Using the Decision Ladder to understand human decision-making processes
during a UAV-equipped SAR mission
Authors: Hart Sophie , Steane Victoria , Chattington Mark , Bullock Seth , Noyes Jan 
Published: July 2023

The uptake of Uncrewed Aerial Vehicles (UAVs) within the Search and
Rescue (SAR) application is becoming ubiquitous owing to the way in which
UAVs can support and extend SAR responses. During a SAR mission, UAVs are
deployed to offer a birds-eye perspective of the search space which is
captured by the onboard payload sensors and transmitted to human operators
in real time. Currently, this data stream is processed manually by a Payload
Operator to identify any hazards or signs of human life on the ground.
However, the task of identifying and extrapolating information using the
display technology is highly challenging. This is primarily due to the high
levels of cognitive effort which must be expended over time to detect
sightings that are likely to be camouflaged or obscured by the surrounding
terrain. For this reason, system engineers are looking to develop image
classification modules capable of autonomous object detection and labelling
to streamline the information acquisition process from the UAV. When looking
to introduce novel functionality, such as an image classification module, it
is important to consider how decision-making processes are currently
undertaken by the team of human operators. In doing so, a greater
understanding is yielded on how the current ways of working could be
supported through further design intervention. The current work aims to
capture these processes using the representational medium of the Decision
Ladder. Rasmussen (1974) developed the Decision Ladder to define the
different information processing activities undertaken by a decision-maker
when identifying an appropriate course of action within a given situation.
In order to develop the Decision Ladder for the UAV-equipped SAR scenario,
knowledge elicitation activities were conducted using interviews with SAR
personnel.The final amalgamated Decision Ladder was populated using the
responses from the interviews. The decision model demonstrated the
complexity of utilising UAVs to support a SAR mission due to the regulatory
and technological constraints associated with the UAV. In addition, the
importance of a validation activity was emphasised by the SAR personnel
which would be conducted to determine the accuracy of any information
presented by the automated system. Here, the decision ladder was able to
identify the broad set of information aspects that would be reviewed by the
human-UAV team. The subsequent knowledge obtained would be used to identify
the relevance of a sighting and determine the most appropriate response
using the limited resources available within the SAR environment. This
insight provided from the Decision Ladder was used to propose a set of novel
design recommendations that could extend the capabilities of the image
classification module within the SAR context. Therefore, this work advocates
the use of a user-centred design approach to support the development of
technologies based on the tasks and cognitive processes of the end-user.