Ordnance Datum

Ordnance Datum

In the British Isles, an Ordnance Datum or OD is a vertical datum used by an ordnance survey as the basis for deriving altitudes on maps. A spot height may be expressed as AOD for "above ordnance datum". Usually mean sea level (MSL) is used for the datum. In particular:

Tunnel Datum

Tunnel Datum is a datum based on Ordnance Datum used in designing tunnels which pass below sea level. By using a lower datum as the base point, negative numbers can be avoided in calculations, eliminating a possible source of mistakes.

  • for the London Underground, a tunnel datum of ODN − 100m is used;[2] thus a depth of -60 m is 40m ATD (above tunnel datum)
  • for the Channel Tunnel, a tunnel datum of ODN − 200m is used;[3] thus a depth of -60 m is 140m ATD

References

  1. ^ a b Irish Grid Reference System from OSI website
  2. ^ "Victoria Station Upgrade Environmental Statement: Main Report" (PDF). Transport for London. 2007-11-15. pp. p.2–6; §2.5.4, fn 2. http://www.tfl.gov.uk/assets/downloads/victoria-Environmental-Statement-Main-Report.pdf. Retrieved 2008-07-28. 
  3. ^ Radcliffe, Eric (1995). "Control and Construction Surveys". In Colin J Kirkland. Engineering the Channel Tunnel. Taylor & Francis. p. 53. ISBN 0419179208. 

Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • ordnance datum — noun The standard sea level of the Ordnance Survey, now mean sea level at Newlyn, Cornwall • • • Main Entry: ↑ordnance …   Useful english dictionary

  • ordnance datum — noun Brit. the mean sea level as defined for Ordnance Survey …   English new terms dictionary

  • Amsterdam Ordnance Datum — NAP Level in Amsterdam City Hall Normaal Amsterdams Peil (NAP) or Amsterdam Ordnance Datum is a vertical datum in use in large parts of Western Europe. Originally created for use in the Netherlands, it was adopted by Prussia in 1879 under the… …   Wikipedia

  • Datum (geodesy) — Geodesy Fundamentals Geodesy · …   Wikipedia

  • Ordnance — Not to be confused with Ordinance (disambiguation). Ordnance may refer to: Military: Military logistics, especially provision of weapons and ammunition Ordnance weapon, a personal weapon issued to a member of a military unit Aircraft ordnance,… …   Wikipedia

  • ordnance — n. 1 mounted guns; cannon. 2 a branch of government service dealing esp. with military stores and materials. Phrases and idioms: ordnance datum Brit. mean sea level as defined for Ordnance Survey. Ordnance map Brit. a map produced by Ordnance… …   Useful english dictionary

  • Ordnance Survey National Grid — For the electricity network, see National Grid (Great Britain). Geodesy Fundamentals …   Wikipedia

  • Национальные системы высот в геодезии — Национальные системы высот в геодезии  принятые в разных странах стандарты для определения высоты точек на местности. Используются в любой проектной документации по строительству. Цель этой статьи описать соответствие между разными системами …   Википедия

  • Geodetic system — For other uses, see Geodetic. Geodesy Fundamentals …   Wikipedia

  • Référent altimétrique — Un référent altimétrique est, en géodésie, un point dont l altimétrie est fixée et qui sert à calculer celle des autres points. Sommaire 1 Définition 2 Exemples 3 Voir aussi 3.1 Articles c …   Wikipédia en Français

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”