Proposed features/key:prominence

From OpenStreetMap Wiki
Jump to: navigation, search
key:prominence
Status: Proposed (under way)
Proposed by: jeisenbe
Tagging: prominence=*
Applies to: node
Definition: Topographic prominence of a peak in meters
Rendered as: Not rendered
Drafted on: 2009-09-28
RFC start: 2018-09-24

Proposal

Use the tag prominence=* to specify the Topographic prominence of a natural=peak in meters.

Rationale

Topographic prominence is a objective measurement of how significant a peak is. For example, lists of tallest mountains use a minimum prominence cutoff of 100, 200 or 300 meters to define an independent peak. In general, all peaks with very high prominence (over 1500 meters) are important mountains. But not all important peaks have high prominence.

Prominence might be used to select peaks for rendering, or to select significant peaks for analysis by database users. A scheme which can work both for Denmark and Switzerland, would be: If too many peaks are present within a particular area of the map at a certain zoom level, select the ones with highest prominence. Different thresholds might be used for when to render a peak symbol only, versus render the peak with a name label or elevation.

The prominence of a peak is the same as its elevation if it is the highest point on a continent or island. All other peaks on the same landmass have a prominence that is lower than their elevation, found by subtracting the elevation of the lowest saddle (also called the "key col") along the ridge that connects to the next higher mountain.

An introduction to Topographic Prominence

Tagging

Use the tag prominence=* together with natural=peak and ele=*. This number, in meters, may be directly calculated by subtracting the elevation of the key saddle (or "key col") from the elevation of the peak.

For most peaks, it's only necessary to know the elevation of the nearby saddles and peaks to find the prominence of a peak. Walk to the top of the peak and record the elevation. Look around and find any taller nearby peaks. If there is only 1 taller hill, walk down the ridge line to the lowest point between the first hill and the taller hill, then record the saddle elevation.

The prominence of the first peak is the elevation of the first peak minus the elevation of the saddle.

See this article for more details: An introduction to Topographic Prominence

Example

  • natural= peak
  • name= Mont Blanc
  • name:it= Monte Bianco
  • name:fr= Mont Blanc
  • ele= 4810.90
  • prominence=4695
  • source= Opentopomap / SRTM

Tagging Errors

Do not copy prominence data from Peaklist.org or Peakbagger.com without permission.

Please list the prominence in meters, not in feet or other units.

Features/Pages Affected

natural=peak It is proposed that this tag, prominence=* be included on the Wiki page for natural=peak as an additional tag

natural=saddle On the page for natural=saddle it will be mentioned that the elevation of a key saddle can be used to calculate the prominence of a peak.

Further extension

A Relation peak:prominence may be define to relate a peak to its "key col" and to its "parent peak". See the discussion page for an example. This relation is not a formal part of this proposal.

Further Discussion

To the talk page please.

This tag was discussed recently (September 2018) in the Tagging mailing list: https://lists.openstreetmap.org/pipermail/tagging/2018-September/

This feature was originally proposed on 2009-09-28 by user [User:hjelmis|hjelmis], and has been in use since that time, though it had not been brought to a vote.