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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>DEER</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>with Thermal Imaging</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Benjamin Kämä</string-name>
          <email>benjamin.kama@oulu.fi</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ella Peltonen</string-name>
          <email>ella.peltonen@oulu.fi</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Thermal Imaging, Image Recognition, Smart Vehicles, Animal Vehicle Collision</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Empirical Software Engineering in Software</institution>
          ,
          <addr-line>Systems, and Services</addr-line>
          ,
          <institution>University of Oulu</institution>
          ,
          <country country="FI">Finland</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2025</year>
      </pub-date>
      <volume>1</volume>
      <issue>0</issue>
      <fpage>0000</fpage>
      <lpage>0002</lpage>
      <abstract>
        <p>Around 4,000 reindeer-vehicle collisions (RVCs) happen annually, leading to losses in reindeer and human lives. The annual vehicular property damage from RVCs is estimated to cost 15-20 million euros. Despite this, there have been only a limited number of attempts to automate RVC prevention. To save Rudolf and the rest of the reindeer, this paper tackles RVCs by proposing a thermal imaging-based solution that would be feasible to implement in a vehicular setting. The system relies on an inexpensive FLIR thermal camera that can be attached to most smartphones. Compared to regular cameras, thermal camera performance is not hindered by low lighting conditions or poor weather, especially winter conditions in the reindeer native lands in Lapland. For recognition of the reindeer, we utilise a Convolutional Neural Network (CNN) algorithm that we evaluate with open-sourced and self-collected FLIR thermal camera datasets. Our solution has high accuracy on diferentiating reindeer from other pedestrians, 0.998 at best, and thus compares well to other camera-based image recognition algorithms used for general animal detection. In future work, the model can be integrated into a driver warning system or an autonomous vehicle's control system to avoid the reindeer on the road and prevent collisions.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        In Finland, there are around 4,000 reindeer-vehicle collisions (RVC) per year in which both reindeer
(Rangifer tarandus tarandus) and human lives are lost and property damage occurs. Annual vehicle
damage costs from RVCs are around 15-20 million euros, and reindeer owners claim circa 2.5 million
euros in insurance settlements for reindeer lost in road trafic accidents [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. There is also the emotional
cost for the humans involved, as RVCs can cause a loss of feeling safe on the roads. As reindeer are
pack animals, many can simultaneously become involved in the same RVC event, making the collisions
more dangerous and increasing the monetary and emotional load. Although the costs are high, no
successful solutions have been found to automate RVC prevention. The current general method for
warning oncoming trafic about reindeer sightings is to flash high-distance beams manually. However,
automatically detecting any animals on the road, let alone brown-grey reindeer (see Figure ??), is
challenging, especially in dark and less optimal weather conditions [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. In daylight, standard
camerabased methods can be utilised [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Still, their capability in less than optimal lighting conditions, such
as in the grey evenings and pitch-black nights when reindeer are the most active, remains an open
question. To make it possible to warn the driver and other trafic about reindeer on the road or even
automatically avoid them in modern autonomous driving vehicles, there is a need for a reliable, weather
and light-tolerant solution for reindeer detection.
      </p>
      <p>
        This work presents a thermal imaging-based method and a CNN image recognition algorithm for
detecting reindeer and diferentiating them from other pedestrians and animals, especially people
walking on the rural roadside. For the sake of automating evading movements of the vehicle, it is crucial
to know when the object is indeed a human or reindeer. We presume that a pedestrian walking the
roadside would continue progressing straight [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ], compared to reindeer, which are semi-domesticated
animals [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] and prone to unexpected movements and running in front of trafic. In contrast to completely
wild animals, such as moose, elk, and regular deer, reindeer are not scared of cars and may wander
      </p>
      <p>CEUR
Workshop</p>
      <p>ISSN1613-0073
on the roadside for prolonged periods of time. Reducing reindeer collisions is an especially pressing
problem in Northern Scandinavia and Finland; they are considered culturally essential animals, an
expensive delicacy (a herder owns each reindeer), and their semi-domestic nature comes without fear
of trafic. In the future, we can expand to other wildlife, such as elk/moose, of which avoidance difers
from tightly-packed reindeer.</p>
      <p>
        Regular cameras perform well in daylight and during good weather, but bleak autumns and winters
hinder visibility and prediction accuracy in poor weather and low-light conditions. These are also the
periods when most RVCs happen. Our proposed solution combines a CNN-based image recognition
model, an of-the-shelf FLIR thermal camera, and an Android smartphone. Compared to some existing
drone-based reindeer detection methods [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ], our solution is lightweight to implement, and the device
setup is cheaper. The thermal camera images used to train, test, and evaluate the model are an
opensource dataset from Roboflow and manually self-collected FLIR thermal camera images from local
reindeer. To summarise, our main contributions are the following:
• We present a CNN-based machine vision algorithm that detects reindeer from thermal images.
