CHI 2007 Proceedings • Mobile Interaction Techniques II
April 28-May 3, 2007 • San Jose, CA, USA
Comparing Physical, Automatic and Manual Map Rotation
for Pedestrian Navigation
Will Seager,
Department of Computer Science,
University College London,
London WC1E6BT. UK.
[email protected]
Danae Stanton Fraser,
Department of Psychology,
University of Bath,
Bath BA27AY. UK.
[email protected]
ABSTRACT
journey times, missed appointments and frustration during
travel.
It is well-established finding that people find maps easier to
use when they are aligned so that “up” on the map
corresponds to the user’s forward direction. With mapbased applications on handheld mobile devices, this
forward/up correspondence can be maintained in several
ways: the device can be physically rotated within the user’s
hands or the user can manually operate buttons to digitally
rotate the map; alternatively, the map can be rotated
automatically using data from an electronic compass. This
paper examines all three options. In a field experiment,
each method is compared against a baseline north-up
condition. The study provides strong evidence that physical
rotation is the most effective with applications that present
the user with a wider map. The paper concludes with some
suggestions for design improvements.
Another reason why these applications need to be usable is
that they are likely to be integral to most location-based
services. Uptake of these services may partly depend on the
usability of the navigation component of the service. For
example, users are less likely to use a service that locates
the nearest bank if they experience problems finding their
way to the bank.
One important potential usability issue concerns whether
users of these new applications and services are able to
view a map that is aligned with the environment. Research
with static maps and maps that form part of vehicle
navigation systems suggests that maps are easier to use
when “up” on the map is aligned with the user’s forward
direction [e.g. 2, 7, 8, 9, 12]. While this issue has received
some attention within the context of navigation applications
designed for pedestrians, this research has focused on either
turn-by-turn based instructions [6] or else on head-mounted
displays [14]. It has yet to be investigated in relation to the
wider map-based formats that are more typical of the
available commercial products.
Author Keywords
Egocentric maps, mobile computing, automatic rotation
ACM Classification Keywords
H.5.2 Information interfaces and presentation (e.g., HCI):
Interaction styles.
This paper describes an investigation into the issue of map
alignment on handheld mobile devices. In contrast to
previous research, it considers map alignment in relation to
applications that present the user with a wider map. A field
experiment is described in which several methods for
maintaining track-up alignment are compared against a
baseline north-up alignment condition. The experiment
includes measures of task performance, user satisfaction
workload and spatial orientation. The study provides strong
evidence that physical rotation is the most usable way to
maintain track-up alignment with this type of format. The
paper concludes with some suggestions for how designers
can enable physical rotation.
INTRODUCTION
With the emergence of mobile digital technology, new
forms of navigational support have become available to
people wayfinding on-foot within urban environments.
With mobile phone ownership at 2.5 billion [15] and signs
that phone manufacturers are beginning to bundle
navigation applications as standard features [13], there’s
every likelihood that these new navigations will reach a
very wide user base within the near future. With the
potential for such widespread use, poor usability could have
a high social and economic cost in terms of increased
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CHI 2007, April 28–May 3, 2007, San Jose, California, USA.
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BACKGROUND
A number of studies have found that people are able to read
maps more easily when the map is aligned [e.g. 2, 7, 8, 9,
12]. For example, in one experiment, participants were
more successful in navigating to target destinations after
viewing “you-are-here” maps that were aligned with the
environment [7]. This “alignment effect” has been shown to
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CHI 2007 Proceedings • Mobile Interaction Techniques II
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be robust across different types of map stimuli and
experimental task [2, 8, 9, 12].
Another experiment compared two forms of track-up
alignment on a navigation assistant presented via a headmounted display (HMD) [14]. Participants were asked to
navigate using a tethered (i.e. perspective) view of a map
presented on a partially transparent HMD. In one condition,
participants were able to press a button to bring the map
into alignment. In another condition, the map was
automatically maintained in a track-up alignment. No
statistically significant performance differences were found
between the two methods, nor any differences between the
subjective comments. It was concluded that both methods
should be supported in the software.
Generally, poorer performance with misaligned maps is
attributed to mental rotation; that is, it is thought that map
readers must mentally rotate a mental image of the
misaligned map in order to relate the information it contains
to the environment. This theory has received empirical
support from studies that show a near linear relationship
between increasing degrees of misalignment and decreasing
performance on map reading tasks [e.g. 2].
