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Redesigning the User Interface for
the Micro-Air Vehicle Project
This paper describes the redesign of a user interface for unmanned
air vehicles tasked with a reconnaissance task. Based on subject matter
expert’s feedback, it was determined that while the current interface
indeed contained all the information, the presentation and aggregation
of the data could be improved. In particular, we decided to focus on the
issue of having a decision support system for having a second relief
aircraft launched timely in order to provide close to un-interrupted
operational coverage.
1
Introduction
Unmanned Aerial Vehicles (UAVs) are increasingly being deployed by both military and civilian users
to work in environments and situations in which it is not desirable to place a human. UAVs offer many
advantages, such as lower cost (compared to human-operated aircraft), reducing the risk to humans,
and flexibility in terms of operating in conditions unpalatable to humans, such as areas affected by the
release of toxic material. UAVs can also be made much smaller and lighter than manned vehicles (e.g.
Micro Air Vehicles or MAVs) and are thus suitable to reconnaissance missions.
The 1st US-Asian Demonstration and Assessment of Micro Air and Unmanned Ground Vehicle
Technology was organized in Agra, India from March 10 to March 15 2008 to provide potential endusers of MAV systems with a clear picture of the current state-of-the-art of the technology. Participants
in the competition had to use their MAVs to accomplish a specified mission. One of the entries was a
group from MIT and Ascending Technologies, led by Prof. Nicholas Roy. This team employed
autonomous micro-quadrotor helicopters with hover capability to perform the mission. The goal of this
project was to design an interface that would allow the team to interact with the quadrotors.
In section 2 of this report, we introduce the mission scenario. In section 3, we show the cognitive
task analysis that was performed prior to designing the display. Section 4 presents the initial design,
section 5 the results of testing the interface with human test users, and section 6 the updated design
based on feedback obtained from the test users.
2
Mission Overview
The mission scenario is that an armed and hostile group has taken several innocent civilians hostage
in a bank building. Commandos (Special Forces) have been tasked with freeing the hostages. However, it
is known that the area around the bank building has been mined, with the locations of the mines
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unknown. Also, a hostile guard vehicle patrols the area around the bank building with a known and
predictable timeline.
3
Cognitive Task Analysis
A cognitive task analysis was performed based on multiple interviews with subject matter experts
(SMEs). First, the mission was divided into three broad roles:
1. Performing the actual mission (find landmines, spot guard vehicle, guide the
commandos
2. Monitoring and maintaining the active UAV (the vehicle currently involved in performing
the mission)
3. Managing the backup UAV and the exchange between the two.
The first role was further subdivided into the tasks of searching for landmines and the guard vehicle,
and guiding the commandos. Searching for landmines and the guard vehicle involve observing the video
images being returned by the onboard camera and carefully observing them. Also, once a landmine or a
guard vehicle has been observed, its location on the image needs to be tagged by the human operator.
However, to be able to effectively gather information, the camera operator also needs to have low-level
control over the UAV to be able to redirect it to an interesting location. The task of guiding the
commandos involves taking the information about the mine and guard vehicle locations and using it to
create a path for the commandos to follow. The task also includes warning the commandos if they
appear to be in danger of being detected or running into a mine.
The second role (monitoring and maintaining the UAV) involves planning a path for the active UAV
to follow, and monitoring its health (battery status, GPS quality). Planning a path involves creating
waypoints for the UAV to follow and monitoring the actual position of the UAV, while health monitoring
requires the user to be aware of the battery voltage level and accuracy of the GPS.
The third role (monitoring the second UAV and handling the exchange between the UAVs) primarily
requires the user to be aware of the health status of both UAVs. Path planning for the second UAV is
also included as a subtask, but this UAV’s specific path is less important since it is not performing the
actual mission. The most important subtask is to decide when to launch the second UAV and have it take
over as the active UAV. This task is important because efficient switching between UAVs minimizes the
time lost during the mission. Also, since this task involves coordinating multiple UAVs, it is very
cognitively demanding.
The different tasks that need to be accomplished for mission success into 4 different operator roles:
1. Camera Operator: Monitors the camera image and tags mines and the guard vehicle, and has
the option of exercising low-level control over position and speed of the UAV to explore areas of
interest
2. Ground Coordinator: Keeps track of the locations of mines and the guard vehicle and prepares a
path for the commandos to follow. Also warns the commandos if they are in danger of
encountering a mine or being detected by the guard vehicle.