• We show that detecting reindeer from thermal camera images is possible in an accurate manner,
with an accuracy of 0.998 at best, with similar or higher evaluation results than reported in the
previous works.
• By evaluating our solution with both an open-source dataset and self-collected data, we can show
that our method generalises over diferent datasets without losing much of its accuracy.
• We compare our solution to other image-based animal detection and collision avoidance systems
and show that we can get equally good results with an inexpensive FLIR camera addition to an
Android smartphone.
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. Reindeer-collision (RVC) Prevention Methods</title>
      <p>Reindeer, hoofed ruminant mammals, can be classified under the family Cervidae. Diferent methods can
be utilised for cervid-collision prevention. Next, we discuss reindeer-vehicle collision (RVC), or in more
general terms, cervid-vehicle collision (CVC) prevention methods. Some of them include Advanced
Driver Assistance Systems (ADAS) technology, but many are not integrated into the vehicles at all.
Table 1 summarises some most popular CVC prevention methods, out of which we focus on digital ones.
The column “Still in use?” refers to their current status in Finland.</p>
      <p>Method
Relocation
Hunting
Overpasses/crossings
Vegetation removal
(Street) lights
Fencing
Road signs
Porokello
Varoporoa
Radio transmitters
Night Vision
Riistavaroitus</p>
      <p>
        Source Still in use?
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] No
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] No
[
        <xref ref-type="bibr" rid="ref7 ref8">7, 8</xref>
        ] Yes
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] Yes
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] Yes
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] Yes
      </p>
      <p>
        Yes
[
        <xref ref-type="bibr" rid="ref10 ref11">10, 11</xref>
        ] No
      </p>
      <p>
        No
[
        <xref ref-type="bibr" rid="ref12">12, 13</xref>
        ] Not clear
[
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]
[14]
      </p>
      <p>Not clear
Yes</p>
      <p>Note
Not used in Finland
Hunting not applicable to reindeer in Finland as they are considered livestock
Located in southern parts of Finland only
Done near the roads
Focused near cities and settlements; thus, rural areas rarely have lights. RVCs are
a higher risk in rural areas, and the road speeds are higher on rural roads.</p>
      <p>
        Used in Finland for other cervids, e.g. elk/moose [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]
In use in Finland country for reindeer, elk, and deer
Mobile phone application where professional drivers reported reindeer sightings
and users were notified of them
Website unavailable at the moment.
      </p>
      <p>These were radio transmitters fitted on the reindeer and LED warning lights
installed on the roads. They had a lot of technical issues they were working on.</p>
      <p>Thermal camera setup connected to NV ECU. First such system in production cars.</p>
      <p>Made for Audi, BMW, and Daimler. Used FIR or Far Infrared Camera.</p>
      <p>Mobile application that warns the user when there is a risk for CVC. Not
fullyautomatic as it requires human input.</p>
      <p>
        The first example is a service explicitly provided for aiding drivers to avoid reindeer on the roads, a
smartphone application called Porokello. It was a mobile app that crowdsourced reindeer sightings.
