essential elements and are playing important roles in life. Energy is a basic
need of human being. Energy has an important role in our life to support economic activity. The
development of energy systems has been the backbone of global economic growth since the industrial
revolution in the mid-19th century. Indonesia is one of the developing countries which hence needs huge
amount of electrical energy supply. Energy consumption in Indonesia includes the household sector,
industry, transport, trade/commercial and public interests. Energy consumption can be divided into two
kinds namely electric and not electric energy consumptions. The electrical energy are needed for
household electricity demand (for lighting, cooking, refrigeration room, and various other household
activities) and for industry, commercial and public interests. Energy can be generated by renewable
resources and un-renewable resources. Electricity is one of the most important aspects in energy and also
the characteristic of the development. Electrical energy can be generated by oil, gas, coal is a non
renewable energy, while the water, geothermal, solar, wind, bio fuels (BBN= Bahan Bakar Nabati) are
renewable energy sources. Renewable energy is the clean and environmental friendly energy source. It
can be generated by the principle of sustainable development. It can be renewed, and the best thing about
them is they will not reduce any amount of energy resources they use for generating electricity. The
renewable energy resources will be the suitable answer, they fulfil many basic goals of sustainable
development, and they also will give less impact to the environment. The use of renewable energy is
basically utilizing the local potential of Indonesia. The utilization of renewable energy will be viable in
the economic point of view, as they can be protection against the global fossil fuel price fluctuations. The
use of renewable energy is reducing the dependency to fossil fuel, and is also reducing the dependency to
the other countries which are the oil exporter. The utilization of local potential will be able to give
opportunities for local people to get involved in the project development, creating more jobs, and improve
their living standards. Potential sources of renewable energy in Indonesia are very redundant in solar
energy, hydropower, geothermal power, wind power, and bio fuels. This strategy currently dominates the
development of a future energy system that stresses the use of fossil fuels. On the other hand,
environmental awareness, sustainable development and conventional resources depletion are now forcing
governments to review their energy strategies. Further, fossil fuel dependency has rapidly diminished
national oil reserves. In some developing countries, as well as Indonesia, development activities are
concentrated in cities or areas with facilities that support it. While in rural areas, development is hindered
by the lack of infrastructure and its facilities. To improve the quality of life and economic growth in rural
communities, the energy has a major role. Communities without a centralized electricity supply are more
dependent on the natural resource base for fuel for cooking, lighting and heating (Viljoen, 1992). In rural
areas increased use of wood for fuel contributes to deforestation, degradation of woodlands and changes
in biodiversity and species competition (Griffin et al., 1993). Electricity can be generated by on grid and
off grid. Availability of electricity in rural areas as a form of energy especially in off grid electricity will
be able to drive an increased productivity and new economic activity, improve education and health
facilities, and increased new jobs.
2 MICRO-HYDRO POWER PLANT
Hydropower or water power is power derived from the energy of falling water and running water
which electricity is produced by water (http://www.yourdictionary.com/hydropower). Micro-hydro power
plant is part of hydropower which a friendly structure to the environment, because it does not produce
exhaust gases or other waste, and does not damage the river ecosystem. Hydro power is one possible
method of generating electric power close to the potential consumers, thereby cutting out expensive
reticulation costs in widely spread rural areas. For sustainable electricity generation there must be stream
flows of sufficient flow rates down significant slopes. Hydroelectricity is the term referring to electricity
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generated by hydropower; the production of electrical power through the use of the gravitational force of
falling or flowing water (http://en.wikipedia.org/wiki/Hydroelectricity). Hydro power is being considered
as one of the options for generating power for rural communities, as it is less damaging environmentally
(http://en.wikipedia.org/wiki/Hydropower). Hydro power is sustainable in that water is a renewable
resource, and there are no emissions or effluents associated with hydro power generation. Micro-hydro is
the small scale harnessing of energy from falling water, generating typically less than 100 KW. The
advantage of small hydro power plants is their cost effectiveness and reliability of providing clean
electricity. Micro hydro power plant is a friendly structure to the environment, because it does not
produce exhaust gases or other waste, and does not damage the river ecosystem. It reduces the use of
fossil fuels for lighting and household activities such as cooking. Usually, Micro-Hydroelectric Power, or
Micro-Hydro, are used in the rural electrification and does not necessarily supply electricity to the
national grid. Hydroelectric energy advantages are (http://www.greenworldinvestor.com/2011/04/04/
hydroelectric-energy-advantages-and-disadvantages/): 1). No fuel cost; 2). Low operating costs and little
maintenance; 3). Low electricity cost; 4). No greenhouse gas emissions/air pollution; 5). Energy storage;
6). Small size possible; 7). Reliability; 8). High load factor; and 9). Long life. Hydroelectric energy
disadvantages such are: 1) Environmental, dislocation and tribal rights; 2) Wildlife and fishes get
affected; 3) Earthquake vulnerability; 4) Siltation; 5) Cannot be built anywhere; and 6) Long gestation
time.
