Building Heights Layer Explained

The building heights layer shows indicative heights for most of the UK. Please note that the heights should only be used as a guide and we recommend an on-site survey is undertaken for more accurate measurement. There are 6 layers as follows:

  • Building Heights – AbsH2: is the absolute height of the base of the roof, that is, where the roof intersects the principal part of the building. The principal part of the building is defined as the main structure.
  • Building Heights – AbsHMax: is the absolute height of the highest point on the building and can include any structure such as chimneys, plant housings and machinery.
  • Building Heights – AbsHMin: is the absolute minimum height of the intersection of the external building walls and the underlying ground surface.
  • Building Heights - Confidence: these are assigned by the Ordnance Survey to indicate the confidence of that individual measurement, “90” indicating that some of the numbers will be missing for that particular building and “99” indicating that the accuracy has not been assessed.
  • Building Heights – RelH2: is the relative building height from the base of the building (AbsHMin) to the height of the base of the roof (AbsH2).
  • Building Heights – RelHMax: is the relative building height from the base of the building (AbsHMin) to the height of the highest point on the building (AbsHMax).
  • The diagram below shows these measurements on a standard house.

    building heights

    Please note that in some locations there maybe part coverage due to area not being completed surveyed, however it will always be > 50% coverage. Full technical details are shown here: https://www.ordnancesurvey.co.uk/docs/technical-specifications/osmm-topo-layer-bha-technical-specification.pdf

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    Written by Tom Dawson on