Computational Aspects: How Landmarks Can Be Observed, Stored, and Analysed - Landmarks: GIScience for Intelligent Services - page 148

Obviously, all the approaches presented in this section can only find what is in
the sources. Their results depend on the available data, i..e, on what people upload to
the Internet. Thus, these approaches are very good at picking up the most prominent
locations in a country or city, where there will be many uploads (often from tourists),
but will fail to pick up local landmarks in some residential neighborhoods because
only very few, if any, data is published about them. This issue will be further
discussed at the end of this chapter in Sect. 5.5 .

5.3 Landmark Integration

When a set of landmark candidates exists, these can be used in a range of services,
some of which we will discuss in the next chapter. Most of the times, this will
require selecting one—or a very few—landmarks from the set of all candidates.
This is necessary because not all landmark candidates will be relevant for a given
situation or task. And often it will be the case that the landmark that gets selected
is not the most outstanding of the whole set, according to the salience measure
applied. Rather, it will be the most relevant landmark. Accordingly, this section
covers several approaches to determining relevance of a landmark candidate for
specific tasks and situations, predominantly in navigation scenarios.
Klippel and Winter [ 26 ] , for example, extended the salience model by Raubal
and Winter [ 35 ] in order to select a landmark at an intersection that is most suitable
to initiate a turning action (e.g., 'turn left' or 'veer right'). Figure 5.7 illustrates
possible locations of landmarks with respect to turning at an intersection. Not all
landmarks are equally suitable for identifying the required turn.
The location of a landmark relative to a turn at an intersection is an aspect
of structural salience. The extended model uses advance visibility, as it has
been discussed in the previous section, but additionally takes into account the

Fig. 5.7 Possible locations of landmarks with respect to turning actions; modified from [ 26 ]