This website introduces my research accomplishments as well as current research items. Most of the works was done while I was doing my Ph.D at KAIST (~'20.02) under the supervision of Prof. Yoonjin Yoon. I currently work at Smart City Transport Research Center at Korea Transport Institute (KOTI) as an associate research fellow, and my research interests include:

Traffic flow management for high-density Urban Air Mobility (UAM) operation
Urban airspace availability assessment

Please feel free to contact me for any inquiries!

Current work and future direction

Traffic flow management for high-density UAM operation

In urban areas where UAM demand is expected to be concentrated, the risk of contact between aircraft can frequently be at the highest level. To minimize such risk, there needs strategic planning to redirect traffic to lower-density or less-congested airspace while not sacrificing too much extra flight costs.

This working paper proposes a new approach that keeps traffic density levels in urban airspace below the desired threshold while minimizing the total distance traveled by all aircraft. The solver will allocate a sequence of airspace volumes that each aircraft can reserve and use to avoid congested regions.

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UAM demand scenario generation using mobility data

In the near future, urban airspace will be congested with drones due to the demand for faster delivery of food and parcels. The extent to which airspace will be most utilized is uncertain at this point, and will vary from time to time and from region to region. Identifying potential congested areas as well as reducing congestion levels will be one of the critical functions of traffic management for future air mobility.

This research in progress utilizes mobility data to generate a hypothetical demand scenario in which existing food and parcel delivery by land vehicle are partially replaced by aerial services.

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Research accomplishments

Urban airspace availability assessment (below 150 m)

Urban airspace is an important space where many value-creating aerial activities such as drone delivery may take place. However, not all vacant parts of urban airspace are available, since some areas may be blocked from use either temporally or permanently, in order to minimize risks to people, infrastructure, and other air users.

This research aims to find available airspace where aerial vehicles can navigate within an acceptable level of risk, utilizing high-resolution building and terrain data. Specifically, the change in the amount of available airspace was analyzed with respect to geofence parameters in the case study area.

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Related publication

Cho, J., & Yoon, Y. (2018). How to assess the capacity of urban airspace: A topological approach using keep-in and keep-out geofence. Transportation Research Part C: Emerging Technologies, 92, 137-149. IF: 6.077 [pdf]
Cho, J., & Yoon, Y. (2018). Assessing the airspace availability for sUAV operations in urban environments: A topological approach using keep-in and keep-out geofence", International Conference on Research in Air Transportation 2018 Doctoral Symposium (ICRAT 2018). [pdf]

Urban airspace availability assessment (below 1500 m)

The airspace to be used by UAM aircraft is already occupied by various airspace constructs, such as arrival and departure procedures, special use airspace, and temporary flight restrictions. UAM operators should be aware of which airspace is accessible at each altitude, in order to derive safe and efficient route options.

This study aimed to find available airspace that UAM aircraft can access in four ATC integration scenarios. This study highlights that not only the amount but also the shape of available airspace depends on the types of airspace constructs to be considered, the altitude to fly at, and the amount of required separation.

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Related publication

Vascik, P. D., Cho, J., Bulusu, V., & Polishchuk, V. (2019) A Geometric Approach Towards Airspace Assessment for Emerging Operations, ATM Seminar 2019. [pdf]
Vascik, P. D., Cho, J., Bulusu, V., & Polishchuk, V. (2020). Geometric Approach Towards Airspace Assessment for Emerging Operations. Journal of Air Transportation, 1-10. [pdf]

Fast and robust path enumeration in 3D

In an obstacle-rich environment like UTM or UAM airspace, there needs a fast and robust method that can generate route candidates for aerial vehicles moving from one location to another.

This research proposes the use of a two-layered graph structure for fast and robust single-agent pathfinding in a large-scale 3D environment. The first-layer graph encodes the vertical connectivity of airspace based on the topological concept of Reeb graph, whereas the second-layer graph encodes the lateral connectivity of airspace using the medial axis transformation.

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Related publication

Cho, J. (2020). Urban airspace availability assessment framework and its applications using geometric and topological algorithms (doctoral dissertation, chapter 3&4). Korea Advanced Institute of Science and Technology. [pdf]
Cho, J., & Yoon, Y. (2019). Extraction and Interpretation of Geometrical and Topological Properties of Urban Airspace for UAS Operations, ATM Seminar 2019. [pdf]

Modelling airspace as a compact graph structure

Urban airspace is a unique environment where highly obstructed (complex topology) and sparsely structured (simple topology) regions coexist. The presence of static obstacles and the required separation from those obstacles creates particular spatial structures - narrow passages, islands, and funnels - throughout the airspace.

This study proposes a computational geometric approach to model urban airspace as a compact and informative graph structure that summarizes spatial connectivity in the horizontal and vertical dimension. A compact abstraction of airspace into a graph structure provides a basis for density-aware flight planning in urban airspace.

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Related publication
Cho, J., & Yoon, Y. (2021). Extracting the topology of urban airspace through graph abstraction. Transportation Research Part C: Emerging Technologies, 127, 103116. [link]

Cho, J., & Yoon, Y. (2020). Segmentation of Low-altitude Airspace in Highly Constrained Environments, International Conference on Research in Air Transportation (ICRAT 2020). [pdf]