3. Planner: Prepares paths for the active UAV to follow and monitors its health.
4. Supervisor: Monitors the health of the both the active and incoming UAV, and ensures that the
incoming UAV takes over from the active UAV in time to ensure constant coverage. Also plans
the path for the incoming UAV if necessary.
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This division of tasks and roles between operators is shown in the Cognitive Task Analysis diagram
below (Figure 1).
Depending on the operational tempo, it is conceivable that a single operator could fill in two distinct
roles. For instance, in times of low workload, the UAV planner could also monitor the ground vehicles
and the commandos, since the UAV is autonomous and can follow the prepared path without constant
human intervention. Also, the camera operator could him/herself launch the incoming UAV since the
incoming UAV, once told to launch and reach a particular location, does not need to be constantly
monitored.
Figure 1: Cognitive Task Analysis
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Initial Design
Based on the results of the CTA, we first produced a pen and paper design that satisfied the
information requirement derived in the previous phase of the design. We then showed the results of our
paper mock-up to one of our SMEs. This provided additional feedback which we incorporated in our
initial implementation of the interface. We decided to implement a separate interface for each of the
roles we identified in the CTA, but we also strived for consistency between interfaces by having critical
information presented in the same format and at the same place across all interface. We present the
different interfaces in this section.
4.1
Basic Screen Layout
Figure 2: Common Design Elements
Figure 2 shows the basic layout that is common to all interfaces. At the very top are the tabs that
allow each member of the team to easily access the interface for all different roles. This is useful since
all team members may need to help each other out should one of them become overworked. In the
main window, most of the space is allocated to the Primary Screen. Each role has a different primary
screen – as will be seen later, the Camera Operator’s primary screen shows the video image from the
camera on the quad-rotor, the Planner’s primary screen shows an annotated map of the area, and so
on. At the top right corner is the Secondary Screen, which provides information that might be useful for
a task but not essential. The secondary screen is mostly provided to promote situational awareness. For
example, the secondary screen for the Planner would be the camera image, while that of the camera
operator would be the map. The Control Panel provides tools for the operator to manipulate the
particular hardware or software that he/she uses. For instance, for the Camera Operator, the control
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panel contains controls to adjust the camera viewing angle. Similarly, for the Supervisor, the control
panel includes buttons to launch a new UAV or bring the current UAV back to home base. The last item
of the upper portion of the interface is the Mission Time, which is always present on the screen.
The lower portion of the screen contains critical information that is available to all roles at all times.
The Time Bar (see Figure 3) keeps track of which part of the mission timeline is currently being
executed, and also shows which tasks have just been completed and which tasks are up next. The time
bar is automatically updated when the plan is changed, and the plan can also be changed from the
taskbar. The timeline also indicates temporal projections such as low battery or guard vehicle
waypoints.
Figure 3: Mission Time Bar
Below the time bar is a plan control interface modeled after the usual Pause/Play/Forward/Stop
paradigm (see Figure 4). The pause button allows plan to proceed until the next item. The play button
allows resuming whatever action was interrupted. The fast-forward control allows skipping to the end of
a plan item. Finally, the stop button halts the MAV immediately (as opposed to the Pause button which
halts the MAV at the end of the current planning period).
Figure 4: Plan Control Interface
The Status Bar (Figure 5) keeps track of essential information such as the quality of the GPS, the
Altitude, and the Battery level. The altitude indicator displays the current altitude and also displays
swinging arm indicating the rate of ascent or descent.
Figure 5: Status Bar
Figure 6: Task List
The Task List (Figure 6) essentially is a computerized version of the playbook. The task list displays
the task currently being executed and the name of the person executing the task, and also shows the
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tasks that precede and succeed the current task. Team members can check off tasks as the mission
progresses. The task list, however, is not linked to any other part of the interface and only serves as a
reminder: departures from the playbook are therefore not considered here.
4.2
Camera Operator Role
Supervisor
Active
Planner
Incoming
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90
45
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Mission
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Hover
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t+3mn
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Plan Control
t+5mn
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t+6mn
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2
10
Phase
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Sam:
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RJ: Edit
Obstacles
x
x
RJ:
!
