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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>An Interactive Dashboard for Traveler Mobility Analysis</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Lukas Vorwerk</string-name>
          <email>lukas.vorwerk@tum.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Linus W. Dietz</string-name>
          <email>linus.dietz@tum.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Department of Informatics, Technical University of Munich</institution>
          ,
          <addr-line>Garching</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2021</year>
      </pub-date>
      <fpage>13</fpage>
      <lpage>15</lpage>
      <abstract>
        <p>Showcasing research in data mining is a challenging topic. Developed models of everyday phenomena are often only understandable by domain experts which might lead to low general adoption. We demonstrate an interactive dashboard to visualize the complex domain of international travel over time. Given that spatio-temporal phenomena such as mobility can not efectively visualized using consumer software, we developed a web-based system, where users can explore how the behavior of international and domestic travelers changes over time and easily create their own analyses.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>INTRODUCTION AND RELATED WORK</title>
      <p>
        Human mobility analysis is a widely researched topic with many
facets such as next location prediction [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ], discovering recurring
activity patterns [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], determining diferent traveler types [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], or
deriving touristic travel regions [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. An important problem of all
research eforts concerning human mobility is the visualization of
the results. To establish an understanding of the resulting
models, visualizations are oftentimes very selectively included into the
manuscripts as plots. This, however, only shows a part of the
findings and it is hard for practitioners in the tourism industry to utilize
the academic findings to improve their services. To improve upon
this, we have developed an interactive traveler mobility dashboard
that visualizes patterns of global mobility. The implementation as a
web application ofers users the flexibility to create their very own
analyses.
      </p>
      <p>
        The underlying data stems from a self-collected data set from
Twitter. Due to that most content of Twitter is available for the
general public, it has been frequently used as a source for
researching human mobility [
        <xref ref-type="bibr" rid="ref5 ref6">5, 6</xref>
        ]. We employed our earlier
approaches to mine trips from geotagged tweets [
        <xref ref-type="bibr" rid="ref1 ref3">1, 3</xref>
        ] and
aggregate the metrics into an interactive dashboard available at http:
//mobility-dashboard.cm.in.tum.de.
      </p>
      <p>Dashboards provide users with a customizable overview about
the state of a system without requiring them to work with the raw
data and using programming techniques. Thus, they are an ideal
tool for the general public to explore complex topics such as stock
markets, misinformation on social media1 or global pandemics2.</p>
      <p>
        In this position paper, we present our initial prototype for a
traveler mobility dashboard based on mobility data derived from
social media. We present the motivations and design considerations
to build a dashboard that can visualize analyses concerning trends
1http://csmr.umich.edu/projects/ify-quotient/ [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]
2https://coronavirus.jhu.edu/map.html
in global traveling behavior and point out relevant use cases and
applications.
2
      </p>
    </sec>
    <sec id="sec-2">
      <title>TWITTER MOBILITY DATA SET</title>
      <p>
        Mobility data about individuals is valuable, since it can be used for
many purposes and it is quite complicated to collect it on a larger
scale. Most data sets are limited to national boundaries, since
traditional methods of collection, such as mobile phone communication
records [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] or national statistics are tied to the respective
administrative regions. With the increasing adoption of online location-based
social networks (LBSNs), mobility traces of humans have become
more widely available and this data has the advantage that it is
typically not impeded by traveling to foreign countries. Twitter
is especially useful for researchers, since the service is inherently
public and it provides oficial APIs to query user timelines.
      </p>
      <p>Whenever a user tweets with the geolocation option enabled,
her approximate location is attached to the message. The downside
of LBSN mobility data is that it gives an incomplete picture of the
user’s mobility — the location is only known when she decides to
tweet. This makes it necessary to assess the quality of the data with
respect to the use case, eventually, discarding trips of insuficient
data quality.</p>
      <p>Feature
Tweets with geolocation
Users
International Travelers
Domestic Travelers
Trips
International Trips
Domestic Trips
Countries visited
Observation period</p>
      <p>Value</p>
      <p>Since 2018, we collected timelines of Twitter users and using the
Python tripmining library3, we segment geolocated tweets of a
user’s timeline into periods of being at home and on travel. If a user
tweets at a relatively constant pace, this data can be quite reliable,
which is also one of the of the library’s features to assess using
various metrics.</p>
      <p>Table 1 summarizes the statistics of our Twitter trips data set
used for the dashboard. As the data collection is ongoing, these
3https://github.com/LinusDietz/tripmining
Lukas Vorwerk and Linus W. Dietz
specific chart areas. To the best of our knowledge, this platform is
the first ofering an interactive analysis of global travel trends.
numbers are constantly growing. While only parts of the data set
are currently publicly available4, we are able to provide mobility
data to interested researchers on a trip-level.