Some research has investigated map alignment within the
context of vehicle navigation systems. Here, the general
approach is to compare two types of display known as
“track-up” and “north-up” maps. With track-up maps, the
map is maintained in alignment through rotation i.e.
whenever the vehicle changes direction, the map rotates so
that the forward/up correspondence is maintained. North-up
maps remain in a static orientation with north at the top as
the user moves through the environment (they are aligned
when the user is heading north, but for all other directions,
they are misaligned). The general finding of this research is
that users perform better on most navigational tasks when
using track-up maps [e.g. 1, 16]. However, in one study,
participants performed better in a map reconstruction task
following navigation with a north-up map. It was concluded
that spatial orientation and cognitive map formation
benefits from the stable orientation provided by a north-up
map [1].
Finally, one group of researchers reported a planned
comparison between north-up and track-up alignment on a
mobile device [17]. They intend to vary the centre of
rotation, predicting that users will prefer the centre of
rotation to be closer to the bottom end of the screen rather
than centred in the middle of the screen.
The issue of map alignment has yet to be investigated in
relation to navigation assistants that present the user with a
wider map. This map-based format has been used in some
research prototypes [e.g. 3] and many current commercial
navigation products designed for pedestrians. While it’s
likely that turn-by-turn systems will become more widely
used in the future, there’s every reason to think that the
map-based format will endure. Maps have a number of
advantages: they provide the user with additional
information ahead of time and help the user to stay
orientated to familiar locations (e.g. earlier points on their
current route or locations they have visited on previous
trips). They are better at supporting sudden changes of
travel plan or opportunistic detours and are thus better
suited to leisure-based travel. Furthermore, turn-by-turn
systems depend on accurate and reliable positioning
information to trigger the timely display of new turn
presentations. While systems like Galileo are set to improve
the accuracy of the Global Positioning System (GPS), poor
reliability caused by tall buildings and other factors may
ultimately limit the usability of turn-by-turn based formats
designed for pedestrians.
In recent years, the topic of map alignment has received
some attention from researchers interested in digital
navigation assistants for pedestrians. Several papers have
suggested that track-up alignment on a handheld mobile
device could be maintained through automatic rotation
using data from an electronic compass [4, 6, 10, 17]. Some
have theorized that automatic rotation would reduce the
cognitive overload associated with physical rotation of the
device [6, 10].
In a field experiment, Hermann, Bieber, and Duesterhoeft
compared automatic map rotation with physical rotation
and a north-up condition [6]. Participants were asked to
navigate a short indoor route using a non-functional
prototype operated by the experimenter. In each case, they
were presented with a series of two-dimensional plan-views
of single turns. In one condition, they were required to
physically rotate the device so that the turn was aligned
with the environment. In a second condition, they were
required to hold the device in a fixed orientation with north
to the top of the map. A third condition simulated automatic
rotation. Participants were able to navigate more
successfully (i.e. more quickly and with fewer errors) in the
automatic condition followed by the physical rotation
condition. The authors suggested that automatic rotation
reduced mental workload allowing participants to pay more
attention to other aspects of the navigation task.
FIELD EXPERIMENT
The goal of the experiment was to examine three different
methods for maintaining track-up alignment on a mapbased mobile navigation assistant (i.e. a digital navigation
assistant on a handheld device where the user is presented
with a wider map). Specifically, automatic rotation,
physical rotation and manually operated digital rotation
were compared against a baseline north-up condition to see
which method was the most effective. Effectiveness was
measured in terms of navigation performance (timings,
errors and disorientation events), perceived workload and
spatial orientation.
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April 28-May 3, 2007 • San Jose, CA, USA
Participants
The compass was mounted on the user’s shoulder rather
than on the back of the PDA because, in testing, the backof-the-PDA platform appeared to be associated with a great
deal of heading instability. Heading instability is known
result from tilt variations, including any variation of the
platform, motion, acceleration, deceleration or random
vibrations; it can also be induced by magnetic fluctuations
from electrical activity in ac or dc current carriers near the
compass [18]. In testing, it also appeared that very large
degrees of tilt could lead to inaccurate compass readings
(e.g. the map was completely misaligned). This factor also
favoured the shoulder position since test users often held
the PDA down by their side whilst walking.
Sixteen paid volunteers, 8 females and 8 males, took part in
the experiment. All were students at the University of
Nottingham, UK, and were unfamiliar with the area in
which the experiment was to take place. They were aged
between 19 and 27 (mean =21.9). All verified that they had
normal, or corrected to normal, eyesight. All owned and
used mobile phones, but had little or no experience of
handheld computers, and none had any experience of using
maps on mobile devices.
