Rapid assessment of energy biomass resources using aerial photographs from unmanned aerial ...

35 Pages·2014·2.28 MB·English

by  Anna Lopatina

University of Eastern Finland

Luonnontieteiden ja
metsätieteiden tiedekunta
Faculty of Science and
Forestry

Rapid assessment of energy biomass resources using aerial photographs
from unmanned aerial vehicles

Anna Lopatina

MASTER’S THESIS IN CBU FORESTRY
AND ENVIRONMENTAL ENGINEERING

JOENSUU 2013

1
Content
1. Introduction ...................................................................................................................................... 5
1.1. Application of UAV for biomass inventory.................................................................................... 6
1.2. Utilization of common reed biomass for energy production ......................................................... 8
1.3. Utilization of forest biomass for energy production ................................................................... 11
1.4. Aims of the study ......................................................................................................................... 12
2. Data ................................................................................................................................................ 12
2.1. UAV data ..................................................................................................................................... 12
2.2. Field Measurements. ................................................................................................................... 17
3. Methods .......................................................................................................................................... 18
4. Results ............................................................................................................................................ 20
4.1. Three-dimensional landscape model ........................................................................................... 20
4.2. Biomass distribution within the landscape .................................................................................. 23
4.3. Common reed biomass ................................................................................................................ 24
4.4. Forest biomass ............................................................................................................................ 25
4.5. Accuracy of forest and reed biomass resources assessment based on data from unmanned
aerial vehicles ......................................................................................................................................... 26
4.6. Speed and efficiency of the UAV-based biomass assessment ...................................................... 29
5. Discussion ...................................................................................................................................... 30
6. References ...................................................................................................................................... 33

2
Lopatina, A. Rapid assessment of energy biomass resources using aerial photographs from
unmanned aerial vehicles. Master’s thesis in Forestry and Environmental Engineering, Finnish-
Russian Cross-Border University (CBU), Faculty of Science and Forestry, University of Eastern
Finland, 32 p.

ABSTRACT
The increasing need to reduce greenhouse gas emissions to slow down climate change requires
more effective and versatile methods for producing energy. In Finland forest biomass and
common reed are used for energy production. There are efforts to increase the utilisation of
renewable energy resources. The potential intensification of renewables utilisation may result in
changes to the landscape’s structure and functions. The objective of this study was to develop a
method for energy biomass mapping in landscapes using high resolution remote sensing data
from an unmanned aerial vehicle. It was possible to develop an accurate three-dimensional
model of the biomass distribution within the landscape. The error in height measurements of
common reed plants and forest trees was 0.044 m. The error in common reed biomass
measurements using the UAV data obtained was 0.096 m3.

Keywords: biomass, UAV, forest inventory, common reed, remote sensing, classification,
segmentation, photogrammetry.

3
Acknowledgements
The author expresses her deepest gratitude to her supervisor Prof. Lauri Sikanen, Faculty of
Forest Sciences, University of Eastern Finland. The work was carried out within the Järviruoko
project at the School of Forest Sciences.
Furthermore, the author expresses her special thanks to Alpo Hassinen for providing aerial
images from unmanned aerial vehicle. The author would like to thank everybody who has helped
with the realisation of this thesis project.
Joensuu, April 2013

Anna Lopatina, School of Forest Sciences.
University of Eastern Finland.
Joensuu, Finland.
Email: [email protected]

