There is an issue with the calculated w3w reference generated from the starting grid reference. It is therefore recommended to put the correct W3W reference in the event description, rather than relying on the calculated value.

Even if it calculated correctly, it could be up to 141m out because the grid reference it is calculated from covers a 100m square.

In addition to that, there is a calculation error. See below for a more detailed explanation ...

"The starting point is the grid reference as provided when the event is set up. The parameters for Streetmap are derived from the GR. The Streetmap arrow is positioned at the bottom left of the 100 metre square. There is an algorithm for the what3words lat/long calculation but it is based on the wrong values. There are two sets of lat/long values, WGS84 and OSGB36. The W3W calculation is based on OSGB36 but we should be using WGS84. If we do then the w3w square matches the GR exactly. As it stands, the w3w positioning is always wide of the mark."

As a leader of social walks for the Beds, Bucks, Northants (BBN) group I use the W3W app (As well as a 6 figure GR)to give a precise location of where my walk will start from, but when it appears on the BBN website it is a totally different 3 words. And usually somewhere where you cannot get to WHY. An example is the walk I am leading on the 24th April, "Back to Strawberry Hill for the spring chorus", the W3Ws I used which is in the centre of the car park are Sprains, clots, area but the W3Ws on the website are Forgiving, clear, body. WHY. That square is in a field 2-3 hundred yards from the car park that I am using with no vehicle access. WHYYYY. Steve Clark BBN