The professional drivers of trucks and delivery vehicles were asked to log reindeer sightings in the
application, and the application would then notify other users (such as personal vehicle drivers) if there
was a heightened risk for RVCs [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. A notification would be sent to all the users for 30 minutes and
around 750m of the observation spot. The app was downloaded over 65 thousand times and had 300-600
daily users during its operational period. During the apps’ operation in 2017-2018, RVCs went down 30%
from 2011-2015. However, for roads with fewer RVCs, the change was either less than average or the
number of RVCs had increased [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Thus, it is impossible to say that warnings have had a direct efect
on RVCs or a change in the number of accidents. However, nine out of ten questionnaire respondents
said they had changed how they drove after getting a Porokello warning, for example, paying better
attention to driving and lowering driving speed [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
      </p>
      <p>A similar application to Porokello is the new Riistavaroitus application [14] that launched only
recently, at the beginning of 2025. In the Play Store description1, the application is claimed to be able to
warn about active reindeer areas, as well as about the end of fencing, active hunting sites, and about
RVCs that have already occurred. However, such a solution still requires human input from hunters
who have been notified about an RVC and who go to handle hurt animals [ 14]. Thus, there can be
significant delays in issuing the RVC warnings, which reduces their information value. Another digital
service is the Varoporoa website2. It is map-based, showing all reindeer vehicle crashes in the last 21
days, in addition to some historic data tables. The last year shown is 2021, with no data for 2022 or
2023. The map does not show any data at the moment. However, a separate page shows yearly RVC
statistics between 2011 and 2024.</p>
      <p>
        A diferent type of RVC prevention method is radio transmitter collars installed on 235 reindeer in
Saltfjellet, Norway [
        <xref ref-type="bibr" rid="ref12">12, 13</xref>
        ]. They had receivers on the roads equipped with red LED lights that started
blinking when a reindeer with a transmitter collar was within 50-100m of the receiver. They had 41
receivers on a 4.5km long road section. Reindeer deaths were recorded before and during the two-month
experiment from February to April 2018. Other transmitters were tested on 200 reindeer on the same
road from December 2018 to April 2019, resulting in 15 deaths from December 2017 to February 2018,
when their experiment started, but no RVCs. By 2019, there were no deaths of transmitter-collared
reindeer. However, there were several dificulties with the transmitters. By the end of their first research
period, 25% of the receivers had stopped working, and they suspected this was due to battery shortage.
During the second experiment, around mid-February 2019, 8% of receivers and 35% of transmitters were
not working [
        <xref ref-type="bibr" rid="ref12">12, 13</xref>
        ].
      </p>
      <p>
        Utilising thermal cameras for CVC prevention has been proposed but rarely experimented with in
real-life conditions. For example, Zhou et al. [15] built a thermal camera setup using a large FLIR
thermal camera with a frame grabber, two motors, and power sources. The work focused more on the
technical production of this thermal camera setup than on the eficiency of the algorithmic solution.
Lyo et al. [
        <xref ref-type="bibr" rid="ref6">16, 6</xref>
        ] have recently proposed a method for deer identification by using Unmanned Aerial
Vehicles (UAVs) equipped with thermal cameras. However, this method, even if successful, requires the
use of a UAV and is thus less than optimal for driving situations, as reindeer tend to move in a relatively
large area. The oficial reindeer herding area in Finland covers over 120.000 square kilometres of land
and around 80.000km of public roads, making it impossible to cover by UAVs. Thus, a vehicle-based
solution seems to be the most feasible.
      </p>
      <p>
        Night Vision (NV) Forslund and Bjärkefur [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] has been the first animal detection system for cars in
customer markets. It uses a far-infrared camera (FIR) that can be mounted in the front on top of the
vehicle grille. The FIR was connected to an NV electronic control unit (ECU). The NV ECU was further
connected to the display, the instrument cluster, and the Head-Up Display (HUD). The enhanced video
with highlights around particular objects was then shown to the driver on a display. Warnings were
given to the driver with warning symbols or lights in the instrument cluster or HUD. For the object
detection, the NV used boosting [17, 18] and a cascade structure [19]. Using a smaller feature evaluation
set, the model combines several weaker classifiers to reject the non-animal images. However, the
model’s accuracy was not reported beyond the accepted error rate of one false detection per year, and
1https://play.google.com/store/apps/details?id=com.innotrafik.riistavaroitus&amp;hl=fi
2https://www.varoporoa.fi/
vehicle manufacturers had accepted the product. Additionally, the system can detect ”almost all relevant
animals” but does not state which animals it can or cannot detect. The reactions of the driver/vehicle
are dependent on the animal detected. For example, a horse/rider pair can be slowly overtaken at a
safe distance, and sighting a moose requires a complete stop at any cost, as a crash would easily be
fatal. Reindeer, conversely, have to be overtaken with caution as they can change their direction at any
moment. Due to a lack of reported evaluation metrics, it is hard to evaluate how well the NV system
performs against other models. Night Vision was tested with data for eight years through diferent
seasons and weather conditions. They reported having gathered several hundred thousand labelled
images and varied animals, but the data is not publicly available.