Power is a function of the hydraulic head and rate of fluid flow. The head is the energy per unit
weight (or unit mass) of water. The static head is proportional to the difference in height through which
the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an
amount of work equal to its weight times the head. The power available from falling water can be
calculated from the flow rate and density of water, the height of fall, and the local acceleration due to
gravity. Micro-hydro schemes generally follow the layout shown in the following Figure 1.
Figure 1: General lay out of Micro-hydro schemes
The power available at a hydropower station will always be proportional to the product of the
available head and the volume flow rate of the site (Wiranto, 1997):
P = g Q (hfb - ht ) (1)
where
P is Power (in Watts),
η is the dimensionless efficiency of the turbine,
Q is volumetric flow rate (m3/s),
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ρ is density of water (kg/m), and
(hfb - ht ) is available head (m) (2)
Here available head is computed between inlet as intake weir and outlet as power house (see Figure
1). Operators of hydroelectric plants will compare the total electrical energy produced with the theoretical
potential energy of the water passing through the turbine to calculate efficiency. Concerning with Eq. (2),
available head means the orthometric height difference between inlet and outlet. Orthometric height is
the length of the plumb-line segment between earth surface to geoid reference at geoid normal line
(Moritz, 1966). Hydroelectricity is the most widely used form of renewable energy (Cranenbroeck, 2011).
Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably
lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants.
With its mostly hilly terrains and high precipitations distributed over a large part of the year, Indonesia is
blessed with an abundant potential for small-scale hydropower development such in this research area
(Merawu river Banjarnegara district). In Banjarnegara district, there are a lot of rivers which go from the
hilly terrain and high precipitations especially in the north of Banjarnegara district. It means that this area
has a big opportunity to carry out micro hydro power plant.
