![](bg3.png)
of GraphHopper is its customizability concerning the
creation of different profiles for instance to represent
different vehicles as different profiles in GraphHop-
per (Karich, 2019b)(Karich, 2019a). For example, a
profile can be created that corresponds to the pedes-
trian profile but additionally avoids all stairways that
are tagged as such in OSM.
2.3 Open Route Service
Open Route service, developed and provided by
Heidelberg Institute for Geoinformation Technology
(HeiGIT), offers routing services by using user-
generated, collaboratively collected free geographic
data from OSM (Heidelberg Institute for Geoinfor-
mation Technology, 2019). The platform provides
the function of routing, based on profiles, including a
wheelchair profile, also through its newly developed
mobile application. This wheelchair profile is cus-
tomizable by its users, directly on the platform. For
instance, it can be customized to avoid cobblestone or
flattered cobblestone as ground surface during rout-
ing. Parameters such as the width or the incline of
a path can be customized as well. Furthermore, it is
possible to examine the percentage of a path consist-
ing of a particular type of surface. However it does
currently not support adding new barriers to the sys-
tem which is a major requirement four the work, see
section 3, and the profile settings are not fully cus-
tomizable (Google, 2021b).
2.4 Wheelmap and Accessibility.cloud
Wheelmap is a charity-based navigational service
available to the public for reading requests. The map
helps to find wheelchair-accessible places similar to
points of interest on Google Maps. Lots of places
such as grocery stores, shops, hotels, bars, restau-
rants, pharmacies, public parking garages, and many
more are listed in four different categories depend-
ing on whether the place is entirely, partially, or not
at all accessible or if the accessibility is unknown
(Krauthausen, 2010). While Wheelmap itself serves
as the frontend, the API named accessibility.cloud is
both backend and data source of it. The accessibility
information from this API is provided to the public to
be used in other applications as well. For scientific
purposes, its usage is free of charge. Both projects,
Wheelmap and accessibility.cloud are initiatives of
the non-profit organization SOZIALHELDEN e.V.
(accessibility.cloud, 2021).
Even though it is shown whether the place itself is
wheelchair accessible or not, the map does not show
if a wheelchair can handle the way to the place. Al-
though it hence cannot be used for routing directly, it
can help to find barrier-free points of interest such as
restrooms or stores that the user can navigate to.
2.5 Google Maps
The most popular navigation service, at least in the
western world, is Google Maps. Today, it is an in-
dispensable companion for almost anyone in daily
life (Poleshova, 2020). Although its usage is conve-
nient for vehicle drivers, cyclists, or just pedestrians
since suitable profile exists for each of those differ-
ent ways of transport, no such profile is available for
wheelchair users. This is a big limitation, considering
that stairways, uneven surfaces, and other insupera-
ble barriers may require users to find alternative ways
around them on their own. Even though Google intro-
duced a feature to find wheelchair accessible routes,
the service is currently only available in six cities, and
none of them is in Germany (Akasaka, 2020). Bring-
ing this together with the fact, that their API usage is
not free of charge (Google, 2021a), it is currently nei-
ther utilizable as a source for map material nor as a
navigational system for physically limited people it-
self.
3 METHODOLOGY
In this section, the feature requirements, the strategy
for the development process, and its resulting design
and architecture is explained.
3.1 Requirement Analysis
Since the navigation system is being developed in col-
laboration with this LAPIC association, mentioned in
section 1, the desired features were evaluated primar-
ily through surveys with mobility-impaired individu-
als from the association. Based on the result of the
surveys the following core features were elaborated:
• Routing under consideration of barriers such as
stairways, uneven surfaces, bottlenecks, and in-
clines.
• Creation of individual profiles to take into account
the physical limitations of the user in the routing
process accordingly.
• Adding new barriers or modification of existing
barriers to the system by its users. This includes
as well temporarily existing barriers such as fallen
trees or road constructions.
Since it turned out, as described in section 2.1, that
the database of OSM already contains a lot of relevant
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