Landmarks: A Thought Experiment - Landmarks: GIScience for Intelligent Services - page 35

For example, if the coin would have been found along an edge, not at a node, any of
the following would be a natural reference: “Near corner West fourth St and Prime
Avenue”, or “In West fourth St, 30 steps from Prime Avenue”, the latter implying
an intersection of the two streets.

2.1.4 Filling with Further Landmarks

Now let us imagine the cells enclosed by network edges and nodes are filled with
white blocks, larger than the human body. These blocks limit the sight of walkers.
Since they are plain white without further texture or structure they are nearly
indistinguishable for the human senses. There is no particular bodily experience
attached to the encounter of any individual block except the shape of the cell they
occupy.
These blocks get more importance in our experiment if we give them individual
faces or meanings. Individual blocks can get attached a special shape, or a special
color. A block can be labelled “supermarket”, and another one “café”. These blocks
stand out from the other ones that were left unchanged plain white. They provide
a special experience for passersby. Walkers will memorize these experiences, and
attach them to the locations where they make these experiences. As long as these
labelled objects are globally unique and only few they can have global landmark
characteristics. “In the direction of the supermarket” provides global orientation
if everybody knows the supermarket. They can also take the function of local
landmarks. People can refer to it when describing local events (“in front of the
supermarket”, “three blocks from the supermarket”), either trusting that the recipient
has made the encounter with the supermarket before already, or will easily identify
it when passing by. “At the supermarket” is an even more efficient description than
“at the third intersection” because it does require only one object recognition task,
and no counting.
However, landmarks do not have to be globally unique. There might be a second
supermarket in this environment, perhaps even of the same brand, as it happens out
there in any real city. The two supermarkets are still differentiable from the rest of
the environment, but an instruction such as “At the supermarket” must be considered
ambiguous now. There are three common cognitive mechanisms that are used for
disambiguation of local landmarks in a communication context:

1. Nearness : “At the supermarket” is disambiguated by choosing the nearest indi-
vidual as a default. Behind this cognitive heuristics is also embodied experience
since the cost of interaction with the environment is inversely proportional to the
cost of travel: the nearest supermarket is the easiest one to reach. The argument
is additionally supported by the first law of geography as stated by Tobler:
“Everything is related to everything else, but near things are more related than
distant things” ([ 20 ] , p. 236).