      </p>
      <p>
        However, Riistavaroitus is the only technological solution that is still in use today. The Porokello
app was terminated, and the Varoporoa website is not available at the moment. It is unclear if NV and
the radio transmitter collar project by [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] continue. On the other hand, the radio transmitter project
seemed to be successful as no reindeer were killed on the test roads during the test period. It is also
possible that Autoliv has continued to develop NV, perhaps integrating it into another project with a
diferent name. The reasoning is that since ADAS is increasing in popularity and importance [ 20], it
makes sense that there is continued interest in sensor technology development [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ].
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Methods and Materials</title>
      <sec id="sec-3-1">
        <title>3.1. Research Context</title>
        <p>In this research, we consider animal-vehicle collisions (AVCs), more specifically cervid or reindeer
vehicle collisions (RVC), that happen on public roads, including motorways, dual carriageways, and
similar. The vehicles considered are all road vehicles, varying from personal cars to trucks and other
heavy machinery. AVCs can happen on any road with vehicle trafic, although reindeer are more
common in rural settings. Some areas also have more reindeer, and thus, the risk for RVCs is higher.</p>
        <p>
          The current estimation of semi-domesticated reindeer in Finland is 203.700 animals [22]. Reindeer
are well accustomed to living in the Arctic areas with feet that have evolved to walk in deep snow. Their
movement on the roads can be determined by various factors such as the time of year or day, foraging,
or breeding season [
          <xref ref-type="bibr" rid="ref10">10</xref>
          ], but may also not follow a specific pattern, including crossing the same roads
several times a day. The stag can weigh between 90-180kg and grow to a height of around 110cm. The
doe is smaller at 90cm and 60-100kg. As a newborn, they weigh only 4-6kg. The doe can live up to
20 years, and the studs over 10 years. Their colour can difer widely, ranging from black to white, as
can be seen in Figure 6a and 1, and both the stag and the doe grow antlers that the stags drop in the
Autumn, and the does drop in the Spring [23]. In Fennoscandia, reindeer live in domesticated herds,
except in Norway, where there are also mixed herds with reindeer from both wild and domesticated
origins [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ]. Reindeer is an example of wildlife habituation to roads and vehicles, as they may have flight
responses to vehicles, but only in rare observations [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ].
        </p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Research Methodology</title>
        <p>This research follows, on a general level, the Constructive Research Approach (CRA) [24, 25]. The focus
is on creating an artefact specifically to solve a specific real-life problem, in this case, the occurrence of
RVCs. As we have identified in Section 2, there is a knowledge gap on existing RVC prevention methods:
1) The current systems are either not in use anymore (most digital services) or inefective for broader
applicability (such as radio transmitter collars), 2) Even if a commercial solution (Night Vision) seems
to exist, there are no proofs of its performance for RVC prevention, 3) Camera-based animal-detection
algorithms are problematic on nighttime when RVCs are the most common, 4) Thermal-based state
of the art solutions focus on UAV perspective, leaving little applicability to real-life driving situations,
and 5) No reindeer-specific image recognition algorithm has been presented in the literature that
would be evaluated in dark/night environments. To fill this gap, we developed an artefact consisting
of a CNN-based algorithmic solution that we validated with actual reindeer image data, combining
open-sourced and self-collected images. The fit of the algorithm was evaluated with statistical metrics.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Open-source Datasets</title>
        <p>Only a limited number of thermal image open-source datasets are available, especially those that
include deer images. FLIR provides its own ADAS dataset, but no deer images are included. Choi et al.
[26] presented a KAIST multi-spectral dataset, but there is no information about the classes used for
detection. Roboflow is an image database with 90,000 public datasets with over 220,000 images with
805 class labels [27]; three such datasets were used in this study.</p>
        <p>Svarzas Dataset is a deer image dataset (see Figure 2, right-hand side) published by Balzs Sznyi
in 2023 [28], and it is available under a CC BY 4.0 license. It contains 2,599 thermal camera images
of deer in an enclosure. The images are 416 by 234 pixels. The deer are annotated using Pascal VOC
format. According to the README file, some preprocessing is done to the images. The pixel data was
auto-oriented, and EXIF orientation was stripped. They were also resized to 416x416 with Fit Within;
image augmentation techniques were not used.</p>
        <p>Human Detection in IR Images Dataset contains thermal camera images of humans in various
poses. It was published by username Karky in 2023 [29] under the MIT license. It contains 895 images,
and the humans are annotated using the COCO format. The images are 640 by 640 pixels. Just as with
the first dataset by Sznyi, the pixel data was auto-oriented, EXIF-orientation stripped, and the images
were resized, although here they were resized to 640x640 with Stretch. Karky did not use any image
augmentation techniques, just like Sznyi.</p>
        <p>Thermal Human Detection Dataset is published by the username PNUSafetyNet in 2022 [30]. It
contains 229 thermal images of humans in diferent poses. The images are sized at 640 by 480 pixels.
