Tag:ele

Data quality ⓘ and volume ⓘ
2022-02-16 ele=*

Elevation of the feature relative to sea level in meters
TopographyPhysical Geography
Tag level ⓘ	secondary
Tag type ⓘ	quantitative
Geometry conventions ⓘ	mixed
Closed way default ⓘ
Way direction significant ⓘ	no

Consistency:	excellent
Verifiability:	🞼	+	+
Feature count:	2.26M	19.6k	5.38M
Number of nodes:	2.26M	531k	90.9M
Nodes per feature:	–	27.1	16.9
Average segment length:	–	147m	9m
Total size (in km/km²):	–	25.0k	1.44M
Taginfo numbers and trends ⓘ

Counts:	2.26M	5.26M	140k
30 days trend:	4094	3597	288
⮡ Percent:	0.18	0.07	0.21

The tag ele=* is used to map the elevation of a feature relative to sea level.

ele=* essentially adds a third dimension coordinate to features in the OSM database.

Primary tags

The tag is used mostly together with the following primary tags:

building=* (58 percent)
natural=peak (7.07 percent)
natural=water (6.56 percent)
man_made=survey_point (2.79 percent)
amenity=place_of_worship (2.24 percent)
place=hamlet (1.91 percent)
amenity=school (1.82 percent)
tourism=information (1.32 percent)
amenity=grave_yard (1.09 percent)

There are some, less frequently used, primary tags not in the above list where a significant percentage of features are mapped with an ele=* tag. Specifically:

Secondary tags

There are a few tags that are used as secondary tags to ele=* as well though none of them is particularly widespread in use. Those are:

Consistency in use

Overall consistency in use of the tag is excellent. Elevation values are occasionally specified in feet rather than meters. This is however overall fairly rare. Most of the uses of the tag specify a numerical value - matching the regular expression ^-?\d{1,4}(\.\d+)?$ that is used by OSM-Carto. Not exclusively numerical values are most commonly of the forms:

^-?\d{1,4}(\.\d+)?\s*(ft|feet)$ - 944 features
^-?\d{1,4}(\.\d+)?\s*(m|meters?)$ - 1419 features
^-?\d{1,4}(\.\d+)?;-?\d{1,4}(\.\d+)$ (that is two semicolon separated values) - 268 features
other forms not matching ^-?\d{1,4}(\.\d+)?$ - 3460 features

Another source of smaller inconsistencies is that elevations are specified based on different reference geoids.

Value accuracy

The accuracy of elevation values tagged is typically good but varies quite a bit depending on how the values were determined. Values van be pretty far off when elevations of peaks for example are tagged based on some seemingly authoritive sources, sometimes by several hundred meters. Values determined from digital elevation models depend on the model used and for peaks often understate the elevation systematically. For many of the imported buildings the elevation values are fairly accurate as they are often determined from high resolution local measurements.

Verifiability

Verifiability of ele=* is excellent when applied to nodes. This is more of a problem for lines and polygons - unless those are constant elevation like in case of lakes.

Completeness

None of the feature types the ele=* tag is used on applies this tag with a very high level of completeness. The highest percentages can be found on natural=peak, natural=volcano and natural=hill.

History of use

A large fraction of the ele=* values in the OpenStreetMap database comes from data imports. This in particular applies to almost all of the buildings. Manual mapping is more widespread for natural=peak and natural=water. Also quite a significant fraction of features have an elevation value automatically determined from digital elevation data sets.