Experimental Design
The experiment used a repeated measures design. The
independent variable, rotation type, contained four levels:
automatic rotation, manual rotation (i.e. using buttons),
physical rotation and a north-up alignment condition. Route
and order effects were controlled by counterbalancing
routes and conditions. Participants experienced the routes in
the same order but experienced the conditions in one of four
different orderings. Equal numbers of participants were
randomly assigned to each ordering (4 to each ordering, 2
male and 2 female).
Routes
Four routes were designed in Nottingham, UK. Each was
approximately 800 meters in length. To successfully
navigate the routes, participants had to travel to two
waypoints followed by the route destination. Altogether,
they needed to make 8 correct turns. On the map, the route
origin was marked as “A”; the first and second waypoints
were marked as “1” and “2” respectively and the
destination was marked as “B”. Participants were only able
to see one route at a time.
Materials
A basic map application was developed in Flash MX for
use in the north-up and physical conditions. It presented the
user with a digital map of the area in which the experiment
took place. Users could pan the map by dragging a stylus
across the iPAQ’s touch-sensitive screen. They could also
adjust the scale using plus and minus controls positioned in
the bottom right-hand corner of the screen (see Figure 1
top). This basic map application was adapted for the manual
condition by adding a clockwise-anticlockwise rotation
button (see Figure 1 top). This button was the outcome of a
previous study in which alternative manual buttons were
compared [11]. For the automatic condition, the basic
application was adapted to respond to compass data that
was fed into the Flash MX application using a socket
developed in C++. The map was set to respond so that,
irrespective of the orientation of the device, map north was
aligned with real north. In both the automatic and manual
conditions, the map rotated around a point located towards
the user’s end of the screen when the device was held in an
upright orientation.
All versions of the software were presented to the user on a
personal digital assistant (PDA) (specifically, a Compaq
iPAQ model 3630 handheld computer). In the automatic
condition, the handheld computer was connected via a
serial cable to an electronic compass (Honeywell HMR
3000) positioned on the shoulder of a jacket worn by the
user during the experiment (see Figure 1 bottom). The
compass was powered by a 9 volt battery. It has been
suggested that usable heading information could be
obtained from the position of the sun [6]. An electronic
compass data was chosen because it does not depend on the
availability or visibility of the sun position (i.e. daylight and
a clear sky).
Figure 1: The map application as it appeared to the user in the
manual condition (top) and the hardware used in the
automatic condition (bottom)
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April 28-May 3, 2007 • San Jose, CA, USA
Dependent Measures
their orientation. They were then asked to rotate themselves
to see how the map re-aligned.
Performance on the navigation tasks was measured in terms
of timings, errors, disorientations, and perceived workload.
Errors were counted when the participant deviated from the
route by more than 5 meters. Disorientations were coded on
the basis of video recordings that were taken of each
participant on each route. They were defined as events
where participants stopped for more than 20 seconds, or for
between 10 and 20 seconds where there was some verbal
confirmation of disorientation (e.g. the participant said
“where am I?”). Perceived workload was measured using
the NASA Task Load Index (TLX) [5]. This is a widelyused measure of subjective workload. Participants are
required to read descriptions of six workload dimensions
(effort, mental demand, frustration, temporal demand,
performance and physical demand) and then to rate the
experimental task on each of these dimensions1.
In all conditions, following training, participants were
orientated to real north and map north. Then, they were
shown their position on the map (the starting point for the
route marked “A”) and were told that their task was to
navigate to the destination (marked “B), via the waypoints
(marked “1” and “2”). They were asked to walk as quickly
as possible and to take the shortest possible route. In the
physical and manual condition, they were instructed to
maintain a track-up strategy, whether or not they typically
adopted a track-up strategy with a paper-based map.
Similarly, in the north-alignment condition, they were
asked to maintain the PDA in a fixed orientation, with north
at the top of the map, whether or not they typically did so.
The experimenter accompanied each participant on each
route. If any errors were made, participants were directed
back on to the correct route after walking 5 metres in the
wrong direction. During each route, the experimenter video
recorded and timed the participant and pointed out one
landmark (for the subsequent spatial knowledge tests). At
the end of each route, the NASA TLX and the spatial
knowledge tests were administered and a semi-structured
interview was carried out. It took approximately 2.5 hours
for each participant to complete the experiment.
