Open Historical Data Map (OHDM) - work in
HTW (University of Applied Sciences)
Digitizing old maps is an ongoing work in numerous
libraries worldwide. A scanning process creates a so-called
raster graphic. Those pictures are made up by a raster in which
each cell contains a number which describes the color.
Raster graphics are perfect for humans. Vector graphics are
the preferred input for computer programs, though. Vector data
describe geometries instead of colors and their position. A
vector point e.g. is described by longitude and latitude. A
street can be described by a number of such points. Vector
geometries are required for any computer based calculation
on maps, e.g. route ﬁnding and calculating length of streets.
Producing accurate vector geometries is a resource intensive
process, though. Public land surveying ofﬁces are and were
responsible for those tasks in most countries.
Open Street Map (OSM) is an example how a huge crowd
of enthusiastic volunteers can create an accurate and up-to-
date global map based on vector geometries. We are going
to offer a similar system with some more services but with
historical data. That is Open Historical Data Map (OHDM).
The OSM schema is mainly based on points (node in OSM
terminology). Ways are made up by nodes an relations help to
describe that e.g. an university is logged in several buildings
which are not necessarily physically connected.
OHDM has a more complex data model. OHDM distin-
guishes between geographic objects and their geometries, see
Geographic object are e.g. buildings, streets, boundaries of
countries. They have a life-cycle: They are created, changed
and cease to exist sometimes. Objects and geometries are
related but not the same. The obelisk on the Place de la
Concord in Paris was moved there in 1835. It was created
centuries ago in Egypt, though. That object (obelisk) changed
its position (geometry) but is still same object (obelisk).
On the other hand, geographic object might vanish but
their geometries are re-used. HTW Berlin e.g. is logged into
buildings in which a factory produced cables in former times.
Geometries, geographic objects but also their relation changes.
Those changes represent history.
OHDM will perform an annual import of OSM data. OSM
deﬁnes geographic objects only implicitly. Information of ge-
ographic objects must be extracted during the import process.
Imported data can be changed afterwards which makes
OHDM also a changeable OSM archive.
Older data must be found in other sources. Volunteers are
the only source in OSM. We also use that source and offer
editors. There are yet two prototypes: a web editor (based
on OpenLayers) and another on Android. An iOS edition is
Geometries of streets or buildings tend to be stable over
centuries. Their names or usages change more frequently,
though. Editors can be used e.g. to add an old name to an still
existing street or to explain former usage of a still existing
building. Editor can also be used to chart geometries which
do no longer exist on Earth surface [Leh16].
OHDM stores vector data in a PostGIS database. We use
GeoServer1) to offer a maps with the standardized WMS
interface [Fra15], [Thi15].
Basis of route ﬁnding algorithms are vector geometries of
streets and an average speed. More sophisticated algorithms
use current information about roadworks and trafﬁc jams to
ﬁnd the best road.
That not sufﬁcient when fro historical route ﬁnders. Firstly,
people in the past hardly used just a single vehicle for longer
trips. For some areas, carriages might have been an appropriate
way, ships or horses might be preferred in other regions.
Moreover, a noble could travel easier, faster and more safe
than a peasant e.g. in the Middle Ages. Military campaigns,
epidemics and other regional disasters made it even impossible
to pass an area. Thus, average speed strongly depended on
social status and available money. Crossing borders or coun-
tries was and is regulated by (sometimes cruel) laws which
depend(ed) on nationality, race, religion, gender and even age.
(Only retired East Germans were allowed to travel to western
countries before 1989. Woman are still not allowed to drive a
car in Saudi-Arabia).
OHDM has to store not only maps but also information
about disasters, wind directions, currents in the sea etc. pp.
That issue is at least described in detail, see [Bos16].
We also extract vector geometries from digitized old maps
in co-operation with Berlin State Library [HWSS16].
We are going to offer (1) tools to add historical spatial data,
(2) historical maps and a (3) a historical route ﬁnder (ﬁg 2).
OHDM is still in a prototype stage but concepts are clear
and the ﬁrst implementation steps are made.
Figure 1: Data model - core concept
Figure 2: OHDM Components
[Leh16] Lehmann, Marc: Entwicklung eines Web-Editors zum Bearbeiten
von Kartenmaterial mit einer Zeitachse OHDM
HTW Berlin, Bachelor-Thesis, 2016
[Bos16] Bosnar, Boris: Routensuche anhand mit historischen Karten
HTW Berlin, Bachelor-Thesis, 2016
[Fra15] Franken, Adrian: Erzeugung von Kartenmaterial mit Style Layer
Descriptoren auf der Basis von Geoserver in OHDM
HTW Berlin, Bachelor-Thesis, 2015
[Thi15] Thiele, Stephan: Eine Tileservers fuer OHDM basierend auf
HTW Berlin, Master-Thesis, 2015
[HWSS16] Hirsch, Thomas; Westphal, Florian; Saeger, Kai; Schwotzer,
Thomas: Vectorisation of historical maps
Exploring Old Maps (workshop), Luxembourg, June, 8. 2016