These images were black and white instead of the coloured other datasets. The human images were
annotated using the COCO format. The only pre-processing applied was auto-orienting the pixel data
and stripping EXIF orientation. Image augmentation was not used.</p>
      </sec>
      <sec id="sec-3-4">
        <title>3.4. Self-collected Dataset</title>
        <p>We collected thermal camera images of reindeer to ensure that the algorithm could generalise over more
than one deer thermal image dataset, as there was a limited number of open-source datasets with deer
images available and no datasets with reindeer. We used the Teledyne FLIR One Pro LT (generation
3) thermal camera attached to the OnePlus 7t Android phone. The setup is shown in Figure 3. The
resolution of One Pro LT is 80 x 60 or 4800 pixels. The horizontal field of view (HFOV) is 50° ±1°, and
the vertical field of view (VFOV) is 38° ±1°. There are three diferent image modes: infrared, visual, and
MSX or Multi-Spectral Dynamic Imaging mode. The file formats are radiometric JPG and MPEG-4 in
iOS and MP4 in Android.</p>
        <p>We used FLIR’s own FLIR One application. The images were handheld without a tripod and in
landscape and portrait orientation (see Figure 2, left-hand side). The scan was infrared only, and the
colour was iron. The images were taken in Ranua Zoo. The animals were photographed in their
enclosure from varying distances and angles. There were images of both single and multiple animals.
The reindeer were all adults, but one juvenile was in the European Forest Reindeer enclosure. The
pictures were taken during one day in October of 2023, when the weather was cloudy without rain.
There were altogether 408 images, of which 135 were of the European Forest Reindeer (Rangifer fennicus
fennicus), and 273 of the similar-looking domesticated reindeer (Rangifer tarandus tarandus). The size
of the images was 640 by 480 pixels. The self-collected dataset is small for a machine-learning dataset,
but data augmentation was used to correct this issue. We also used the open-source deer dataset from
Roboflow to increase the number of deer images available for training, testing, and evaluation.</p>
      </sec>
      <sec id="sec-3-5">
        <title>3.5. Model Creation</title>
        <p>The Roboflow dataset had 842 images of deer and humans, a total of 1684 images. In the Ranua dataset,
the deer images were self-collected, and the human images were collected from an open-source dataset
from Roboflow. It had 281 images of deer and humans, totalling 562 images. In the mixed dataset, the
deer images were a combination of images from the self-sourced and Roboflow sources, and all the
human images were from Roboflow. It had 654 images of deer and humans, totalling 1308 images. The
images used for model training, testing, and validation were selected from the Roboflow and Ranua
datasets randomly in a 1:1 ratio. This ratio was selected to create a balanced dataset so that the model
would avoid overfitting on a particular class. The image recognition models were created using Keras
and KFold from Scikit-learn. 27 models were created and then compared against each other. They were
created iteratively so that the evaluation metrics were looked at to see which models performed the
best and how adding each layer influenced the metrics. All models except model 8 were Convolutional
Neural Networks (CNNs). Model 8 was a simple Neural Network (NN) but was eventually left out of
further testing as it did not perform well. Figure 4 shows model number 25.</p>
        <p>Rescaling and data augmentation: The first layer of all 27 diferent models was a Rescaling layer,
which rescaled all the images to 1. / 255. The last three layers were the Flatten layer, then two Dense
layers, first with unit size 128 and activation relu, or rectified linear unit activation, and then one with
unit size one and activation sigmoid. The sigmoid activation was chosen as the last one, as this was a
binary classification task, and sigmoid activation provides a value between 0 and 1 for the likelihood
