Using online maps


Point and click to discover gridrefs

All the mapping systems seem to provide a point and click interface which can be used to find OS grid references.


Set the resolution you require using the icons at the bottom right of the map. Click on the map at the location you require and it will go to a new page with an arrow pointing at the location. The value you require is in the link in the blue box near the bottom of the page e.g.


Use http://www.streetmap.co.uk/streetmap.dll?G2M?X=385300&Y=398500&A=Y&Z=1 to link to this map.

Do NOT use the values in any other box!. Decode the X= and Y= co-ordinates to extract your exact grid reference, or click the here link on the next line of their page to see one accurate to 100 metres.

There is a description telling users how to use streetmaps to provide a URL pointing to an exact location.


Their point and click interface provides a zooming facility and does not provide the ability to allow you to easily determine point grid references.

Magic (England/Wales only)

There is a row of icons at the top left of the map. The left icon is a question mark on a grid. Click this icon to select the location information tool. Then click on the map at the exact point where the building is. A window then appears containing a full grid reference. This pair of numbers can be used to obtain the exact grid reference.

Extracting grid references from X/Y co-ordinates

Everybody seems to use an X=/Y= system each followed by six digits. The first digit of each identifies the 100Km square in the OS system which is represented by a pair of letters at the start of the grid reference. The remaining digits are the distance in metres in this square, the X=nnnnn holds the easting, and the Y=nnnnn hold the northing. So for a six digit reference useful for places (100 metre resolution) take the next 3 digits, and for higher (1 metre) use all five digits. e.g.


is the encoding for SU357712 (100 metre resolution) / SU3571071235 (1 metre resolution)

Google Maps

In the Genuki scripts that use Google Maps to display locations, icons are used to mark specific points. If you drag and drop these markers to new locations, a pop-up appears which displays the UK OS grid reference, or for Ireland the latitude/longitude. This is a link to a dialogue which uses our standard contact link interface to send an email to the county maintainer about the corrected location. The dialogue is only enabled for those counties in which the gazetteer or church database (according to map type) is being developed. This is defined in the county database entry.