3</p>
    </sec>
    <sec id="sec-3">
      <title>MOBILITY DASHBOARD</title>
      <p>The dashboard consists of three interactive visualizations that invite
users to engage with the data and create mobility analyses on their
own. The central feature is a choropleth world map that reflects the
number of inbound or outbound trips on a country-level basis. The
exact number is shown when hovering over the respective area on
the map. By using a toggle switch, the user can decide whether to
display inbound or outbound trips. Upon clicking on the area of
a specific country, users are presented with a detailed analysis of
this country. They can now determine where the residents of this
country prefer to travel to and from which other countries travelers
visit this country in which quantities. Figure 1 shows the number
of outbound trips in our database undertaken since 2015.</p>
      <p>Besides the map, a list containing the top ten countries for the
selected scenario is displayed. An additional visualization in the
form of a line chart displays the mean and median trip duration per
year or month. To provide insights into the data the visualizations
are based on, the dashboard also includes the statistics shown in
Table 1 and a chart that indicates the number of trips per year or
month (see Figure 2). Furthermore, a time slider ofers the possibility
to uncover temporal trends over the last decade. All of the described
dashboard elements are interconnected, i.e., if the user selects a
specific country or year, all visualizations are updated accordingly.</p>
      <p>
        The dashboard is developed using Dash5, a “Python framework
for building web analytic applications”. The usage of Dash enables
further interactions with the visualizations such as zooming in on
4https://github.com/LinusDietz/JITT2020-Mining-Trips-Replication [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]
5https://dash.plotly.com/introduction
      </p>
    </sec>
    <sec id="sec-4">
      <title>LIMITATIONS AND USE CASES</title>
      <p>Given the intrinsic properties of the data, some analyses work better
than others using the dashboard. What works quite well is to get an
indication of the popularity of a destination country as well as the
popular travel seasons aggregated on a monthly basis. Certainly, the
raw numbers have little meaning, since they only account for the
mobility of Twitter users. The relative popularity of countries in the
Western World, however, should be meaningful. On the contrary,
the numbers for countries where Twitter is not much adopted, e.g.,
due to state censorship, are certainly not representative.
Furthermore, the overall amount of data might be enormous (cf. Table 1),
but when subdividing it into 7 years (currently about 73 months),
241 countries, and inbound and outbound trips, the amount of data
points can become quite low, especially for small countries. Finally,
it should be noted that the data collection is slower than its creation,
and it takes time until enough recent trips are collected. For this
reason, the most recent data is the most incomplete, since trips that
are currently occurring can not yet be included in the data set.</p>
      <p>Therefore, the target audience of the dashboard is rather the
general public than researchers. The number of possible analyses is
intentionally limited at the moment, since we believe that increasing
complexity would hinder layman to interact with the dashboard to
produce their own simple, but useful analyses.
5</p>
    </sec>
    <sec id="sec-5">
      <title>CONCLUSIONS AND FUTURE WORK</title>
      <p>This paper described the interactive visualization of international
traveler mobility from Twitter. The underlying data has been
collected over the last year and shows the high value of LBSN data
for such analyses. With the presented dashboard, we provide a tool
that can be used to perform own analyses on the complex domain
of international travel. Currently, the dashboard allows to explore
the temporal variability of the number of inbound and outbound
trips of Twitter users.</p>
      <p>
        In the future, we plan to improve the granularity of the analysis
into smaller regions, such as federal states or touristic regions [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ].
Furthermore, it should be possible to set the timeframe to custom
dates, to be able to observe seasonal trends e.g., introduced by school
breaks or holidays associated with traveling, such as Thanksgiving
in America. Finally, we plan to develop further analyses, e.g., to
reveal which countries have often been traveled to together.
      </p>
    </sec>
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