4
1. Introduction

Global energy use projections predict that biomass will be an important source of renewable
energy in the coming decades (Parry, 2007). The development and use of biomass resources for
bio products and bioenergy has become a critical priority in Europe. This is driven by growing
concerns about environmental impacts associated with the use of fossil fuels, national energy
security, the sustainability of natural resources, and the need to revitalise rural economies.
Biomass can derive from a number of different sources, including forests, agricultural crops,
various residue streams, and dedicated woody or herbaceous crops. There has been increasing
interest in developing dedicated woody crops grown on short rotations, primarily because of the
multiple environmental, rural development, and social benefits associated with their production
and use (Volk, 2004). Biomass currently provides about 10.5% of the global primary energy
supply (Ferrentino, 2007), although some is not being produced and used sustainably. Most
projections of global energy use predict that in the future biomass will be a more important
component of primary energy sources, and that woody crops will be the primary source of
biomass (Berndes and Broek, 2003).
The development of EU policies is targeted at a reduction of greenhouse gas emissions of at least
20% below the 1990 level; achieving 20% of EU energy consumption from renewable resources
and a 20% reduction in primary energy, meaning an improvement in energy efficiency
(European Union, 2009). The 20% minimum of total primary energy consumption in Finland is
already met by bioenergy. However, the National Action Plan for Renewable Energy Sources
(RES) aspires to a further increase in the use of biomass: stating that by 2010 the use of
bioenergy energy sources should be 30% higher than in 2001. The National Action Plan for
Renewable Energy Sources is a key objective in Finland’s energy policy. It was launched in
1999 and updated in 2002. The RES National commitments for the years 2015 and 2025 aim to
increase the share of bioenergy in electricity and heat production by 25% and 40% respectively.
The European Landscape Convention – also known as the Florence Convention – promotes the
protection, management and planning of European landscapes and organises European co-
operation on landscape issues. The convention was adopted on 20 October 2000 in Florence
(Italy) and came into force on 1 March 2004 (Council of Europe Treaty Series no. 176). It is
open for signature by member states of the Council of Europe and for accession by the European
Community and other European non-member states. It is the first international treaty to be
exclusively concerned with all dimensions of the European landscape (European Landscape
5
Convention, 2000). The development of new approaches to landscape planning is needed for
implementation in the European Landscape Convention (2000). Intensification of energy
extraction from renewables in the future will affect the structure and functions of the landscape.
Therefore the tools are needed for energy biomass and energy content assessment within the
landscapes.
In Finland there are two main sources of renewables that are used for heat energy production:
common reed and forest biomass. Very often both sources of renewable energy are used
together.
1.1.Application of UAV for biomass inventory
Vegetation monitoring typically relies on collecting field data on the presence, abundance and
health of plant species. However, in wetlands, difficult access limits the collection of classical
botanical data, and airborne or satellite imaging is widely used for monitoring. In addition to
classical aerial photography, the potential of multispectral and hyperspectral methods for
vegetation classification and mapping has also proved successful in many surveys (Zlinszky,
2012).
During the last 20 years, UAV technologies have developed rapidly and now, due to the high
flexibility of the systems employed in UAVs, these vehicles can be useful in civil fields. For
instance, UAVs are employed in land monitoring, remote sensing, agriculture and public
security. Technological progress in the electronic and aerospace engineering fields has allowed
the development of low-cost small sized UAVs (mini-UAVs), which can carry on-board imaging
or non-imaging sensors. These technological advantages have led the civil community having an
increasing interest in mini-UAVs.
Existing UAV systems can be useful for different scales of application. The cost of the systems
can vary between €100 up to several millions of Euros. The major advantages of UAV systems
compared with manned aircraft systems are that UAVs can be used without risk to human life in
different situations and in inaccessible areas, at low altitudes, and close to objects where manned
systems cannot be flown. For instance, for obtaining images at an altitude of 100 m to map
biomass resources or flying above the lake areas. Furthermore, in cloudy and rainy weather
conditions when the wind and rain is not too intense and when the distance to the object permits
flying below the clouds, data acquisition using UAVs is still possible. Such weather conditions
do not allow data acquisition (Fig. 1) using large and heavy cameras integrated into manned
aircraft due to the greater flight altitude required. In addition, one fundamental advantage of
using UAVs is that they are independent of the physiological limitations and economic expense
6
of human pilots. Moreover, additional advantages are the real-time variability and the ability for
fast data acquisition, while transmitting the image, video and orientation data in real time to the
ground control station (Hassinen, 2008).