3 UNMANNED AERIAL VEHICLES (UAV)
An available head is orthometric height difference (see equation 2). The available head can be
determined by terrestrial or aerial photogrammetric method. Photogrammetric is the art, science and
technology. It involves several processes of physical object or certain areas in order to acquire
information about feature on the earth surface (Wolf and Dewitt, 2004). In case of photogrammetric
method, there are normal format photo, small format photo and Unmanned Aerial Vehicle (UAV) format
photo. The UAV is an aircraft without a human pilot aboard. Its flight is controlled either autonomously
by onboard computers or by the remote control of a pilot on the ground or in another vehicle. It means
that the UAV systems are remotely-controlled aircrafts. A microcomputer makes the autonomous
navigation without much manual involvement of a pilot possible. (http://en.wikipedia.org/wiki/
Unmanned_aerial_vehicle). The UAV or Remotely Piloted Vehicle mapping acitivities is used to deter-
mine geospatial data (positioning, coverage area, and dimension). The UAV carry several sensors such as
camera, GNSS receiver, communication, intelligence, surveillance, reconnaissance etc. The UAV ima-
gery is typically collected within a couple of hours, with a high number of images at very high
resolutions. The UAVs are notorious for poor camera quality compared to traditional large format
systems. Another important issue is the generation of precise orientation data (position & attitude of
sensor), often from rough GPS estimates only. Acquisition of high resolution images by UAV has certain
advantages over piloted aircraft missions, including lower cost, improved safety, flexibility in mission
planning, and closer proximity to the target. The photogrammetric products of UAV technology are stereo
model in three dimensional (3D), contour lines, Digital Elevation Model and digital orthophoto. The
UAV system can be used for large scale mapping and other diversified applications especially for small
area which has limited budget and time (Tahar el al, 2011). The quality of DEM and digital orthophoto
depends on the accuracy of Ground Control Point (GCP). If the quality of GCP is excellent, therefore the
result of DEM and digital orthophoto can be anticipated accurate too. The reasons of UAV for low
altitude photogrammetric mapping are: 1) to perform very low altitude aerial photography at cloudy day,
2) to get full image of city building form different direction by complicated flying, 3) to supply a cheap
and easy system for engineering organization for high frequency needs of aerial photogrammetric
survey. Tahar and Ahmad (2011) successfully used a rotary wing UAV and aerial photogrammetric
technique for mapping simulated model to generate Digital terrain Model (DTM) and orthophoto.
Characteristic of micro UAV (μ) depends on mass less than 5 kg, range is less than 10 km, flight altitude
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is about 250 m and endurance is less than one hour (UVSIA, 2010). UAV data collection is possible
under cloudless condition. With this advantage, UAV has been focus in the mapping research and various
applications such as engineering, environmental, agricultural, monitoring hazardous area etc.
4 DIGITAL ELEVATION MODEL (DEM)
Definition of a Digital Terrain Model (DTM) is information about the location of objects. The
DEM is a digital model or 3D representation of a terrain's surface. The DEM displays the relief of the
earth in digital format at regularly spaced horizontal intervals and is prerequisite for geometric,
radiometric and atmospheric corrections of optical and microwave instruments (Toutin, 2008). The DEM
is based on a higher number of points with X; Y and Z coordinates describing the bare soil. The DEM
may be arranged in a raster or a random form. Instead of the expression DEM also the term Digital Height
Model (DHM) is used. The DEM may be arranged in a raster or a random form. Instead of the expression
DEM also the term digital height model (DHM) is used. The DEM can be represented as a raster (a grid
of squares, also known as a height map when representing elevation) or as a vector-based Triangular
Irregular Network (TIN). The TIN of DEM dataset is also referred to as a primary (measured) DEM,
whereas the Raster DEM is referred to as a secondary (computed) DEM. The DEM could be acquired
through techniques such as photogrammetry, LIDAR, IFSAR, land surveying, etc (Li et al. 2005). The
DEM consists of terrain elevations for ground positions at regularly spaced horizontal intervals (Yu and
Ge, 2010). DEMs can be used, for example, in the generation of three-dimensional graphics displaying
terrain slope, aspect, and terrain profiles between selected points. Digital Elevation Models (DEMs) are
an important source of information in many geospatial applications where they are used in modelling,
visualization, correction of satellite imagery, etc. In all software and DEM generation technique, there is
always a need for post-processing the output DEM, to eliminate void, blunders and filling the mismatched
areas. Generally, manual, automatic and interactive techniques are used to edit the output DEM (Toutin,
2002). In order to generate DEM, the earth model and datum were set to UTM (zone 49N) and WGS84