3
BAT
6mn00s
Bat
GPS
4
Commando Plan
Abe: Cam
off
x
Figure 7: Camera Operator Display
The basic role of the operator is to use the video image provided by a camera on board the quadrotor to look for mines, guards and hostages. In order to do so successfully, the camera operator
requires the ability to control the orientation of the camera. Furthermore, the camera operator might
also need to manually override the automated plan and manually fly the MAV. This could happen when
a mine is detected right on the edge of the field of the view of the camera and the MAV needs to get
closer in order to positively identify the threat. It is assumed that the camera will be mounted on a
gimbaled platform such that the camera view remains constant unless changed by the Camera Operator
(i.e. disturbances in the motion of the UAV will be actively compensated for).
A slider in the control panel allows the camera operator to adjust
the camera angle from straight down to horizontal. There are also three
fixed angle settings (0 deg, 45 deg and 90 deg) that the operator can go
to by just clicking on the appropriate button. It was determined during
the interviews with the SMEs that the 45 deg position would be
commonly used in most flight phases while the 0 degree (straight
down) is convenient to locate mines or landmarks directly below the
MAV. Finally, the 90 deg preset is useful for looking for hostages. The
camera can also be controlled by using the drag-and-drop metaphor
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(googlemap-like) on the video screen. Moving the camera does not stop the plan.
On the video feed itself, the center of the video is indicated by a
bulls-eye display. The camera operator can move the vehicle manually in
a certain direction by using the arrow keys on his/her keyboard. The
“up” arrow would move the UAV in the direction the camera is pointed
in, the “down” arrow would move it in the opposite direction, and the
left and right arrows would make it slide left or right, respectively. Two
other keys are used to control altitude (see Figure 9). Whenever the
operator takes manual control of the MAV, the mission pauses
automatically. The operator can thus move the vehicle manually if
he/she feels the need to go off the planned path to observe certain
features more carefully. The Camera Operator can tag a land mine
Figure 9: Keyboard Control Scheme (WASD)
on the camera image by simply right-clicking on the appropriate
location on the image. The interface then asks the operator to confirm whether to tag that location as a
mine or not. Guard vehicles can be tagged in a similar fashion. Clicking on a tagged guard vehicle brings
the option of switching into guard tracking mode. In this mode, the MAV will automatically follow the
guard vehicle. The current mission is therefore put on hold. The predefined mission plan can be
resumed by pressing the “Play” button on the plan control interface.
Other features that appear on the camera operator’s interface are locations of the waypoints
superimposed on the main camera image. In addition, a green arrow acts as an indicator for both
velocity (magnitude of the arrow) and direction (angle of the arrow). In the secondary screen, the
camera operator can also see a map of the area annotated with the waypoints and planned routes of
the UAV, as well as the current position of the guard vehicle. The area that is within view of the guard
vehicle is also indicated to enable the camera operator to avoid being sighted while hand-flying. Also
superimposed on the time bar is the expected timeline of the guard vehicle and the time when the UAV
could potentially be spotted by the guard vehicle.
The “Incoming” tab on the interface is the exact same interface at the “Active” interface described
in this section, except that the video feed and controls are linked to the secondary UAV as opposed to
the active one. This allows the supervisor to have visual confirmation that the relief UAV is still on track.
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Planner
Planner
Supervisor
Active
Incoming
WP
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Altitude 10 m
Altitude
Hover 3 min
Speed
Altitude 20 m
Hover
Hostage
X
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!
H
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Task
3
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Hover 3 min
X
Demine
Alt 35m
Take Off
X
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t-1mn
Active
t
WP-3
B
t+1mn
Hover
t+2mn
t+3mn
t+4mn
WP-4 Alt 35m
C
t+5mn
WP-5
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Go Home
Hover 2mn
20
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1
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2
Sam:
Verify GPS
RJ: Edit
Obstacles
x
x
RJ:
!
3
BAT
6mn00s
Plan Control
Phase
2
Bat
GPS
4
Commando Plan
Abe: Cam
off
x
Figure 10: Planner Display
The basic role of the Planner is to create safe paths for the UAVs to go from home base to the bank
building. In addition, the UAVs should detect and tag mines and guards vehicle(s) that could threaten
the commando units. The path should also be designed in order to minimize the chances that a UAV
could be detected by a guard unit. Each path is characterized as a sequence of waypoints through which
the UAV must pass. At each waypoint, one or more task can be added, such as hovering for a fixed
period of time at a certain altitude, finding mines, locate hostages, etc.