Spatial knowledge was measured using two tests. In the
first test, standing at the route destination, participants were
asked to face north and point to several locations along the
route (the route origin, the two waypoints and an additional
landmark). In the second test, participants were given a test
sheet that contained two landmarks (the route origin and
destination); their task was to place three other landmarks
(the two waypoints and an additional landmark) in relation
to these two points. Both tests have been widely used by
cognitive mapping researchers.
RESULTS
Procedure
Preferences
Participants took part in the experiment individually. At the
beginning of the experiment, it was explained that they
would be asked to navigate four routes using a different
navigation aid on each route. They were informed that some
people rotate paper maps when they change direction so
that “up” on the map is aligned with their forward direction.
All participants said they understood this concept and were
able to demonstrate their understanding by physically
rotating a paper map into a track-up alignment. They were
then given training in how to use the basic map application
i.e. the pan and zoom controls were demonstrated, and they
were given time to practice using them.
At the end of the experiment, participants were asked to
state their first, second, third and fourth preferences. The
results are presented in Figure 2. As the figure indicates,
physical rotation was the most popular, cited by six people
as their first preference and by no one as their least
preferred option. Manual rotation was least popular, cited
by only two participants as the first preference and six
participants as the least preferred. Automatic rotation
received a varied response with five people rating it as their
first preference and four people rating it as their least
preferred option.
Each participant followed the routes in the same order. The
conditions were varied to achieve counterbalancing
between routes and conditions. At the beginning of the
manual condition, participants were given training in how
to use the rotation buttons: after a demonstration, they were
asked to face north and then to align the map to north using
the buttons. At the beginning of the automatic condition, it
was explained that the map would automatically align to
Preferences
18
16
Frequencyn
14
12
4th
10
3rd
8
2nd
6
1st
4
1
2
High levels of mental workload can distract users from
other aspects of the navigation task (e.g. planning) and from
concurrent tasks or activities. Also, it is likely that users
prefer to navigate with minimum frustration and effort.
0
physical
automatic
north-up
manual
Condition
Figure 2: Preference for each condition
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April 28-May 3, 2007 • San Jose, CA, USA
Timings, Errors and Disorientations
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Figure 4 shows how many errors and disorientations
occurred within each condition. Since the distributions on
both variables showed large departures from normality,
significance testing was carried out using Friedman’s Test.
There was a significant main effect for rotation type with
respect to disorientations (χ2=7.482, d.f.=3, p=0.058). Posthoc analyses using Wilcoxon Signed Rank Test evaluated
all pairwise differences between the four conditions.
Participants were more frequently disorientated in manual
condition compared to the physical condition (z=-2.360,
p=0.018). Two other contrasts were very close to
significance: compass versus physical (z=-1.890, p=0.059)
and north-up versus physical (z=-1.897, p=0.58). Taken
together, the data suggest that people were less
disorientated in the physical condition compared with the
other three conditions. There was no evidence of a main
effect for rotation type with regard to errors (χ2=3.046,
d.f.=3, p=0.385). A repeated measures ANOVA of the
timing data found no main effect for rotation type (F=0.452,
d.f.=3, p=0.717).
Mental demand
M
an
ua
l
N
or
th
-u
p
Effort
Ph
ys
ic
al
Au
to
m
at
ic
Mean ratings
Perceived workload
Condition
Figure 3: Perceived workload for each condition
Frequency of errors and disorientations
16
14
Frequency
12
Spatial Knowledge
10
Each spatial knowledge test (the pointing task and the cued
spatial response test) provided a set of direction estimates.
The direction estimates were obtained from the cued spatial
response test by measuring the angle between the
destination and each of the locations marked on the test
sheet. In both datasets, the raw direction estimates were
converted into absolute error scores (i.e. the unsigned
difference between the estimated and actual angle) and then
averaged within each condition to give a mean absolute
error score for each participant in each condition. Repeated
measures ANOVAs failed to find main effects for the either
the pointing direction estimates (F=1.391, d.f.=3, p=0.258)
or the direction estimates derived from the cued spatial
response test (F=1.434, d.f.=3, p=0.245). In other words,
there was no evidence of better cognitive map formation in
the north-up condition.