of the image being of the chosen class. For the data augmentation, models from 9 to 27 used image
augmentation layers after the Rescaling layer (see Figure 4). Image augmentation layers improve the
training with small datasets [31]. The layers were RandomCrop, RandomFlip, RandomRotation, and
RandomZoom, varying in diferent models. Model 9 used RandomCrop at sizes 200 and 200, RandomFlip
at horizontal, RandomRotation with a factor of -0.5 and 0.5, and RandomZoom at 0.25. Model 10 used
RandomRotation with a factor of -0.5 and 0.5 and RandomZoom at 0.25. Model 11 used RandomCrop
at sizes 200 and 200 and RandomFlip horizontally. They both had five blocks of two Conv2D layers
followed by MaxPooling2D. The rest of the models from 12 to 27 used RandomRotation with a factor of
-0.5 and 0.5 and RandomZoom at 0.25.</p>
        <p>Convolution and maxpooling: All of the convolutional layers used were square Conv2D layers,
and they used padding with the same value. The activation used was relu in all of them. The number of
iflters and the kernel size varied between models and sometimes between diferent convolutional layers
in the same model. This was done to discover the best combination of values for identifying reindeer
from thermal images. The models mostly followed the pattern of having a Conv2D layer, or several,
followed by a MaxPooling2D layer. Model 1 had a Conv2D layer with 16 filters and a kernel size of 3,
followed by a MaxPooling2D layer. Model 2 added another convolutional layer with 32 filters, a kernel
size of 3, and a MaxPooling2D layer. Model 3 added another convolutional layer with 64 filters and a
kernel size of 3 and a MaxPooling2D layer, and model 4 further added a convolutional layer with 128
iflters and a kernel size of 3 and a MaxPooling2D. The Conv2d layers in models 5-7, 9-24, and 26 had
three filters and a kernel size of 3. Model 25 had the first layer with 11 filters, a kernel size of 11, five
iflters, and a kernel size of 5, followed by three with three filters and a kernel size of 3 convolutional
layers. Models 5-25 had five blocks of Conv2D and MaxPooling2D. In each block, models 6 and 9-11 had
two Conv2D layers followed by a MaxPooling2D. The rest of the models had one Conv2D layer followed
by a MaxPooling2D layer. Model 26 had seven blocks of Conv2D and MaxPooling2D combinations, and
model 27 had six blocks of that layer combination.</p>
        <p>Normalisation : In models 7, 13-20, and 25-27, normalisation layers were explored. Models 7, 13,
and 25-27 used a single BatchNormalization layer after the first Conv2D layer (see Figure 4). Model 14
had the BatchNormalization layer between Conv2D and MaxPooling2d for every five blocks. Models 15
and 16 similarly used LayerNormalization, so in model 15, there was only one normalisation layer in
the first convolutional block. In model 16, it was in all five blocks. Models 17 and 18 repeated the same
process with UnitNormalization, and models 19 and 20 similarly used GroupNormalization. Diferent
Dropout layers were explored in models 21 to 24. Model 21 used Dropout at a rate of 0.25 after each of
the five Conv2D layers, and model 22 was similar, except the dropout rate was 0.5. Models 23 and 24
used SpatialDropout2D similarly; this layer came after each of the five Conv2D layers, and the dropout
rate was 0.25 in model 23 and 0.5 in model 24.</p>
      </sec>
      <sec id="sec-3-6">
        <title>3.6. Model Evaluation Setup</title>
        <p>After the model was created, model.compile was called with optimized adam, the loss function was
set to BinaryCrossEntropy, and the chosen metrics were also given as attributes. Then model.fit was
called, and the history information was taken. Test accuracy for the whole model was recorded, and
precision, recall, and F1-score were recorded separately for the deer and the human classes. 10-fold
cross-validation was used with varying numbers of epochs. All 27 models were initially tested on 10
epochs while training with the Roboflow and testing with the Ranua data. Out of all the models, models
13, 25, and 27 were selected for further testing. They were tested with epochs 10, 25, 50, 75, and 100.