The primary screen for the Planner is a map of the area. The map prominently shows the bank
building and home base, as well as major fixed features such as roads and water bodies. Also shown on
the map are waypoints that have already been created by the Planner, and straight-line paths between
the waypoints that the UAV should follow. The actual location of the UAV and its current direction of
motion are also shown. The map also shows the (estimated) location and the field of view of the guard
vehicle. Finally, the display also shows the location and path of the secondary UAV, either incoming or
outgoing.
The secondary screen and the control panel are both replaced by a planning tool which allows the
Planner to add and modify waypoints. A list of waypoints and the tasks to be executed at that waypoint
are shown. The order in which the waypoints are executed can also be edited by dragging waypoints up
and down the list. The waypoint currently being executed is highlighted. When a waypoint is added, the
planner can pick from a list of tasks shown at the far right of the screen and assign that task to that
waypoint.
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Supervisor Role
Supervisor
Planner
Active
Incoming
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D
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4
A
D
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Secondary Screen
BB
C
C
B
2
B
H
Incoming UAV
Primary Screen
10
Launch
!
1
0m
22mn
Bat
t-1mn
Active
t
WP-3
t+1mn
Swap
-10
A
t+2mn
Hover
t+3mn
t+4mn
WP-4 Alt 35m
B
C
t+5mn
t+6mn
GPS !
20
Phase
1
15.5m
1
10
2
Launch WOO
WP-5
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WP-1
Sam:
Verify GPS
RJ: Edit
Obstacles
x
x
RJ:
8mn00s
Incoming!
Phase
2
Bat
GPS
4
Commando Plan
Abe: Cam
off
x
Figure 11: Supervisor Display
The basic role of the supervisor is to monitor the health of the UAVs and to maximize the probability
of having at least one UAV actively performing the mission at all times. The Supervisor’s primary screen
is the same as the Planner’s primary screen, showing a map of the area annotated with the mission plan.
The supervisor also sees the camera image in the secondary screen. In the control panel, the supervisor
sees the health status of the second UAV (i.e. altitude, battery level and GPS level), and has one button
to launch that UAV and another to perform the “Swap” operation. When the “launch” button is pressed,
a second UAV will take off and approach the location of the first vehicle, potentially following a specific
set of waypoints defined by the supervisor. Once the Supervisor sees that the second UAV is close to the
first, he can press the “Swap” button. The swap operation consists of turning over all the tasks and
waypoints assigned to the currently active UAV over to the incoming relief one. In particular, the swap
operation switches the camera view from the first UAV to the second. Swap also makes the secondary
UAV “active”, i.e. the Camera Operator now has control over the new UAV and this new UAV begins
executing the tasks prepared by the Planner. At the same time, the formerly active UAV then heads back
to the home base in order to recharge its batteries.
At the bottom, in the Time Bar, the Supervisor not only sees the current mission status, but also the
second UAV’s timeline. The mission timeline for the first UAV is the same as for the camera operator.
The timeline for the second UAV shows the “launch window of opportunity”, which is the expected time
during which the second UAV can be launched such that it can take over from the first UAV before the
first UAV risks running out of battery on the way back to the base.
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Ground Operator
Supervisor
Planner
Active
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Ground
Incoming
WP
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A
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Arrive t + 0:30
Depart t + 2:00
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Primary Screen
H
Arrive t – 1:00
Depart t – 0:40
A
BB
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Time
X
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D
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Arrive t + 2:45
Depart t + 3:40
Arrive t + 6:00
Depart t + 8:45
A
Add WP
Phase
1
Hold
Commandos
t-1mn
Ground
Unit
t
WP-B
B
t+1mn
Hold
t+2mn
WP-C
t+3mn
t+4mn
Hold
t+5mn
t+6mn
2
D
Plan Control
Sam:
Verify GPS
RJ: Edit
Obstacles
x
x
RJ:
WP-D
C
1
Phase
2
Assault
3
4
Commando Plan
Abe: Cam
off
x
Figure 12: Ground Operator Display
The basic role of the Ground Operator is to monitor the guard vehicle and create a plan for the
ground troops to travel from home base to the bank building without being detected. The ground
monitor also monitors the state of the mines which may be on the path of the commandos1.
The Ground Operator’s interface is similar to the Planner’s interface, with some differences. First,
the map is annotated with not just the positions and waypoints of the UAV but with those of the ground
troops as well. Also shown is the recent path taken by the guard vehicle, its current position and
heading, and the area that is within sight of the guard vehicle. Thus the Ground Operator can monitor
the position of the ground troops and the guard vehicle simultaneously, and use the large HOLD
COMMANDOS button on the right if he/she sees that the ground troops might be detected. The
“Assault” button indicates that the commandos are out of sight from the guard vehicle and can proceed
to enter the bank building.