Figure 1. Unmanned aerial vehicle during imagery acquisition at Mekijarvi Research station.
Current standard Unmanned Aerial Vehicles (UAV) permit the registration and tracking of the
position and orientation of the implemented sensors in a local or global coordinate system.
Hence UAV photogrammetry can be understood as a new photogrammetric measurement tool.
UAV photogrammetry offers various new applications in the close range domain, combining
aerial and terrestrial photogrammetry and introducing new (near-) real time applications and
low-cost alternatives to classical manned aerial photogrammetry (Eisenbei, 2009).
UAV is considered an important tool with great potential in resources inventory. As it can fly at
low height, its gives very high resolution data from which very detailed information extraction is
possible with high accuracy. An aerial photograph is a useful and illustrative means of observing
the terrain and its details. The automatic methods of image interpretation provide unique
opportunities for the rapid assessment of energy content in standing biomass (reed grass and
forest stands, etc). An aerial photograph is a useful and illustrative means of observing the terrain
and its details. In an aerial photo you can see the vegetation, buildings, roads and other details
that do not stand out in maps. During 2007, technology for obtaining very high resolution aerial
7
images using an unmanned radio-controlled airplane was tested at the Mekrijärvi Research
Station by a group of researchers coordinated by Prof. Taneli Koström. The CropCam UAV was
used to obtain images of the study area. The CropCam is a radio-controlled model glider plane
equipped with a GPS, a miniature autopilot and digital camera. Hand launched, and automatic
from take-off to landing, the CropCam provides high resolution GPS based images on demand.
With this UAV the images from various spatial resolutions can be obtained, from 2 cm up to 20
cm per pixel.
1.2.Utilization of common reed biomass for energy production
Common reed (Phragmites australis) is a tall grass species of great economic and ecological
importance that is widely distributed in European wetlands (Haslam, 1972). The fuel properties
of common reed are close to the Reed canary grass (Phragmites arundinacea). In Finland,
common reed has been cofired with wood chips or peat to generate electricity since the late
1990s (Pahkala et al., 2008). Common reed harvesting was never easy due to its relation with
water ecosystems. Shore wetland vegetation plays an important role in the functioning of lake
systems. The ecotone between land and water creates a large variety of microhabitats, and the
high biomass production of wetland vegetation feeds energy into the food web (Strayer, 2010).
Being a rotting stationary biomass, reed beds reduce water quality, deplete oxygen supplies in
the water and release methane into the atmosphere. The expanse of reed beds also has an adverse
effect on the landscape and biodiversity. Many people have wondered whether the reed beds
could be utilised in some way to provide bioenergy (Hagelberg, 2007).
In Finland a hectare of reed generates approximately 5 tons of dry reed material. The fuel value
of dry reed is about 4.5 MWh/t, which means that the annual energy potential of reed beds is
more than 20 MWh per hectare. This corresponds to the heating needs of an average-sized
family home (Pahkala et al., 2008). When dry, reed is very light and therefore, without
preliminary treatment, its transportation costs are high. Therefore one of the crucial questions in
the management of reed grass fields is resources assessment. Reed could be used as an additional
local source of energy in coastal areas. The balance between the preservation, utilisation and
management of coastal areas is a fundamental question and is one that is related to the creation
of strategy in Finland (Pahkala et al., 2008).
The quality of reed and its biomass may vary greatly depending on location. Different locations
set their own challenges for the utilisation of bioenergy; it is difficult, or impossible, to use the
same equipment in all reed beds. Reed can be collected for energy production throughout the
year. The way in which reed is used for energy depends on the time of harvesting and the boiler
8
used. During summer, the green, wet reed is suitable for producing biogas and biofuels (Fig.2).
Reed harvested during winter can be burned in different types of boilers, for instance as shreds
(mixed with woodchips), or as pellets, briquettes or bales (Fig. 3). Ashes generated by burning
can be spread on fields as a fertiliser.

Figure 2. Summer reed cutting with a boat-mounted mowing machine, Finland. Photo: Helena
Sarkijarvi (Hagelberg, 2007).

Figure 3. Winter reed harvesting by tractor in Hamina, Finland. Photo: Teemu Kettunen
(Hagelberg, 2007).
If reed is finely shredded and mixed with woodchips it works well as a fuel in modern boilers.
The key is to chop the reed short enough and mix it with the other material in the correct ratio for
the boiler type and intended burning process (Fig. 4). Reed can also be mixed with cereal dust
and peat. Using straw bales as a source of energy is also common, and there are many kinds of
boilers available for different users. Perhaps the most cost-effective way of burning reed is to
burn it in bales; the reed then needs very little processing. Modern straw bale boilers, in which
9
the bales are shredded and then fed into the boiler by blowing them into the flames, may also be
suitable for burning reed bales. These boilers can also cope with the volume of ash generated by
burning reed (Hagelberg, 2007; Pahkala et al., 2008).

Figure 4. Chipping dry reed for burning tests in Halikko, Finland. Photo: Eija Hagelberg
(Hagelberg, 2007).

Figure 5. Reed sent to a boiler together with woodchip. Finland. Photo: Eija Hagelberg
(Hagelberg, 2007).
Hay and manure are used as energy in biogas installations elsewhere in the world, and also
increasingly in Finland. Common reed is also suitable for the production of biogas (Seppala et
al., 2009). Reed that is to be turned into biogas must be collected in the summer, when the plant
is green. The by-product of the biogas production process is pure fertiliser, which can be spread
on fields. Besides providing energy, this process will return the nutrients to the fields that have
been washed from the field to the shoreline waters. When planning new biogas installations, the
availability of reed should be considered when selecting the location of the plant. Suitable
10