Geography Reference
In-Depth Information
Further, latency and positional errors of the GPS produced some directions too late
or at the wrong locations, which harmed navigation ease and success.
The correct timing of verbal instructions for GPS-based navigation systems
was addressed by Rehrl et al. [ 55 ] . They tested instructions using either metric
information or landmark references to indicate where to turn. Participants navigated
test routes in the city of Salzburg wearing headphones that canceled most of
the street noise. An instructor shadowing the participants triggered instructions at
pre-defined locations to avoid any timing issues that may result from poor GPS
positioning. Similar to the SpaceBook project, these instructions were voice-only,
no graphical route information was provided to the participants.
Overall, the study showed that the correct timing of unambiguous instructions
is most crucial for successful wayfinding. Landmark references help removing
ambiguity. While the type of instructions had no effect on walking time, participants
made notably fewer navigation errors when using the landmark-based instructions
compared to those receiving metric references. Basically, participants did not use
metric information at all, but simply waited for the next instruction to come, whereas
landmarks helped them to identify correct turns.
The system of Hile et al. [ 34 ] (see Sect. 6.2.2 ) combines photographic views
along a route with verbal instructions. In their evaluation, participants could switch
between a photo view and a map view. Most used both in their navigation, with
the photo view mostly applied in critical, ambiguous situations. The participants
perceived a range of the presented photographs as confusing, because in the real
world trees blocked the view to the landmark depicted on the photo and referenced
in the verbal instructions, and because photos did not coincide with the participants'
perspective. In the latter case, participants had to mentally transform the perspective
seen on the photograph to the perspective they had while moving, which is a
cognitively demanding task. This clearly indicates that while graphical landmark
references, and especially photographs, can be a powerful support for human users
of a service, a careful selection of these photographs is crucial. Hile et al. addressed
some of the issues identified by the study participants in some follow-up work [ 35 ] .
Beeharee and Steed [ 4 ] got similar results from their user evaluation. Participants
were clearly faster with photo-augmented instructions compared to only map views
because they could use the photographs to disambiguate situations and to confirm
that they were on the right track. But photos not taken directly from the participants'
perspective, or in a different season, or different lighting conditions may confuse
(some) users as again there is a perceptual mismatch that requires cognitive effort
to resolve.
Wither et al. [ 68 ] compared their panorama view based navigation service (with
and without enlarged business signs) to a 'traditional' map based navigation mode
(again with or without enlarged business signs). They found no difference in
navigation performance between the different modes. However, other than expected
participants spent more time looking at the panorama view than on the map. Initially,
Wither et al. hypothesized that panoramas were easier to match to the real world,
since they essentially reproduce the perspective in the real world directly. But it
seems that both increased visual complexity of panorama images and people's prior
 
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