respectively. The output DEM is an accumulation of different automatic and manual processing steps,
such as collecting and importing GCPs/Tie points, geometrical processing, image matching and editing
the final DEM. Therefore, the accuracy of each step affects the ultimate accuracy of DEM. DEMs have
become an important source of topographical data for many scientific and engineering uses, such as
hydrological and geological studies, infrastructure planning and environmental applications. Several
advantages of UAV are fast data aquisistion, precise result, low cost, medium scale. This advantage will
be very useful for sevaral application such as cooridore mapping of route and river, agricultural
production, forest monitoring, terrain modeling, mining etc. In a UAV survey, the aircraft operates
autonomously, acquiring photography according to a predetermined flight plan. Planning is carried out
using proprietary software, which uses the site boundary, desired flying height, and desired overlap
between photos as inputs. The program then produces a flight plan, which includes GPS waypoints, as
well as the location of projected photo centres. This flight plan is uploaded to the onboard autopilot,
which then guides the aircraft through the flight. Except for takeoff, the entire flight is autonomous, with
the operator only intervening in unforeseen circumstances. Landings are performed by an automatic
parachute deployment. Following the flight, the photographs, GPS flight log and data are downloaded for
further processing. Processing is carried out in house using photogrammetric software. The logfile is used
to provide initial estimates of camera positions and orientations for each photo. Survey grade ground
control points are used to refine the estimate, with final adjusted camera positions and orientations being
produced using a rigorous block adjustment procedure. Once the acquisition geometry has been
successfully recreated, detailed 3-D elevation models can be created, typically with a grid spacing of one
metre. The digital elevation models are then used to produce a high-resolution orthophoto mosaic
covering the site with a spatial resolution of 10 centimetres or better.
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Banjarnegara district is one of some district in central Java provinces, Indonesia. This district is
hilly topography especially in the northern part of district so it is very good place to generate electricity
with Micro Hydro Power plant (MHP). This district is also is one of many rural areas in Indonesia. The
power available at a hydro power station will always be proportional to the product of the available head
and the volume flow rate of the site. In 2011 this district has more about 104 Hamlet which are in 47
villages and they have not been able to enjoy the electricity grid. It is caused due to geographical
conditions that are predominantly mountainous settlements tend to cluster small-group and inter-group
sufficiently far apart. These conditions are very difficult to make a settlement reached by the grid. This
district has many rivers that are now trying to further improve the utilization of small-scale hydropower.
In addition to its considerable potential as well as for the MHP proved able to reach out to remote are as
in the district. In the current circumstances in order to meet the demand for electric power, it is
indispensable to optimize the utilization of electrical energy potential and also explore the sources of new
energy, especially renewable energy sources. One source of renewable energy development is now
activated for the district in which is the MHP Banjarnegara quite abundant streams and irrigation that can
be used as MHP. So the use of all energy sources until now not been able to meet the demand for
electricity in this district. It is also caused by conditions this district which is largely mountainous, so that
in some places very difficult to install the electrical grid. Concerning equation (2), one of parameter to
determine a power of micro hydro is available head. To generate available head, it can be carried out by
several methods such as terrestrial mapping and aerial mapping. Recently, Unmanned Aerial Vehicle
(UAV) technology is a new technology of aerial mapping technology which has been used widely in
several applications such as large scale mapping, agriculture and surveillance etc.
In this paper will be discussed that a precise DEM generated by using UAV technology. This
technology will be very potential in determining available head for computing a power of micro hydro
research. This research will be conducted in Merawu river, Banjarnegara district, central Java Province.
5 RESEARCH METHOD
In carrying out of this research, it is divided into several steps. The steps are preliminary study,
field work, data processing, results and analysis. Preliminary study covered literature review,
determination of scope and objective and design of Ground Control Point (GCP) using Google Map. Field
work consists of site visit location of research, establishment of GCP, vertical horizontal and horizontal
positioning of GCP and data acquisition of images with UAV. The GCP was made by PVC, sand and
cement (dimension 1 x 3 meter) and deployed from north to south to cover at least all of research area.