Errors
8
Disorientations
6
4
2
M
an
ua
l
N
or
th
-u
p
Au
to
m
at
ic
P
hy
si
ca
l
0
Condition
Figure 4: Frequency of errors and disorientations occurring
within each condition
Workload
Repeated measures ANOVAs of the data on all six subscales of the NASA TLX revealed main effects of mental
demand (F=2.768, d.f.=3, P=0.053, partial eta-squared=
0.156) and Effort (F=2.223, d.f.=3, P=0.098, partial etasquared= 0.129) at the 0.1 significance level. Figure 3
presents the mean scores on the mental demand and effort
sub-scales in each condition. Tukey’s test assessed all
pairwise differences between the means on the mental
demand and effort sub-scales. On mental demand, the
physical rotation versus north-up contrast was significant
(q=-4.05, d.f.=15, P<0.1) while the physical rotation versus
manual rotation contrast approached significance (q=--3.26,
d.f.=15, P<0.1). Two contrasts were found to be significant
on the effort sub-scale: physical versus north-up (q= -3.95,
d.f.=15, P<0.1) and physical versus manual (q= -4.21,
d.f.=15, P<0.1). In summary, participants perceived the
north-up and manual conditions as more mentally
demanding and requiring more effort compared with the
physical rotation condition.
QUALITATIVE RESULTS
Qualitative data gathered in the experiment included
participant comments on route, observations and responses
to the semi-structured interviews carried out at the end of
each route. Table 1 overleaf presents a summary of the key
themes that emerged from an analysis of the data.
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CHI 2007 Proceedings • Mobile Interaction Techniques II
CONDITION
PHYSICAL
AUTOMATIC
April 28-May 3, 2007 • San Jose, CA, USA
The main problem associated with physical rotation was a
concern that the handheld computer might be accidentally
dropped during rotation. One participant said he was
“scared of dropping the PDA”. When he first saw it, he
thought “yeah I could turn that around in my hands” but
then he “considered the idea of dropping it ‘oh dear’”.
Similarly, another said “it’s not something you really want
to drop”. One participant mentioned the possibility of the
stylus dropping out during rotation.
THEME
Easier than manual
Rotating hand rather than device
Dropping the PDA
Reduced workload
Changes when you're not looking
Difficult to read
Sometimes faced the wrong way
Automatic Rotation
Landmarks disappear off-screen
Better with practice
MANUAL
A number of participants indicated that automatic rotation
reduced their workload, in particular their mental workload.
One said that automatic rotation “requires less thinking on
my part” and that he didn’t need to worry which way he
was going to turn next because the map informed him
which way he was facing. Another suggested that, with
automatic rotation, “so long as you know where you are, it
tells you were to go…you can just follow the map”.
Workload & distraction
Landmarks disappear off-screen
Wrong button to begin with
Being in control of rotation
Pans instead of rotates
NORTH-UP
Other participants seemed to find the automatic interface
confusing. Their chief complaint was that the map rotated
when they weren’t looking. One person said it was
confusing because “it keeps changing so there’s nothing
fixed to come back to”. According to another, it was “a
little bit disorienting” because “when you glance up to see
where you are and you look back down, it’s totally changed
position”. Another said that he sometimes had to
compensate for the fact that “the roads were looking a bit
strange, already turned by the time I looked at it”. In other
words, following rotation, participants seemed to have
trouble recognizing the map in its new orientation.
Better with practice
High mental workload
Mental rotation & other strategies
Table 1: Key themes to emerge from the analysis of the
qualitative data
Physical Rotation
Many participants said that they found physical rotation
easier than manual. One said that it was “much easier to
physically move the thing rather than having to use the
buttons”. According to one participant, with manual
rotation, if you got it wrong, it was not easy to return the
map back to its previous orientation. By contrast, with
physical rotation, it was easy to turn the map back and reorientate it to where it was before.
TC: So at one point I can be walking down here and I’ll
see the B here and I’ll know I’ll have to turn and then
I’ll be turning and the B will be somewhere else and I’ll
have to, in my head I’ll have to put everything into the
same place, kind of move it around like this and say it’s
still the same B, it’s just that it’s changed on the thing.
Many participants did not hold the device in “side-on”
orientation. When heading east or west, they rotated their
hand rather than the device (see Figure 5). Several indicated
that the “side-on” orientation was not comfortable. Also,
there were concerns that the device might be dropped if
held in a side-on orientation.
a)
A few participants commented that the map sometimes
moved too much while they were looking at it. According
to one participant “it wasn’t very good because it flickers
around a fair bit”. Another suggested that it was “hard to
look at constantly moving”. He said it would be easier to
read if it were still and he could just look at it and see where
he was without the map moving. Another participant
suggested that the map should stay stable while he walked
and only turn when he changed direction to walk down
another street.
