Landmarks: A Thought Experiment - Landmarks: GIScience for Intelligent Services - page 29

This expression could refer to the direction in front of herself (“put yourself in my
position; straight in front of me”), or could have referred to the direction in front
of the friend (“from your position walk straight”). For the prior interpretation, the
recipient must transform the instruction by a mental rotation from the orientation
of the speaker to their own orientation. For the latter interpretation, the speaker
must do the mental rotation before speaking. Both is practical only when speaker
and recipient are meeting face-to-face. If they are communicating over a distance
(e.g., telephone) or asynchronously (e.g., email) the communication of body-pose
related directions requires links to external cues. Since they do not exist in this
environment such a communication is simply impossible [ 10 ] . Pointing, however,
conveys the intended interpretation because it happens within the shared space [ 7 ] .
What applies to the communication of direction—the ambiguity of the reference
system, and the need for a mental transformation between reference systems either
by the speaker or the recipient—applies also to the communication of distance.
If the distance from the speaker is “about 20 steps” this information may need to be
updated by the recipient according to their different positions and step sizes, and if
the speaker actually means “about 20 steps in front of you” this interpretation needs
to be conveyed as well. These mental transformations—rotations and translations—
require spatial skills people have only to varying degrees [ 1 , 19 ] .
Stripped of any external cues within the environment, the walker will find it hard
to describe accurately the location where she found the coin. The more time passes,
or the more other walks she will have made since then, the less will she be able to
reenact the locomotion experience. Constant updating of multiple vectors (home and
all discoveries made over time) will become an overload, and the walker will give
up maintaining those vectors felt no longer to be essential (last the homing vector).
She may not necessarily forget the event itself, but she may forfeit her ability to
describe its location. For a while though, the event provided a second landmark for
thewalker.Intherealworldwehavesimilar experiences. “Let's meet at the café
where we have met first” works in communication because this café has attached
emotional value, is remembered for the meeting and for its location, and thus the
location is describable and can be found again.

2.1.3 Adding Structure

From here on our thought experiment splits for a while into three parallel streams.
One continues with constructing a memorable space (Sect. 2.1.3.1 ) , another intro-
duces a global frame of reference (Sect. 2.1.3.2 ) , and a third one defines an arbitrary
frame of reference (Sect. 2.1.3.3 ) . Each of them ends up with a network structuring
the environment, although motivated by different principles. The lines will be
reunited in Sect. 2.1.3.4 .