Key:ele

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Public-images-osm logo.svg ele
Key-ele mapnik.png
Description
Elevation of a point in metres above sea level.
Group: Properties
Used on these elements
may be used on nodesshould not be used on waysmay be used on areasuse on relations unspecified
Useful combination
Wikidata
Wikidata-logo.svgSearch Wikidata
Status: approvedPage for proposal


Elevation (height above sea level) of a point in metres. This is mainly intended for mountain peaks but could also be used for elevation of airport runways and many other objects. For OpenStreetMap, this value should be in meters above above mean sea level as defined by the EGM96 geoid model. This elevation is usually very close to national "above sea level" systems with differences < 1m. This is not the height above the WGS84 ellipsoid (see Geoid) which is shown as raw elevation by some satellite navigation devices and which can differ from geoid elevation by up to 100m.

In case of buildings and other man_made structures that stand on the ground, use the elevation of the surrounding ground, not of the structure itself (e.g. don't tag the roof top or the tip of a tower, but tag the ground level and add the height with the tag height=*).

Basics

OSM currently records points with their latitude and longitude (x/y coordinates), elevations are only recorded for features where they are significant like for peaks or surved points. Where this is done, the elevation above geoid (EGM96) is stored in the ele=* key. OpenStreetMap does not try to be a general elevation database so you should not tag elevation of nodes with no other tags and no specific meaning that suggests an elevation value is significant information in this case.

A proposal for vertical datums other than the EGM96 geoid is to store them in keys such as ele:xyz=*, where xyz is the map datum and elevation is specified in meters.

The elevation in a local datum can be tagged as ele:local=*, with elevation specified in meters.

Sources for elevation values can be signs or values from literature. Such values should however also be checked for plausibility since elevation signs and official mountain heights are known to be frequently inaccurate. Another source of elevation data is GPS traces but elevation values from these are usually much less accurate than the horizontal position. You also need to make sure values are in the correct coordinate system or converted as necessary in case of ellipsoid based elevations.

Another source of elevation data are gridded elevation data sets. Such are often used in outdoor maps to render relief, like OpenCycleMap and Reit- und Wanderkarte and elevation values can be determined from displaying these maps as a background layer in editors. Beware however that such data sets contain a significant amount of noise and errors and absolute elevation values can easily be off by 50m.

In general elevation information with sub-meter accuracy is rarely verifiable so elevations should usually be specified in integer meters.

National reference systems

Elevations posted on official signs are usually relative to the national reference system of the respective country and have to be converted to WGS84/EGM96.