On several occasions, participants found that the map faced
the wrong way. In one case, this led to reduced confidence
in the map: following an incident where the map faced
entirely the wrong way, one participant said that he lost
confidence that he was going in the right direction.
b)
Figure 5: When heading east or west, many people rotated the
PDA by twisting their hands (a) rather than rotating the whole
PDA (b)
Several participants noted that landmarks, including key
landmarks such as the route origin and destination, could
sometimes disappear off-screen when the map rotated.
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When this happened, participants were forced to readjust
the map to bring the landmarks back on screen. Note that
the same problem occurred with manual rotation.
because she found it “hard to get my head around the whole
like where I am in it”. Many said that the track-up
conditions were easier. For instance, one participant said
that in the track-up conditions, he didn’t need to think. He
just made sure the map was aligned and then followed it
“step by step, road after road”. The task was just to go
straight “to the north part of the screen…the road I was
looking at was always straight ahead”. Another participant
made a similar remark: “turning the map is easiest, you just
follow the road”.
Manual Rotation
Participant comments with regard to manual rotation were
consistent with the relatively high mean mental workload
and effort scores on the NASA TLX. For example, one
participant said that she experienced quite a lot of
frustration rotating the map using the manual buttons. She
attributed a period where she became lost to the fact that
she was thinking more about rotating the map than seeing
where she was going. Another participant said that “with
the extra task of moving [the map] around…it’s easy to lose
track of where you are”. She also said that the manual
rotation task stopped her from monitoring her position on
the map using her finger.
Some participants discussed the strategies they used to
compensate for misalignment. For the most part, they
referred to mental rotation. For example, one mentioned
how, when traveling south, he rotated an image of the map
in his mind. Other participants used a strategy of reversal of
interpretation. For instance, one said that when she came to
“cross sections and stuff and you’re like hang on a sec
that’s right on the map but it’s left in real life”. One
participant mentioned that she sometimes turned herself to
align the map.
One participant indicated that, to begin with, she chose the
wrong button. During a right turn, instead of using the lefthand rotation button to rotate the map anti-clockwise, she
pressed the other button (i.e. the clockwise button
positioned on the right). She had apparently associated the
button position with the direction of the turn i.e. she was
turning right so she pressed the right-hand button. However,
she quickly learned to press the correct button and did not
view it as a major problem.
DISCUSSION
The study outlined in this paper contrasted three ways of
maintaining track-up alignment on a mobile device: manual
rotation, physical rotation and automatic rotation. All three
were compared against a baseline north-up condition. Only
physical rotation was found to be significantly more usable
than north-up alignment. Specifically, people were able to
navigate with lower mental workload, effort and fewer
disorientation events when they physically rotated the PDA
in a track-up alignment compared with the baseline northup alignment condition. In addition, there were strong
indications of trends towards better performance with
physical rotation on the other dependent variables (e.g.
timings and errors and the other dimensions of workload).
Plus, more people cited physical condition as their first
preference than any other condition and no one cited it as
their least preferred option.
Again, compared to automatic, some participants liked the
fact that, with manual rotation, they were in control of the
rotation. One said that he preferred it to automatic because
he could turn it when he wanted to. He said that he
preferred not to turn the map on every street.
Several participants said that they accidentally panned the
map when they had meant to rotate i.e. they missed the
rotation control and panned the map instead. They found
this frustrating because they were forced to waste time
readjusting the map so the route was visible again. Possibly,
the control area surrounding the button was not large
enough, but it also points to the fact that buttons on mobile
devices are difficult to operate when on the move.
As noted earlier, there have been two other investigations
into map alignment on mobile devices. One study compared
manual map rotation with automatic map rotation via a
head-mounted display [14]. This study found no difference
between the two forms of rotation. The other study was
carried out by Hermann et al using handheld computers [6].
Here, automatic rotation was compared with physical
rotation and a north-up alignment condition. Hermann et al
study found that participants navigated more quickly and
with fewer errors in the automatic condition followed by
the physical rotation condition.
Several participants said that they found that manual
rotation became easier with practice. One said that while, at
the beginning of the route, he had to stop to rotate the map
by the end of the route he was able to turn the map as he
was turning a corner. Most participants, however, did not
learn to rotate the map while moving; most were observed
stopping to operate the buttons even near to the end of the
route. Several participants had also mentioned that
automatic rotation became easier with practice.