After the tests were run, the model was trained on Roboflow and tested on Ranua data. Models 13, 25,
and 27 were run with the same epoch numbers while training with Ranua and testing with Roboflow
data, as well as with a mixed dataset. 25% of the data was reserved for testing.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Results</title>
      <p>
        The test accuracy results for all models with 10 epochs are shown in Figure 5. The results vary widely
between 0.447 and 0.998. When considering that 0.5 means that the accuracy is 50%, which is the
accuracy of a guess, it can be seen that some of these models are as good as a guess. However, there are
several models with very good accuracy results. Out of the 27 models, as mentioned in the previous
section, models 13, 25, and 27 were chosen for further tests. Some model-epoch combinations might
have poor test accuracy, poor recall, and F1-score, but precision is 1, or poor test accuracy, precision,
and F1-score, but recall is 1. Thus, it is necessary to look at all the metrics. Our best accuracy results
are close to 0.998, which aligns with animal recognition algorithms presented in the state of the art,
even if they use an ”easier” case of the camera instead of thermal images [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
      </p>
      <sec id="sec-4-1">
        <title>4.1. Training with Roboflow and Testing with Ranua Data</title>
        <p>Table 2 and Figure 6a show the test accuracy for training with the Roboflow and testing with the Ranua
data. The test accuracy varies between 0.493 (model 27 with 100 epochs) and 0.998 (model 13 with
10 epochs). However, 10 of the 15 diferent models and epoch combinations had an accuracy above
0.85. Table 2 also has the precision, recall, and F1-score. Most models with low test accuracy also had
low precision, recall, and F1-scores. The models with better accuracy perform better and best with
ten epochs. For example, model 13 at 10 epochs had the best test metrics out of model and epoch
combinations with an accuracy of 0.998, with deer precision of 1, recall of 0.996, and F1-score of 0.998,
and the values for the human class of 0.996, 1, and 0.998, respectively.</p>
        <p>Increasing the epoch count seems to be somewhat inconsistent with the metrics. The test accuracy
drops when the epochs increase from 10 to 25 for all three models. They further drop for models 13
and 25 when the epochs are increased from 25 to 50, although for model 27, the accuracy improves.
Accuracy seems to improve or stay the same when the epochs are further increased to 75. Yet, they
drop again for models 25 and 27 when the epoch count is increased to 100, but model 13 performed well.
It had an accuracy of 0.979, which is better than model 25 at epoch 10. Our results compare well with
previous work on animal recognition. Kalla et al. [32] presented Nasnet, a CNN-based Nasnet-Mobile
model, for identifying horses on the roads. Their training accuracy was approaching 1 at 6 epochs,
and for testing accuracy, it was approaching 1 at 45 epochs. Their precision was around 86.5%. When
comparing these results to our results shown in Table 2, ours is higher for all the models with 10 epochs
when the range is between 0.946 and 1, but there is more variation with higher epoch counts.</p>
        <p>Antônio et al. [33] presented K-Nearest Neighbors (KNN) and Random Forest (RF) algorithms for
animal detection. They reported their results using F-measure. They had two results for KNN (0.611 and
0.624) and two for RF (0.560 and 0.589). 25 out of 30 of the F1-scores shown in Table 2 are higher than the
results from Antônio et al. 20 of the results have an F1-score above 0.8. Nguyen et al. [34] presented a
CNN for detecting and identifying wild animals from images. They used a simplified version of AlexNet
called Lite AlexNet, VGG-16, and ResNet-50. They tried both imbalanced and balanced datasets. For
the binary task of animal recognition, the accuracy results were for VGG-16 96,6% for imbalanced and
95.9% for balanced, for ResNet-50 they were 96.1% and 95.7% respectively, and for Lite AlexNet they
were 94.9% and 92.7% respectively. For wildlife identification tasks, accuracy varied between 82.5% for
Lite AlexNet for identifying the six most common species and 90.4% for ResNet-50 for identifying the
three most common species with an imbalanced dataset [34]. Table 2 shows that all three of our best
models with epoch 10 have better accuracy.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Training with Ranua and Testing with Roboflow Data</title>
        <p>The accuracy metrics for the model epoch combinations when training with Ranua and testing with
Roboflow data are shown in Figure 6b and Table 3. The test accuracy varied between 0.5, which several
model epoch combinations had, and 0.88, with model 27, with 10 epochs. From Table 3 we can see that
the best accuracy is for model 27 with 10 epochs at 0.88, and the following best are for model 25 with
25 epochs at 0.859 and model 25 with 100 epochs at 0.855. The same happens in test accuracy, and
performance correlates with other metrics. However, several model epoch combinations might have
perfect precision or recall for one class but a much lower value for the other.</p>
        <p>Compared our results to previous works, Kalla et al. [32] have better accuracy than any model or
epoch combination in Table 3. When comparing the precision of 86.5% from Kalla et al. [32], we have
better precision in model 27 with 10 epochs for deer (0.9) and almost equal for humans (0.862). Despite
the lower accuracy, the precision can compare well for model 27 at 10 epochs. When comparing our
F1-scores to the F-measure reported by Antônio et al. [33] (ranging between 0.5601 and 0.6243), from
our results, 20 out of 30 F1-scores are higher. The F1 scores, however, are not as high for the model
here as for the one trained with Roboflow and tested with Ranua. The accuracy values for Nguyen et al.
