Height above mean sea level
elevation of a location in reference to a historic mean sea level taken as a vertical datum
Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods. Climate change and other forces can cause sea levels and elevations to vary over time.
Uses
Elevation or altitude above sea level is a standard measurement for:
Geographic locations such as towns, mountains and other landmarks.
The top of buildings and other structures.
Mining infrastructure, particularly underground.
Flying objects such as airplanes or helicopters below a transition altitude defined by local regulations.
Units and abbreviations
Elevation or altitude is generally expressed as "metres above mean sea level" in the metric system, or "feet above mean sea level" in United States customary and imperial units. Common abbreviations in English are:
AMSL – above mean sea level
AOD or AODN – above ordnance datum
ASL – above sea level
FAMSL – feet above mean sea level
FASL – feet above sea level
MAMSL – metres above mean sea level
MASL – metres above sea level
MSL – mean sea level
For elevations or altitudes, often just the abbreviation MSL is used, e.g., Mount Everest (8849 m MSL), or the reference to sea level is omitted completely, e.g., Mount Everest (8849 m).
“Height above mean sea level” enters the record as elevation of a location in reference to a historic mean sea level taken as a vertical datum. Crown Archives preserves that source wording while asking what Height, above and mean can confirm, complicate or overturn.
Why this record matters
“Height above mean sea level” is worth following because a concise public description often conceals a longer documentary argument. Here, Height, above and mean provides the most credible route into that argument.
Place names and jurisdictional language are key evidence: both can reveal earlier catalogue descriptions and overlooked record series. The source revision retrieved here is dated Jul 31, 2026. The linked authority identifier is Q6452016. None of the 0 selected statements returned an explicit reference.
Modern boundaries and familiar names can conceal earlier jurisdictions or structures that do not align with the present site. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Treat names, boundaries and functions as historically changeable. Maps, plans, inventories and administrative records can clarify what the place meant at different dates.
- Historic place names
- Jurisdictional context
- Routes into maps and plans
Contemporary maps, plans, listed-building records, estate papers and the responsible local or national archive.
Three-step research path
- Establish the record: confirm the title “Height above mean sea level”, its source revision and the description used here.
- Expand the search: follow Height above mean sea level primary sources, Height above mean sea level archive and Height research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Height above mean sea level”?
- Which authority defined the place, boundary or structure at the relevant date?
- Which earlier names or jurisdictions may reveal additional records?
Search terms from this dossier
This entry incorporates text from “Height above mean sea level” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.