The apparent inconsistency between the results in this study
and the Hermann et al study can be explained by the
different type of information presented in the two studies.
In the Hermann et al study, participants were presented
navigation information using a turn-by-turn format. At any
one time, they were presented with the next turn along the
route. Specifically, they were presented with a position
North-up
In general, participants indicated that they found the northup condition difficult. For example, one participant said that
with north-up alignment, he was “looking more at the PDA
than in the other conditions, using my brain for more info”.
Another said “it’s quite hard when you can’t turn it”
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symbol, route highlighting showing a single turn and some
surrounding information (see Figure 6 left). In the current
research, participants viewed a more complex map that
wasn’t focused on a single turn (see Figure 6 right).
the route origin and destination, could sometimes disappear
off-screen. This problem was partly due to the fact that
users generally positioned the map so that the end-points of
the route were near to the edge of the screen. Presumably,
they did this to maximize the scale of the map.
While performance was highest in the physical condition,
physical rotation was associated with some difficulties. In
particular, participants were concerned that they might drop
the PDA and some participants experienced difficulties
holding the PDA at certain angles. Also, it’s likely that
some users may have experienced difficulties reading
upside road labels. This is likely to be a much bigger
problem for applications that present the user with larger
amounts of text (e.g. location-based tourist guides): even
users who are able to read upside street names may find it
more difficult to read sentences that are upside down. Plus,
users may have difficulty operating controls that are not in a
fixed orientation.
Figure 6: Format used in the Hermann et al (2003) study
(left) and a map-based format (right)
DESIGN
This section discusses some of the possible design
implications of the study.
It’s likely that different cognitive processes are used to
interpret the information in each case. With the format used
in the Hermann et al study, users are required to interpret an
unfamiliar turn. Their task is to determine whether the turn
is left or right, and perhaps also the angle of the turn, and to
relate this information to environmental information ahead.
In the study reported in this paper, participants would have
been presented with a rotated version of a map they had
already acquired some familiarity with. In this case, the task
may have been to recognize the map in its new orientation.
This was reflected by participant comments. Many
indicated that they had difficulty recognizing the map in its
new orientation; in particular, they had trouble finding key
locations such as their current position, the waypoints and
stages of the route they had already planned.
Improving physical rotation
A better grip and a more robust and robust-looking PDA
design could increase user confidence in holding and
rotating the device and reduce fear that the PDA might be
dropped.
Physical difficulties holding the mobile device in certain
orientations could be overcome by changing the shape of
the device. For example, a round shaped device could be
held equally well at any angle (see Figure 7a). However,
it’s possible that certain affordances would be lost with the
removal of the rectangular frame. Possibly, the rectangular
frame provides visual and tactile feedback that is helpful to
users in deciding which way to rotate the device and/or
when to stop rotating. It may also help users remember
which way they were holding the device after letting the
device drop to their side.
It’s also possible that physical rotation is easier with a mapbased format. With turn-by-turn presentations, participants
must align a novel presentation each time. When presented
with a wider map, it’s likely that users will develop
familiarity with the map, which may help them to
physically align it.
One possible solution to the problem of upside text and
controls would be to have the text and controls rotate along
with the device. Compass data could be used to determine
how the PDA is orientated in relation to the user; the
software could use this data to present text and controls in
an upright orientation from the user’s perspective. Since
people generally hold paper maps and handheld computers
with one of the sides towards themselves, the preferred
option might be to present the text and control areas in one
of four orientations. This would also ensure that there was a
consistent area for the presentation of the text and controls
(i.e. the length of the shorter screen side). Figure 7(b)
illustrates how this design might look in a north-up and
west-up orientation.
Manual rotation performed poorly in comparison to
physical rotation. Participants experienced high levels of
workload. This was indicated by their responses to the
NASA TLX, their comments and by their behaviour. One
explanation is that physical rotation provides much stronger
feedback. While manual rotation provides visual feedback
in the form of a rotating map, physical rotation provides a
rotating map and a rotating frame. Physical rotation also
provides strong tactile and kinesthetic feedback i.e. how the
device feels at different orientations and the motion of the
device as it rotates.