[34] with a range of 92.7% to 96.6% for the binary identification were all better than in Table 3.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. Training and Testing with a Mixed Dataset</title>
        <p>The results for the mixed dataset are very good overall, as shown in Table 4 and Figure 6c. The
test accuracy varies between 0.905 (model 25 with 50 epochs) and 1, with 11 of the 15 model epoch
combinations having this. As the combined dataset is quite large, it is probably one cause for the
better performance compared to the results from training with Ranua and testing with Roboflow. The
results compare well with related literature. The test accuracy is 1 for 11 out of the 15 model and epoch
combinations; at worst, it is 0.905. It compares well to the test and training accuracy 1 by Kalla et al.
[32]. The precision results are superior compared to the 86.5% by Kalla et al. The F1-scores are all
higher by a large margin than the F-measure results for Antônio et al. [33]. When compared to Nguyen
et al. [34], it can be seen that all but one of our accuracy results in Table 4 are higher.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Discussion</title>
      <p>As can be seen from the results, the mixed dataset performed the best out of the three, and the models
that were trained on Roboflow and tested on Ranua material were the 2nd best. One possible reason for
the lower results in the case of models trained on Ranua and tested on the Roboflow data could be the
small size of the training material. On the other hand, size is not necessarily the only thing, as the mixed
dataset performed better than the one trained with Roboflow, tested with Ranua, despite the latter being
a larger dataset (2 times 842 images vs. 2 times 654). As the results varied between the models trained
on diferent datasets, it is hard to recommend the best epoch counts. However, it seems that high epoch
counts are not needed to attain well-performing models. The limitation of this work is that it only
has two classes. This makes it easier to identify reindeer from images, as only reindeer and human
images are included. However, our future work includes adding more classes to the model. At least elk
or moose would be an essential addition, but other animal classes could include fox, rabbit, cat, and
dog. If the detection of diferent Arctic wildlife, including birds, were enabled, then the data collection
could serve a secondary purpose of collecting critical information about the occurrence of rare species.
This could be used to help conservation eforts. However, including additional classes creates a need to
gather a larger dataset, as thermal images of varying species are sparse in the open-source datasets.</p>
      <p>Another future work is to gather more thermal camera images of reindeer and humans. These could
also be taken in a driving situation, providing the most realistic images. Increasing the dataset size
would improve the model, as machine learning applications usually perform better with larger datasets.
Increasing the dataset with additional reindeer and human pictures, as well as pictures for additional
classes, would then likely afect the model training time. However, model complexity and epoch counts
could potentially be optimised for better time performance, as shown in our work. Our best evaluation
metrics for the models were so good with epoch 10 and reasonable processing times. As such, our future
work will focus more on the datasets and real-time animal detection situations. In the future, our goal
is to also do realistic testing of the model in a vehicular setting. This would provide the most realistic
testing results, but would require a test setup where the thermal camera can be safely positioned outside
of the test vehicle. An additional challenge is where to find reindeer for testing purposes while driving,
as they tend to appear only at times when you would wish they did not.</p>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusions</title>
      <p>In this paper, we presented a CNN model that utilised thermal images to identify reindeer and
diferentiate them from other pedestrians, specifically people. The aim was to create a system that, in the future,
could be integrated into a driver warning system or into an autonomous vehicle’s control systems
to avoid reindeer-vehicle collisions. The model was trained on an open-source dataset and tested on
the self-sourced one, and vice versa, as well as trained and tested on a mixed dataset. The evaluation
shows good comparison against and, at times, exceeds the evaluation metrics of previous research.
The best accuracy of 0.998 was a promising result for reindeer identification from thermal images.
Most importantly, we can showcase that thermal imaging is equally accurate to standard camera-based
methods when it comes to the identification of reindeer. However, typical cameras do not perform well
on dark nights, and our solution with thermal imaging overcomes this restriction.</p>
    </sec>
    <sec id="sec-7">
      <title>Acknowledgments</title>
      <p>The work has been supported by the EU HORIZON projects CHIPS-JU CIA FEDERATE (grant 101139749)
and CHIPS-JU RIA HAL4SDV (grant 101139789), Business Finland HAL4SDV national funding (grant
7655/31/2023), and the Finnish Research Council project Northern Utility Vehicle Laboratory Consortium
GO!-RI (grant 352726). The authors are thankful to Ranua Resort.</p>
    </sec>
    <sec id="sec-8">
      <title>Declaration on Generative AI</title>
      <p>The authors have not employed any Generative AI tools.
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