The GCP number is 20 units and one GCP of BMBBWSSO as an orthometric height reference which is
managed by Sempor dam office. Determination of orthometric height the 20 GCP units was carried out
by tachymetry method with Total Station instrument (see Fig. 2(a)). The horizontal positioning system of
every GCP was done by relative static method with GNSS receivers (see Figure 2(b)), where SPECTRA
commercial software for GNSS data processing was used. The final product of horizontal positioning
system is UTM coordinates system. The UAV was carried out to produce aerial images at the research
area (see Figure 2 (c)).
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(a) (b) (c)
Figure 2: Data acquisition at field work section where (a) is vertical positioning at GCP, (b) is
horizontal positioning at GCP (yellow colour as UAV Premark) and (c) is aerial with UAV
Before UAV photogrammetric work is carried out, flight planning is the most important task that
need be considered which contributes to the quality of data acquisition Teizer and Siebert, 2014). Flight
planning involves calculation of study area, number of strips required, pixel size, photo scale, flying
height and percentage of end lap and side lap. In general, aerial photograph should be overlapped at least
60% percent and side at least 30%. The aerial mapping uses UAV will result 3 Dimensional
representation terrain's surface. Then data processing of UAV has been divided into two sections. The
two sections are interior orientation, exterior orientation and block triangulation for mobile and fixed
platform.
(a) (b)
Figure 3: (a). The GCP Distribution which is generated by UAV and (b). The UAV data acquisition
in Merawu River, Banjarnegara Distric, Central Java Province
The flight for UAV data acquisition is west to east as dots symbol (see Figure 3 (a)), and depends on the
topographical surface flight and during the UAV data acquisition is shown at Figure 3 (b).
6 RESULT AND DISCUSSION
Result of this research is orthophoto mosaic, Digital Terrain Model (DTM), orthophoto mosaic
with contour line, DTM with contour line, and contour map. After vertical and horizontal positioning all
GCP, then the is very essential not only for orientation to carry out photo stereo model, aerial control
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orthophoto mosaic but also to be used as controlling of GCP between terrestrial data processing and aerial
processing.
(a) (b)
Figure 4: Results of UAV mapping at Merawu River, Banjarnegara District, Central Java Province.
An available head is one of very important parameters to compute power (see equation 2).
Concerning with Figure 4 (b) an available head is possible to be determined using interpolation of
contours line where inlet and outlet are designed already. Inlet means a high place which is used to seize
water flow and outlet means a a place which is used to trigger of energy using falling water to rotate
turbine. In analysis section, the differences between results from fixed and mobile platform are compared.
Fixed point is an orthometric height as a computation result using Total Station and mobile platform is an
orthometric height as a computation result using aerial triangulation of UAV. The difference between
results from fixed and mobile platform is shown at Table 1.
Table 1: The difference between results from fixed and mobile platform
Number Name of Bench
Mark
Value of error comparison between
fixed and mobile points (m)
1 BM02 0,059
2 BM04 0,176
3 BM06 – 0,042
4 BM11 –0,091
5 BM14 0,038
6 BM18 –0,060
Table 1 shows that the error comparison between fixed and mobile points has range about 176 mm
to –91 mm where numerical values of 176 mm happens at BM04 and –91 mm happens at BM11.
Discussion among team of authors especially from hydrological point of view, these numerical values is
still good to be able to determine power.
7 CONCLUSION
1. An aerial mapping with UAV at Merawu river, Banjarnegara district, central Java province
products orthophoto mosaic, Digital Terrain Model (DTM), orthophoto mosaic with contour
line, DTM with contour line, and contour map.
2. An available head using contour lines in orthometric height system is very useful to design
inlet and outlet as one of power parameters in micro-hydro power plant.
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3. The research area is very hilly topography so it is very good place to design micro-hydro power
plant especially in off grid electricity.
8 ACKNOWLEDGEMENTS
All of authors are really thank to Research and Civilian Services Gadjah Mada University who give
financial support to carry out the research. All of authors are also thank to Energy and Human Resources,
Banjarnegara District who very kind support to cooperate in giving permission of field data aqusition and
local labors people to carry out this research completely.
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