One issue that appeared to affect both manual and
automatic rotation was the fact that key landmarks, such as
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Note that some in-vehicle navigation systems deliver
“intelligent” rotation using GPS. However, GPS alone
might not be sufficient for pedestrian navigation systems
for several reasons. First, pedestrians travel at much slower
speeds than most vehicles. If the system relied on GPS, the
map wouldn’t turn until some time after the user had
turned, given that GPS is generally only accurate to within
10 to 20 meters. Also, pedestrians are more likely to be
affected by “urban canyons” (areas where satellite signals
are blocked by nearby buildings). Secondly, unlike
vehicles, pedestrians often stop, turn on the spot, and walk
in the opposite direction. Only compass data would enable
the system to react quickly to such turns. Thirdly, in
contrast to cars, pedestrians often travel through open
spaces such as parks or squares where there’s no obvious
road network.
a)
Improving manual rotation
It’s possible that users would find a “left turn/right turn”
(LTRT) rotation button more intuitive than the CW/ACW
button. With a LTRT button, the user would press an arrow
pointing right when turning right, and an arrow pointing left
when turning left. However, it may be that some users
would interpret it as a CW/ACW button (i.e. when they
press the RT button, they expect the map to rotate in a
clockwise direction). Further testing could establish
whether one design is considered to more intuitive by the
majority of users. Note, however, that misinterpretation of
the CW/ACW button was not a major issue. Only one
participant out of 16 mentioned it and she said it was only a
problem at the beginning of the route.
b)
Figure 7: (a) Round device; (b) Rotating text and buttons
Improving automatic rotation
A combination of GPS, map matching techniques, and
compass data could be used to provide a smarter form of
automatic rotation. As noted earlier, a number of
participants in the final study indicated that they would
have preferred a more stable map. Some indicated that the
slight side-to-side movement made the map difficult to
read. Others said that they found rotation in certain
situations unexpected and confusing (e.g. when they looked
around whilst stationary or when they crossed roads).
Manual automatic
With a manual automatic interface, the user would press a
single button and the map would automatically align using
compass data. This may address many of the problems
associated with automatic rotation. This would produce a
stable map when the user was walking along, which would
be easier to read. In addition, it would solve the problem of
unexpected or unwanted rotation when the user was
standing still. Here, manual automatic may have an
advantage over “smart automatic rotation” in that the user
could, for example, choose to align the map while looking
east on a north-south road. It would also encourage the user
to look at the map when the map was rotating, thereby
reducing the likelihood of map recognition problems (i.e.
difficulty understanding the new orientation of the map). A
manual automatic interface would also address some of the
problems associated with manual rotation. There would be
no choice between buttons and so no danger of choosing the
wrong button. Also, it’s likely that the workload associated
with manual automatic rotation would be greatly decreased
relative to manual rotation. The user would not have to
concentrate as much on alignment (i.e. waiting for the map
to align before depressing the button). Rather, the user
would simply need to press a button once and watch briefly
as the map aligned automatically.
With knowledge of the road network and GPS, as well as
compass data, the map could be set to rotate in relation to
the street rather than the person. For example, if the user
was heading south on a north/south street, the system could
orientate the map to be south-up. The general choice of
orientation could be determined by knowledge of the
location of the user on the road network. The heading on
the street could be determined by the compass data (e.g. if
the heading fell between 90 degrees to 270 degrees, the
map would orientate to south-up).
Again, at corners, re-orientations could be determined using
a mixture of location data, compass data and knowledge of
the road network. GPS data tells the system that the user is
within the vicinity of a certain turn. With knowledge of the
road network, and compass data, the system could orientate
to one of the street headings (e.g. at a T junction, there
would be three possible orientations).
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edited by P. Hancock, & N. Meshkati (Amsterdam:
North Holland), (1988), 139-183.
With the manual automatic interface, users may still find
that landmarks disappear off-screen as a result of rotation.
One way to solve this problem would be to present users
with a round map display. If the map rotated around a point
at the centre of the display, all information currently within
view would remain on-screen. The main drawback of this
approach would be the sub-optimal use of screen space i.e.
less map would be displayed.
CONCLUSION
The results of this study provide strong evidence that
physical rotation is the most effective form of track-up
alignment for map-based navigation assistants on handheld
mobile devices. While automatic rotation may be the more
effective with turn-by-turn based instructions, physical
rotation is more suitable for navigation assistants that
present the user with a wider map. The key reason is that
users find it difficult to recognize a map that rotates
automatically when they are not looking at the map. It is
suggested that designers of map-based interfaces support
physical rotation (e.g. by providing good grip and a robustlooking handheld computer). Further research is needed to
establish whether alternative designs such as “manual
automatic rotation” are viable alternatives to physical
rotation.
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