The planning tool to the right provides the Ground Operator with the ability to create waypoints and
tasks for the ground troops. The Ground Operator can create arrival times and departures times for each
waypoint, and thus tell the troops exactly where they should be at any given time. The Time Bar at the
bottom shows the mission status of the ground troops, and superimposes on this the current location of
the guard vehicle and prominently marks with a red rectangle those times of the mission when the
ground troops would be within sight of the guard vehicle.
1
For this project, we assume that the mine disposal is automated and does not require human supervision.
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Testing
Once the implementation of the interface was finished, we conducted formal testing in order to
assess the usability of the proposed system. In particular, we used two separate metrics for this
assessment: the first one is the modified Cooper Harper Scale(Cummings, Myers, & Scott, 2006) and the
second one is the 10 heuristics evaluation technique from Nielsen (Nielsen, 1994) . We first ran 3
subjects, thereby obtaining a first round of feedback based on which we performed a design iteration
(described in the next section). We then re-ran the same evaluation protocol with another 3 subject on
the updated interface.
We administered both test to our subjects after a quick walkthrough of the interface. The
walkthrough was divided into two phases. The goal of the first phase of the walkthrough is to familiarize
the subjects with the basic functions and concepts presented in the interface. During the second phase,
we asked the subjects to perform 4 basic tasks in a low fidelity prototype2:
 Waypoint addition and removal (Planner)
 Mine tagging (Active UAV monitoring)
 Launch of the relief UAV and swap (Supervisor)
 Ground monitoring and threat avoidance (Ground Monitor)
These tasks were specifically designed to test the clarity of the different mechanisms and
metaphors used in each of the interfaces. Then, after the completion of the tasks, we presented both
the Modified Cooper Harper Scale and the Nielsen’s heuristic test to the subject.
5.1
Modified Cooper Harper Scale
The Modified Cooper Harper Scale was developed MIT’s Humans and Automation Lab. The aim of
the Modified Cooper Harper Scale is to determine whether a display enables the information gathering
and processing necessary to complete and manage higher-level system tasks (Cummings et al., 2006).
Figure 13 shows the actual metric flowchart presented to the subjects. Note that in this metric, lower
scores denote better interfaces.
2
The low fidelity prototype consisted of Powerpoint slides with animations and hyperlinks.
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Figure 13: Modified Cooper Harper Scale for UAV Operations
The results were overall good, with an average score of 3.33 for the initial interface and 2.66 for the
updated interface. Figure 14 shows box-plots of the results. It is interesting to note that there seems to
be an improvement in the score, which would suggest that the changes we made were indeed beneficial
for interface usability. We did not, however, manage to reach the “display is acceptable” range: this was
probably due to some design sub-optimality, but we also posit that our low-fidelity prototype was not
conducive to conveying all the richness of the potential interactions.
Figure 14: Results of the Modified Cooper Harper Scale: Before and After the Design Iteration
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Heuristic Analysis
Nielsen’s ten usability heuristics were defined as quick rules of thumb that should be followed by any
interface. These heuristics are therefore useful to evaluate our displays.
Nielsen’s 10 Heuristics (Nielsen, 1994)
1. Visibility of system status
2. Match between system and the real world
3. User control and freedom
4. Consistency and standards
5. Error prevention
6. Recognition rather than recall
7. Flexibility and efficiency of use
8. Aesthetic and minimalist design
9. Help users recognize, diagnose, and recover from errors
10. Help and documentation
However, due to the limitations of our interface, we decided to remove questions 9 and 10 from our
test. We collected data by presenting our subjects with a 5-point Likert scale for each of the questions.
For each question, the scale ranged from 1 = very bad to 5 = very good. Thus, contrarily to the Modified
Cooper Harper scale, lower score denote worse interface. The results, in box-plot format, for each
questions is shown in Figure 15. The plain box-plots represent the scores before our redesign and the
hashed ones the scores after the redesign. Generally, we again saw good improvement in usability
evaluation after the interface design iteration. Of interest, we had relatively low score for the user
control and freedom score before the redesign compared to a higher score afterward. Another
interesting point was that our best scored heuristic was “aesthetics and minimalist design”: all 3 subjects
gave us the maximum score of 5 (very good) after the re-design of the interface. However, it must be
noted that we did seem to get lower score after the redesign for the “match between system and the
real world” and “recognition rather than recall” heuristics. While somewhat surprising, these results
could also be due to the small number of subjects we tested in the pre- and post-redesign conditions3.
