The description of the de facto meaning of tags TagDoc aims to provide is based on studying the data with those tags in the OpenStreetMap database. Part of this assessment is based on quantitative analysis of the data and some numbers obtained from this analysis are routinely included in the tag documentation. Here you can find a documentation of these values.
Data volume information
Data volume information in TagDoc is separated by geometry type - that is:
- Points - that is tagged nodes in the OpenStreetMap data model connecting the tags with a single 2D coordinate pair or location
- Lines or Linestrings - that is tagged linear ways in the OpenStreetMap data model
- Polygons - that is closed ways representing simple polygons in the OpenStreetMap data model - or Multipolygon relations
The distinction if a closed way (first and last node identical) represents a linestring or a polygon is based on the presence of an area=* tag, or - in the absence of such - implicit defaults based on the tags of the feature. These defaults are subject to changing conventions - which are documented on TagDoc as well.
The following numbers are provided by default:
- Feature count - the number of features in the OSM database at the time of analysis. This differs from Taginfo values (see below) because these apply to the above mentioned geometry types rather than OSM feature types (nodes, ways, relations).
- Number of nodes - the total number of nodes these features contain/reference, representing the raw amount of geometric data in those.
- Average number of nodes per feature - the ratio of the previous two values (minus duplicates in case of closed ways) - or in other words: The average number of nodes per line or polygon.
- Average segment length - the average distance between subsequent nodes of lines/polygons. This is averaged on a per feature basis, meaning that first the average segment length is calculated for every feature and then those are averaged over all features. This number differs somewhat from the overall segment length average when it was calculated flatly over all segments independent of what feature they belong to.
- Total size (in km/km²) - the total length of all lines with this tag combined (in km) and the total surface area of all polygons with this tag (in km²).
This section provides data on the use of the tag by mappers based on analyzing the OSM data history. It provides data on
- The active use of a tag (🞼), that is the creation of features carrying the tag or the addition of the tag to a feature.
- The removal of a tag (྾), that is the deletion of features carrying the tag or the removal of the tag from a feature.
- The editing of a feature (🖉) with the tag already present.
For these classes of edits the mapping activity section typically provides values on:
- The number of mappers that have performed this kind of change during the whole history of OpenStreetMap.
- The number of mappers that have performed this kind of change more recently.
- The number of edits of this class made during the whole history of OpenStreetMap.
- The number of edits of this class made more recently.
Taginfo numbers and trends
These numbers are obtained from taginfo at the time the analysis is made. They are shown separately by OSM feature types (nodes, ways, relations).
- Counts - these are the feature counts of features with the tag in question
- 30 days trend - this shows by how much the feature count has changed in the 30 days before the analysis is made - showing in a limited way current mapping dynamics.
- Percent - the 30 days trend as percentage of the feature count.