What's AOD?
AOD stands for Above Ordnance Datum. The Ordnance Datum is the basis for all the land heights that appear on Ordnance Survey maps. It is essentially the mean sea level at Newlyn in Cornwall, and is sometimes called Ordnance Datum Newlyn (ODN).
But this site normally shows “London Bridge” heights. What are those?
The tide heights that I have shown on this site until now represent the depth of water above Chart Datum at London Bridge. It’s a common measure in all Thames tidal information, and many users of the river are familiar with it. Chart Datum (CD) is roughly the lowest possible tide level in ‘average’ weather conditions. There is a chart datum for every stretch of the river, but in practice the local datums, e.g. Chiswick or Brentford, are not often used. I have therefore quoted the London Bridge CD heights on this site, and I will continue to do so.
By the way, the times and heights described here and elsewhere as "London Bridge" actually refer to Tower Pier.
Why have you added the AOD heights?
What I wanted was to express the predicted tidal height in a way that is meaningful to riverside residents and visitors, so that they can see more directly how the tide is likely to affect them. AOD heights are shown on very-large-scale maps, which are now freely available online on various local council websites. I have started listing known riverside AOD heights on this site (see below), and will include AOD tidal predictions from 1 Jan 2020.
How do you calculate the AOD heights?
I take the PLA predictions for Chelsea Bridge and Richmond Lock, and then estimate the heights and times for the intermediate points such as Putney, Chiswick, etc. according to distance and to the typical speed profile of a high tide. This calculation is done separately for each high tide.
LIST OF KNOWN AOD LAND HEIGHTS
This is a list of some AOD land heights, initially for Putney and Chiswick. It will be expanded and made more accessible shortly. Locations are in the middle of the carriageway unless otherwise noted. o/s = outside.
Putney Embankment going upstream from Putney Bridge
Junction with Thames Place (corner of Star & Garter Mansions): 5.1m
50m upstream of Duke's Head (o/s garage door): 4.3m
Junction with Glendarvon Street (o/s no.4 Embankment): 4.2m
o/s Dulwich College Boat House: 3.9m
o/s Imperial College Boat Club: 3.9m
North-west of Festing Road junction, o/s Leader's Gardens: 4.1m, then 4.3m opposite café, then 4.7m at junction with Ashlone Road (shortly before Beverley Brook).
o/s 5th Putney Sea Scouts hut: 4.6m, and another 4.6m 100m upstream
o/s Barn Elms Boat House: 4.3m
Chiswick Mall
At junction with Church Street, opposite slipway, near slipway edge of carriageway: 4.9m
o/s Eynham House: 4.0m
At junction with Chiswick Lane South: 4.1m
(Also benchmark on brewery wall 4.70 m )
o/s West boundary of Oak Cottage: 4.2m
o/s Strawberry House: 4.7m
In line with footway at east of The Osiers, in line with The Cottage: 4.5m
o/s Island House: 4.3m
o/s entrance to Miller's Court: 5.5m
Strand-on-the-Green
Carriageway o/s Pier House (just W of road humps): 4.9m
Towpath o/s The Bull's Head: 4.3m
Towpath o/s no. 60 Strand-on-the-Green: 4.3m
Towpath o/s 9/10 Magnolia Wharf: 4.0m
Richard Jennings
last updated 13 Sep 2021