3
We had 3 subjects per condition.
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Figure 15: Result of for the Nielsen's 10 Heuristics
6
Changes from the Initial Design
There were a few changes made after the first usability test based on the feedback received. First,
we had observed that some users were confused (or were delayed) by the need to create a waypoint on
the map, and then having to go to the right edge of the screen to create a task for that waypoint. Based
on this observation as well as direct feedback, we modified the design so that a drop-down menu with
the list of tasks appears on the map upon right-clicking to create a waypoint. Thus users no longer have
to go to different parts of the screen to create waypoints and allocate tasks to that waypoint.
A second improvement was in the timeline scrolling. Initially, the yellow bar indicating current time
scrolled from left to right across the timeline bar. However, it was noted by some subjects that it was
too easy to overlook the time bar. Thus the design was changed so that the current time indicator
stayed fixed, while the entire time bar scrolled from right to left. The constant motion of the time bar
was intended to naturally draw users’ attention to it.
A third improvement was in the Supervisor screen. One subject noted that the supervisor’s role
after deciding to launch the UAV involved very little participation, and only required monitoring. Thus it
was easy to stop paying attention. The subject suggested adding a notification, perhaps even
automating, the actual swap between the UAVs once the incoming UAV came within close proximity of
the active one. Both these suggestions were incorporated – “Swap” was added to the list of tasks that a
user could assign to a waypoint. Once reaching that waypoint, the “Swap” button on the supervisor
screen would be highlighted to indicate that the UAVs were ready to swap roles.
A final improvement was in the Ground Coordinator screen. Once the commandos are “held” by
clicking on the “Hold Commandos” button, the lettering on the button changes to “Release
Commandos” to ensure that the user stays aware that the commandos have been told to hold.
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Conclusion
In summary, the user interface for the MAV mission was undertaken by first conducting a Cognitive
Task Analysis (CTA), following which the major tasks were identified and grouped into four different
roles that an operator could take – a Camera Operator, Planner, Ground Coordinator and Supervisor.
Each of these operator roles has its own specific screen, with some crucial information (such as UAV
health and locations of the mines and guard vehicle) shared across all screens. A preliminary usability
study pointed to several features that could be improved, and these changes were carried out. A second
usability study conducted after the changes were made showed an improvement in the users’ rating of
the display.
Some new features could be incorporated in future designs. One of these would be a “Synchronize”
button to synchronize the actual position of the guard vehicle with the interface’s estimate of where it
should be. This would ensure that large errors do not accumulate in the position of the guard vehicle.
Thus further improvements could be made to the design presented, particularly if the mission
specifications change. Nevertheless, the usability studies have shown that the interface is an effective
tool through which operators can perform the specified mission.
8
References
Cummings, M. L., Myers, K., & Scott, S. D. (2006). Modified Cooper Harper Evaluation Tool for Unmanned Vehicle Displays.
Paper presented at the UVS Canada Conference.
Nielsen, J. (1994). Heuristic evaluation. In J. Nielsen & R. L. Mack (Eds.), Usability Inspection Methods. New York: John Wiley &
Sons.
Yves Boussemart
Aditya Undurti
15
16.422
9
Final Project Report
14-May-08
Appendices
pre
post
Valid N
(listwise)
N
Mini
mum
Maxi
mum
3
2.00
5.00
3
2.00
4.00
3
Std.
Mean Deviation
3.333
1.52753
2.666
7
1.15470
3
Table 1: Modified Cooper Harper Scale Raw Results
Maximu
N
Minimum m
Mean
Std. Deviation
vis
6
4.00
5.00
4.5000
.54772
match
6
4.00
5.00
4.1667
.40825
freedom
6
2.00
5.00
3.6667
1.21106
consistency
6
4.00
5.00
4.3333
.51640
error
6
3.00
5.00
4.0000
.89443
recog
6
3.00
5.00
4.1667
.98319
flexibility
6
3.00
4.00
3.6667
.51640
aesthetic
6
4.00
5.00
4.8333
.40825
Valid N (listwise)
6
Table 2: Heuristic Design Results
Yves Boussemart
Aditya Undurti
16