Country Standard Common name Heights Tide gauge Reference point Conversion
Australia Australian Height Datum Metres above mean sea level 32 distinct tidal references points on Australian coastline. Ausgeoid09. Conversion calculator online
Austria Meter über Adria (m ü. Adria)
(meters above Adriatic)
Normal-orthometric Trieste 1875 Hutbiegl
Belgium meter boven Oostends Peil (m O.P.)
(meters above Oostende tide gauge)
Orthometric Ostende Ostende
Czech Republic Bpv (Baltic Sea vertical datum) metrů nad mořem (m n.m.)
(meters above sea level)
Normal (Molodenskii's) Kronstadt Kronstadt, Russia
Estonia BK77 Normal Kronstadt Kronstadt [1]
Finland N43,N60,N2000 Orthometric Helsinki Helsinki [2]
France (mainland) NGF-IGN69 mètres au-dessus du niveau de la mer (m)
(meters above sea level)
Normal Marseille Marseille [3]
France (Corsica) NGF-IGN78 mètres au-dessus du niveau de la mer (m)
(meters above sea level)
Normal Ajaccio Ajaccio [4]
Germany *)[1] DHHN92 Meter über Normalhöhennull (m ü. NHN) Normal Amsterdam Wallenhorst
Former West Germany *) DHHN12 Meter über Normalnull Normal-orthometric Amsterdam Hoppegarten (near Müncheberg)
Former East Germany *) SNN76 Meter über Höhennull (m ü. HN) Normal Kronštadt Hoppegarten (near Müncheberg)
Hungary Tengerszint feletti magasság Normal Kronštadt Nadap
Ireland meters above sea level (m ASL / m a.s.l.) Orthometric Malin Head Malin Head
Italy metri sul livello del mare (m s.l.m.)
(meters above sea level)
Orthometric Genoa Genoa
Japan **) Tōkyō-wan heikin kaimen (東京湾平均海面)
(Tokyo Peil, T.P.)
Orthometric Chiyoda, Tokyo Nihon suijin genten (日本水準原点), 24.3900m **)
Liechtenstein LN02 Meter über Meer (m ü. M.)
(meters above sea level)
Marseille Geneva
Luxemburg Orthometric Amsterdam Amsterdam
Netherlands meter boven/onder NAP (m NAP) (meters above/under NAP) Orthometric Amsterdam Amsterdam
Norway meter over havet (moh.)
(meters above sea level)
Normal-orthometric Tregde Tregde
Poland metry nad poziomem morza (m n.p.m.) Normal Kronštadt
Portugal Nível Médio das Águas do Mar Orthometric Cascais Cascais
Russia BS1977 vysota (metry) nad urovnem morja
(высота (метры) над уровнем моря)
(elevation/meters above sea level)
Normal Kronstadt Kronstadt The pseudo-geoid model EGM2008BALT is available for St. Petersburg / Kronstadt area [5]
Slovakia metrov nad morom (m n.m.)
(meters above sea level)
Normal Kronštadt
Slovenia Normal-orthometric Trieste 1900 Ruse
Spain metros sobre el nivel del mar (msnm)
(meters above sea level)
Orthometric Alicante Alicante
Sweden RH2000 Meter över havet (m ö.h.)
(meters above sea level)
Normal Amsterdam
Switzerland ***) [2] LN02 Meter über Meer (m ü. M.)
(meters above sea level)
Marseille Geneva
Turkey Normal-orthometric Antalya Antalya
UK - Great Britain Ordnance Datum Newlyn meters above sea level (m ASL / m a.s.l.) Orthometric Newlyn, 1915 to 1921 Newlyn OSGM02, Coordinate transformer
UK - Northern Ireland Belfast Ordnance Datum meters above sea level (m ASL / m a.s.l.) Orthometric Clarendon Lock, Belfast, 1951 to 1956. Clarendon Lock, Belfast
Former Yugoslavia Nadmorska visina (m/nv, ~meters above Adriatic) Normal-orthometric Trieste 1875/1900

*) DHHN92 was adopted gradually after reunification. Even newer topograpic maps may still use the former reference systems.
Former East Germany used DHHN-12 on the territory of East Berlin, in rail contexts and for landlocked waterbodies.

**) National authorities use this datum only for the four main islands of Hokkaidō, Honshū, Shikoku, Kyūshū and associated islands. For Sado, Oki, Tsushima, as well as for the Izu, Ogasawara and Ryūkyū islands, the mean sea level of a nearby coast or bay is used. For example, the reference point for Miyake-jima, which belongs to the Izu islands, is the mean sea level of Ako Bay on the western coast of the island.

***) LN02 remains in force. For LHN95, which uses orthometric elevations, the reference altitude of Repère Pierre du Niton was kept. [3]

Example

The height of Breithorn in Switzerland is 4,164 metres. It could be mapped as:

natural=peak
name=Breithorn
ele=4164

The height of rail tracks in Tanggula railway station is 5,068 meters. It could be mapped as:

railway=station
name=唐古拉
name:bo=གདང་ལ་།
name:en=Tanggula
name:zh=唐古拉
ele=5068

Local units

It's been noted that some elevations are more conspicuous than others, and the requirement that key:ele be in meters is unhelpful for denotation on mountain peaks in non-metric areas. Since locals in the United States (and certainly elsewhere) think of things like mountain elevations strictly in feet, there seems to be no good way to address this with the current framework.

  • It's tempting to enter an elevation with a unit of measure ("3045 feet") but the tag must be in metres
  • It's reasonably (likely?) that software relies on this tag being numeric metres
  • Renderers have no way of doing conversions on the fly to local units while creating image tiles

There is likely no good solutions to this, at least in the short term.

See also

  • layer=* - used to mark layering of map elements
  • height=* - used to mark how tall a map object is
  • alt=* - Proposal to mark exact altitudes concerning to the reference system of heights. Deprecated.
  • man_made=survey_point

References

  1. Bundesamt für Kartographie und Geodäsie (BKG):Höhenreferenzsysteme in Deutschland.
  2. http://www.swisstopo.admin.ch/internet/swisstopo/de/home/topics/survey/networks/ln02.html
  3. http://www.swisstopo.admin.ch/internet/swisstopo/en/home/topics/survey/networks/lhn95.html