The Annotation Process in OpenStreetMap

In this article we describe the analysis of 25,000 objects from the OpenStreetMap (OSM) databases of Ireland, United Kingdom, Germany, and Austria. The objects are selected as exhibiting the characteristics of heavily edited objects. We consider heavily edited objects as having 15 or more versions over the object's lifetime. Our results indicate that there are some serious issues arising from the way contributors tag or annotate objects in OSM. Values assigned to the name and highway attributes are often subject to frequent and unexpected change. However, this tag flip-flopping is not found to be strongly correlated with increasing numbers of contributors. We also show problems with usage of the OSM ontology/controlled vocabularly. The majority of errors occurring were caused by contributors choosing values from the ontology by hand and spelling these values incorrectly. These issues could have a potentially detrimental effect on the quality of OSM data while at the same time damaging the perception of OSM in the GIS community. The current state of tagging and annotation in OSM is not perfect. We feel that the problems identified are a combination of the flexibility of the tagging process in OSM and the lack of a strict mechanism for checking adherence to the OSM ontology for specific core attributes. More studies related to comparing the names of features in OSM to recognized ground-truth datasets are required.